The government has unveiled its new points-based immigration system, due to come into force in 2021, we break down what it means for the UK startup sector

Startups moving to the scale-up phase will naturally experience growing pains, here's how to manage your team through that period with as little disruption as possible

Many startups in Britain either do not intend to or cannot access the government's Coronavirus Business Interruption and Loan Scheme, and may be forced to respond with furloughs or layoffs, warns a report

The new rule, which will force payments platforms and online retailers to strongly authenticate purchases of £28 or more has been delayed by another six months amidst the COVID-19 pandemic

The challenger brand launched by the high street bank will be shutting down after informing customers that it is closing down the app-only bank

Changfeng Gui, Kelei Wang and Jucheng Wei
Trans. Amer. Math. Soc. 373 (2020), 3649-3668.
Abstract, references and article information

Noah Taylor
Trans. Amer. Math. Soc. 373 (2020), 3541-3559.
Abstract, references and article information

Mahbub Alam and Anish Ghosh
Trans. Amer. Math. Soc. 373 (2020), 3357-3374.
Abstract, references and article information

Boris Adamczewski, Julien Cassaigne and Marion Le Gonidec
Trans. Amer. Math. Soc. 373 (2020), 3085-3115.
Abstract, references and article information

V. M. Radchenko and N. O. Stefans’ka
Theor. Probability and Math. Statist. 99 (2020), 229-238.
Abstract, references and article information

M. V. Pratsiovytyi and S. P. Ratushniak
Theor. Probability and Math. Statist. 99 (2020), 211-228.
Abstract, references and article information

S. S. Lohvinenko and K. V. Ralchenko
Theor. Probability and Math. Statist. 99 (2020), 149-168.
Abstract, references and article information

Yu. V. Kozachenko and I. V. Rozora
Theor. Probability and Math. Statist. 99 (2020), 113-124.
Abstract, references and article information

D. V. Gusak and E. V. Karnaukh
Theor. Probability and Math. Statist. 99 (2020), 77-89.
Abstract, references and article information

O. D. Borysenko and D. O. Borysenko
Theor. Probability and Math. Statist. 99 (2020), 67-75.
Abstract, references and article information

A. Seesanea and I. E. Verbitsky
St. Petersburg Math. J. 31 (2020), 557-572.
Abstract, references and article information

N. Kuznetsov
St. Petersburg Math. J. 31 (2020), 521-531.
Abstract, references and article information

G. Kresin and V. Maz'ya
St. Petersburg Math. J. 31 (2020), 495-507.
Abstract, references and article information

Xiaodong Cao, Bennett Chow and Yongjia Zhang
Proc. Amer. Math. Soc. 148 (2020), 2595-2600.
Abstract, references and article information

Bin Li and Jieqiong Shen
Proc. Amer. Math. Soc. 148 (2020), 2565-2578.
Abstract, references and article information

Liz Vivas
Proc. Amer. Math. Soc. 148 (2020), 2525-2537.
Abstract, references and article information

In response to a media report, Police today dismissed allegations that Commissioner of Police Tang Ping-keung turned a blind eye to unauthorised building works at a flat he rented.

The force expressed regret over the unfounded report and said that its content deviated from the facts.

Mr Tang rented a unit on Broadcast Drive in Kowloon Tong in 2016 and was notified by the Buildings Department in 2017 that there were unauthorised building works on the unit’s rooftop that must be removed.

He immediately informed the owner of the removal order and requested him to handle the matter. The owner has not complied with the order.

Mr Tang moved out of the unit in June 2019, Police added.

In view of the severe economic repercussions caused by the COVID-19 pandemic globally and locally, the Government announced another package of measures to support the affected individuals and businesses last Wednesday. Two of which are particularly relevant to the legal and dispute resolution sector - the LawTech Fund and the COVID-19 Online Dispute Resolution (ODR) Scheme. The LawTech Fund was briefly introduced in this blog a few days ago. Today, I would like to give an online explanation of the COVID-19 ODR.

In anticipation of an upsurge of disputes arising from or relating to COVID-19, the scheme aims to provide speedy and cost-effective means to resolve such disputes, especially for those involving micro, small and medium-sized enterprises (MSMEs) that may be adversely affected or hard hit by the pandemic. The scheme will engage eBRAM (electronic Business Related Arbitration & Mediation system) to provide ODR services to the general public and businesses, in particular MSMEs, involved in low value disputes.

The scheme plans to cover COVID-19 related disputes with the claim amount for each case to be capped at $500,000. Either one of the parties (claimant or respondent) must be a Hong Kong resident or company and they will only be required to each pay $200 registration fees. Under the scheme, the parties are required to enter into a dispute resolution agreement to record their consent.

The process to be adopted is a multi-tiered dispute resolution mechanism where the parties will first attempt to negotiate their disputes, followed by mediation and if that does not result in settlement, then subsequently to arbitration for a final and binding award. This is in line with the "Mediate First" policy that we have been advocating under our "Mediate First" Pledge Programmes.

The scheme aims to offer a fast and effective means to resolve disputes among parties. Each tier of dispute resolution will be conducted within a limited time. The tiers are devised with a view to avoiding disputes and differences from being entrenched. If the disputes can be resolved successfully and amicably through negotiation or mediation, we hope it will help build and reinforce a harmonious society and enable the parties to preserve their long term business relationship.

We also hope the scheme will have the benefit of job creation and job advancement for mediators and arbitrators (including their pupils). Parties are at liberty to appoint the third party neutral of their choice and if no agreement is reached, there will be a mechanism for appointment. The third party neutrals and the parties or their representatives can still handle cases under the social distancing measures online and indeed to practice on the handling of cases online. We would like the scheme to be launched in June if funding is provided in April.

It is a global trend to develop and use ODR to provide reliable and efficient platform to facilitate alternative dispute resolution. The scheme is in line with the development under Asia-Pacific Economic Cooperation's Collaborative Framework on ODR (APEC Framework), with MSMEs as the major beneficiary. The mechanism of adopting negotiation and mediation in the first stage under the APEC Framework is also to prevent entrenched views on the conflicts, thereby helping to create harmony in society.

Some forms of alternative dispute resolution, such as mediation, are a more cost-effective way to resolve disputes. The costs of mediation are almost always lower than the disputed amounts, making it an economical way to resolve disputes. Mediation can save time too. Some cases may be resolved following just one day of mediation.

LawTech has greatly helped the development of dispute resolution services. The establishment of a safe, reliable and credible platform to provide enterprises with convenient and cost-effective online dispute resolution will become a new trend.

It is one of the major long-term policy objectives of the Department of Justice (DoJ) in recent years to enhance and promote Hong Kong's status as an international legal hub for deal-making and dispute resolution. A further promotion of the use of ODR will help consolidate Hong Kong's position as an international business and financial centre.

The social media accounts of the DoJ's IDAR Office have been introducing the procedure, characteristics and benefits of mediation and arbitration. You may wish to visit the dedicated pages of the IDAR Office to keep abreast of the dispute resolution services.

In addition to the relief measures announced by the Government, the DoJ has also taken the initiative to speed up payment of fees to counsel. Counsel engaged by the DoJ could submit their interim fee notes together with the interim case reports after certain work has been completed. Each case will be considered individually on a case-by-case basis and interim payments could be made. I have enquired and am also glad to learn from the Legal Aid Department and the Duty Lawyer Service that they made similar arrangements.

We are confident that Hong Kong can weather the storm with our fundamental strengths and resilience. We also trust that we would overcome this unprecedented challenge by standing in solidarity.

Secretary for Justice Teresa Cheng wrote this article and posted it on her blog on April 13.

The Department of Justice (DoJ) is responsible for making prosecutorial decisions. At times, these decisions attract extensive discussions in the community. It becomes interesting when overseas media and politicians embark upon allegations or purported demands relating to Hong Kong’s prosecutorial decisions.

Article 63 of the Basic Law provides that the DoJ of the Hong Kong Special Administrative Region shall control criminal prosecutions, free from any interference. This prosecutorial independence ought to be a feature in any society that cherishes the rule of law, and therefore attempts made by jurisdictions requesting such decisions to be made one way or another or even to request that they be varied is a blatant defiance of rule of law.

The DoJ acts independently without political, improper or undue influence, including those from public opinions and certainly not from overseas politicians who made these requests possibly not based on evidence or law but on political motives.

In cases in which legal proceedings are ongoing, we will not comment and neither should others as it may bring about the undesirable effect of a trial by the public. Statements made requesting the DoJ to drop all the charges or uttered with a view to affecting the DoJ’s role in controlling criminal prosecutions are futile. It is plainly wrong to label our prosecutions as politicised. On the contrary, no one, be they tycoons or politicians, will be above the law or be treated differently simply because they have a certain status or are pursuing certain beliefs or goals.

When law enforcement agencies have completed their investigation, they would seek legal advice from the DoJ. Our prosecutors would carefully consider the investigation reports and relevant materials submitted. A prosecution would only be commenced if the prosecutor is satisfied that there is sufficient admissible evidence to support a reasonable prospect of conviction.

The well-established procedures of our criminal justice system include the independent investigations by law enforcement agencies, the independent prosecutorial decisions based on objective assessment of evidence, applicable laws and in accordance with the Prosecution Code, and finally open trials by our independent judiciary. If we are to accede or be seen to yield to unreasonable demands to drop charges irresponsibly, we would not only be unfair and unprofessional but would also act in violation of the spirit of the rule of law.

I have explained the DoJ’s prosecution procedure on various occasions and stressed that our prosecutors are expected to apply the highest of professional standards in handling all criminal cases impartially and without fear or favour. They must not be influenced by political consideration. Cases should not be handled any differently irrespective of one’s own political beliefs or opinions.

The Hong Kong Special Administrative Region Government always respects and protects human rights and freedoms. However, these rights are not absolute. As pointed out by the Chief Justice of the Court of Final Appeal at the Ceremonial Opening of the Legal Year 2020: “It is important to understand that the enjoyment of these rights has limits so as not to affect adversely to an unacceptable level the enjoyment by other members of their community of their rights and liberties.” There are clear limits in the law to the exercise of these rights. When law is broken, action will be taken in accordance with the criminal justice system.

The rule of law is a core value in Hong Kong. We have to stand united in upholding our independent criminal justice system especially when it is under attack by any unfair and unfounded allegation made with a view to discrediting or undermining it. Any attempt to do so would only be attractive to those unfamiliar with our independent legal and judicial systems. We are obliged to continue to explain and ensure that their absence of knowledge would not override facts. We will continue to disseminate proper and accurate information and help clear any misunderstandings in the local and overseas communities.

Secretary for Justice Teresa Cheng wrote this article and posted it on her blog on April 26.

Why did the undergraduates cross the road? Extra credit. In concept as well as in practice, I have never understood extra credit. As someone who was home-schooled by a former Catholic high-school principal, “extra credit” was never a part of … Continue reading →

Let’s discuss student opinion forms, course evaluations, student evaluation of teaching forms, whatever term you use. Article after article year after year highlight how toxic they are. More recently the emphasis has been on how they differ according to instructor … Continue reading →

The confidence level of Hong Kong’s exporters has fallen to its lowest-ever level in the face of a triple challenge – the COVID-19 outbreak, softening global demand and lingering trade tension between the United States and Mainland...

Ryan A. Ristau
Nov 1, 2013; 26:211-215
From Research to Practice

Katherine S. O’Neal
Nov 1, 2016; 29:249-252
Pharmacy and Therapeutics

The Hong Kong Special Administrative Region Government has rejected allegations made by certain officials and politicians in the United States, United Kingdom and European Parliament relating to an April 18 arrest operation and other security matters.

In a statement today, the Hong Kong SAR Government said such allegations were totally unfounded and amounted to a serious intervention in Hong Kong's affairs.

The SAR Government strongly disagreed with the grossly irresponsible remarks and expressed deep regret about them.

It pointed out that since its return to the Motherland, the HKSAR has maintained stability and prosperity under the principle of "one country, two systems", exercising "Hong Kong people administering Hong Kong" and a high degree of autonomy in strict accordance with the Basic Law (BL).   

"The Central Government has time and again reiterated that it will unswervingly implement the policy of one country, two systems' and make sure that it is fully applied in Hong Kong without being bent or distorted. 

“How to implement the policy in the HKSAR - an inalienable part of the People's Republic of China (BL Article 1) and a local administrative region of the People's Republic of China which shall enjoy a high degree of autonomy and come directly under the Central People's Government (BL Article 12) - are entirely internal affairs of the People's Republic of China.

“No other state has the right to intervene, directly or indirectly, in those internal affairs.”

The statement noted Hong Kong people enjoy extensive rights and freedoms which are enshrined in the Basic Law. Basic Law Article 4 states that the HKSAR shall safeguard the rights and freedoms of the residents and of other persons in the region in accordance with law. 

“In addition, human rights and freedoms in Hong Kong are fully protected by the Hong Kong Bill of Rights Ordinance and other legislation, and underpinned by an independent judiciary."

The SAR Government said it always respects and protects human rights and freedoms. Any allegation that there has been an erosion in freedoms enjoyed by Hong Kong people is unfounded.

However, these rights are not absolute. As pointed out by the Chief Justice of the Court of Final Appeal at the Ceremonial Opening of the Legal Year 2020: "It is important to understand that the enjoyment of these rights has limits so as not to affect adversely to an unacceptable level the enjoyment by other members of their community of their rights and liberties."

There are clear limits in the law as to the exercise of these rights. When the law is broken, action will be taken in accordance with the criminal justice system.

"We therefore take great exception to comments made by officials and politicians in foreign countries concerning the recent arrests and prosecution of a number of persons for organising and participating in unauthorised assemblies in Hong Kong. 

“The allegation by some that those arrests amounted to an attack on Hong Kong's freedoms and a breach of the BL is absurd and can hardly stand the test of any law-abiding jurisdiction," the statement emphasised.

It also pointed out that Basic Law Article 63 provides that "The Department of Justice of the Hong Kong Special Administrative Region shall control criminal prosecutions, free from any interference." 

Prosecutors have always been discharging this constitutional duty independently and professionally, without fear or favour. Prosecutorial decisions are based on an objective assessment of all admissible evidence and applicable laws, made strictly in accordance with the Prosecution Code which is available to the public.

Cases will not be handled any differently owing to the political beliefs or background of the persons involved.

When law enforcement agencies have completed their investigation, they would seek legal advice from the Department of Justice. The prosecutors would carefully consider the investigation reports and relevant materials submitted. A prosecution would only be commenced if the prosecutor is satisfied that there is sufficient admissible evidence to support a reasonable prospect of conviction.

In short, the well-established procedures of Hong Kong's criminal justice system include the independent investigations by law enforcement agencies, the independent prosecutorial decisions based on the objective assessment of evidence, applicable laws and in accordance with the Prosecution Code, and finally, open trials by an independent judiciary. 

"The guarantee of judicial independence is explicitly set out in the BL and the quality of the judgments of our courts contributes to the much respected judiciary and rule of law in the HKSAR.

"We therefore note with abhorrence certain overseas politicians' request that the HKSAR Government should drop the charges against the arrested individuals. If we were to accede or to be seen to yield to such unreasonable demands, we would not only be unfair and unprofessional but would also act in violation of the spirit of the rule of law – a core value in Hong Kong," the statement added.

The SAR Government remains steadfast to uphold the rule of law. The latest Rule of Law Index 2020 released by the World Justice Project, in which Hong Kong maintains its ranking as No. 5 in the East Asia and Pacific Region and No. 16 globally, several places ahead of the United States, has clearly affirmed Hong Kong's commitment.

On legislating for Basic Law Article 23, the statement said, "The HKSAR Government has the constitutional duty to ensure that the necessary legislation is in place to safeguard national security.

“Having laws in place to protect national security is common in many jurisdictions, and we do not see how any defence of sovereignty and security by a jurisdiction would impact on its local and overseas investment. 

“Coincidentally, it is relevant to note security issues arising from the social unrest last year were part of the causes affecting Hong Kong's score under 'Investment Freedom' according to the US-based Heritage Foundation 2020 Index of Economic Freedom."

As regards enquiries about the role of the Hong Kong & Macao Affairs Office of the State Council (HKMAO) and the Liaison Office of the Central People's Government (LOCPG) in the HKSAR, they represent the Central People's Government to which the HKSAR comes directly under pertaining to Basic Law Article 12. 

These offices have the power and responsibility over the proper and full implementation of the Basic Law and "one country, two systems" in Hong Kong.

It is therefore clearly legitimate for the HKMAO and LOCPG to recently express their concerns over the prolonged paralysis of the Legislative Council House Committee, thereby hindering LegCo's performance of its legislative functions under the Basic Law.

"Any suggestion that those legitimate remarks by the HKMAO and the LOCPG amount to interference only illustrates an ignorance of the constitutional order of the HKSAR and its relationship with the Central Authorities," the SAR Government added.

(Dartmouth College) Annual award supports the research and teaching careers of talented young faculty in the chemical sciences.

(Ecole Polytechnique Fédérale de Lausanne) EPFL chemists have developed sponges to capture various target substances, like gold, mercury and lead, dissolved in solution. The sponges are actually porous crystals called metal organic frameworks, and now one exists for capturing toxic hexavalent chromium from water.

The Government will distribute free reusable face masks to all Hong Kong citizens, the Innovation & Technology Bureau announced today.

The CuMask, made with six layers and special ergonomic features, was developed by the Hong Kong Research Institute of Textiles & Apparel.

Two of its layers contain copper which is capable of immobilising bacteria, common viruses and other harmful substances.

The mask complies with the American Society for Testing & Materials F2100 Level 1 Standard in terms of particle and bacterial filtration efficiency, resistance to penetration by synthetic blood, and flammability and pressure resistance.

It is also reusable for up to 60 washes.

The bureau said, except for babies and infants, all holders of valid Hong Kong identity cards are eligible to obtain a mask.

Citizens can register online from 7am tomorrow till June 6. Each registration can cater for a maximum of six persons.

Upon successful registration, the mask will be delivered to the door by Hongkong Post within two weeks.

Primary and kindergarten students will each be given two masks, which will be delivered directly to children's schools. Parents do not have to register.

The Government has also arranged to deliver over 140,000 of the masks to residential homes and social welfare institutions for their distribution to those including elderly and the homeless.

Click here for registration details.

"In his new book--The Math of Life & Death: 7 Mathematical Principles that Shape Our Lives--mathematician Kit Yates makes complex mathematical concepts easily accessible to anyone, and which can improve decision making in an increasingly quantitative society. In this Q&A, Yates discusses why math is relevant to everyday life." See "Mathematician Kit Yates on Anti Vaxxer Movement, Air Travel Germs and Samoa's Measles Outbreak," by Meredith Wold Schizer, Newsweek, December 23, 2019.

Previous studies have shown that sphingosine kinase interacting protein (SKIP) inhibits sphingosine kinase (SK) function in fibroblasts. SK phosphorylates sphingosine producing the potent signaling molecule sphingosine-1-phosphate (S1P). SKIP gene (SPHKAP) expression is silenced by hypermethylation of its promoter in acute myeloid leukemia (AML). However, why SKIP activity is silenced in primary AML cells is unclear. Here, we investigated the consequences of SKIP down-regulation in AML primary cells and the effects of SKIP re-expression in leukemic cell lines. Using targeted ultra-HPLC-tandem MS (UPLC-MS/MS), we measured sphingolipids (including S1P and ceramides) in AML and control cells. Primary AML cells had significantly lower SK activity and intracellular S1P concentrations than control cells, and SKIP-transfected leukemia cell lines exhibited increased SK activity. These findings show that SKIP re-expression enhances SK activity in leukemia cells. Furthermore, other bioactive sphingolipids such as ceramide were also down-regulated in primary AML cells. Of note, SKIP re-expression in leukemia cells increased ceramide levels 2-fold, inactivated the key signaling protein extracellular signal-regulated kinase, and increased apoptosis following serum deprivation or chemotherapy. These results indicate that SKIP down-regulation in AML reduces SK activity and ceramide levels, an effect that ultimately inhibits apoptosis in leukemia cells. The findings of our study contrast with previous results indicating that SKIP inhibits SK function in fibroblasts and therefore challenge the notion that SKIP always inhibits SK activity.

The transcription factor forkhead box P3 (FOXP3) is a biomarker for regulatory T cells and can also be expressed in cancer cells, but its function in cancer appears to be divergent. The role of hepatocyte-expressed FOXP3 in hepatocellular carcinoma (HCC) is unknown. Here, we collected tumor samples and clinical information from 115 HCC patients and used five human cancer cell lines. We examined FOXP3 mRNA sequences for mutations, used a luciferase assay to assess promoter activities of FOXP3's target genes, and employed mouse tumor models to confirm in vitro results. We detected mutations in the FKH domain of FOXP3 mRNAs in 33% of the HCC tumor tissues, but in none of the adjacent nontumor tissues. None of the mutations occurred at high frequency, indicating that they occurred randomly. Notably, the mutations were not detected in the corresponding regions of FOXP3 genomic DNA, and many of them resulted in amino acid substitutions in the FKH region, altering FOXP3's subcellular localization. FOXP3 delocalization from the nucleus to the cytoplasm caused loss of transcriptional regulation of its target genes, inactivated its tumor-inhibitory capability, and changed cellular responses to histone deacetylase (HDAC) inhibitors. More complex FKH mutations appeared to be associated with worse prognosis in HCC patients. We conclude that mutations in the FKH domain of FOXP3 mRNA frequently occur in HCC and that these mutations are caused by errors in transcription and are not derived from genomic DNA mutations. Our results suggest that transcriptional mutagenesis of FOXP3 plays a role in HCC.

Prostate cancer (PCa) cells heavily rely on an active androgen receptor (AR) pathway for their survival. Enzalutamide (MDV3100) is a second-generation antiandrogenic drug that was approved by the Food and Drug Administration in 2012 to treat patients with castration-resistant prostate cancer (CRPC). However, emergence of resistance against this drug is inevitable, and it has been a major challenge to develop interventions that help manage enzalutamide-resistant CRPC. Erythropoietin-producing human hepatocellular (Eph) receptors are targeted by ephrin protein ligands and have a broad range of functions. Increasing evidence indicates that this signaling pathway plays an important role in tumorigenesis. Overexpression of EPH receptor B4 (EPHB4) has been observed in multiple types of cancer, being closely associated with proliferation, invasion, and metastasis of tumors. Here, using RNA-Seq analyses of clinical and preclinical samples, along with several biochemical and molecular methods, we report that enzalutamide-resistant PCa requires an active EPHB4 pathway that supports drug resistance of this tumor type. Using a small kinase inhibitor and RNAi-based gene silencing to disrupt EPHB4 activity, we found that these disruptions re-sensitize enzalutamide-resistant PCa to the drug both in vitro and in vivo. Mechanistically, we found that EPHB4 stimulates the AR by inducing proto-oncogene c-Myc (c-Myc) expression. Taken together, these results provide critical insight into the mechanism of enzalutamide resistance in PCa, potentially offering a therapeutic avenue for enhancing the efficacy of enzalutamide to better manage this common malignancy.

Hypersecretion of glucagon from pancreatic α-cells strongly contributes to diabetic hyperglycemia. Moreover, failure of α-cells to increase glucagon secretion in response to falling blood glucose concentrations compromises the defense against hypoglycemia, a common complication in diabetes therapy. However, the mechanisms underlying glucose regulation of glucagon secretion are poorly understood and likely involve both α-cell–intrinsic and intraislet paracrine signaling. Among paracrine factors, glucose-stimulated release of the GABA metabolite γ-hydroxybutyric acid (GHB) from pancreatic β-cells might mediate glucose suppression of glucagon release via GHB receptors on α-cells. However, the direct effects of GHB on α-cell signaling and glucagon release have not been investigated. Here, we found that GHB (4–10 μm) lacked effects on the cytoplasmic concentrations of the secretion-regulating messengers Ca2+ and cAMP in mouse α-cells. Glucagon secretion from perifused mouse islets was also unaffected by GHB at both 1 and 7 mm glucose. The GHB receptor agonist 3-chloropropanoic acid and the antagonist NCS-382 had no effects on glucagon secretion and did not affect stimulation of secretion induced by a drop in glucose from 7 to 1 mm. Inhibition of endogenous GHB formation with the GABA transaminase inhibitor vigabatrin also failed to influence glucagon secretion at 1 mm glucose and did not prevent the suppressive effect of 7 mm glucose. In human islets, GHB tended to stimulate glucagon secretion at 1 mm glucose, an effect mimicked by 3-chloropropanoic acid. We conclude that GHB does not mediate the inhibitory effect of glucose on glucagon secretion.

Aldehyde oxidases (AOXs) are a small group of enzymes belonging to the larger family of molybdo-flavoenzymes, along with the well-characterized xanthine oxidoreductase. The two major types of reactions that are catalyzed by AOXs are the hydroxylation of heterocycles and the oxidation of aldehydes to their corresponding carboxylic acids. Different animal species have different complements of AOX genes. The two extremes are represented in humans and rodents; whereas the human genome contains a single active gene (AOX1), those of rodents, such as mice, are endowed with four genes (Aox1-4), clustering on the same chromosome, each encoding a functionally distinct AOX enzyme. It still remains enigmatic why some species have numerous AOX enzymes, whereas others harbor only one functional enzyme. At present, little is known about the physiological relevance of AOX enzymes in humans and their additional forms in other mammals. These enzymes are expressed in the liver and play an important role in the metabolisms of drugs and other xenobiotics. In this review, we discuss the expression, tissue-specific roles, and substrate specificities of the different mammalian AOX enzymes and highlight insights into their physiological roles.

The canonical pathway of eicosanoid production in most mammalian cells is initiated by phospholipase A2-mediated release of arachidonic acid, followed by its enzymatic oxidation resulting in a vast array of eicosanoid products. However, recent work has demonstrated that the major phospholipase in mitochondria, iPLA2γ (patatin-like phospholipase domain containing 8 (PNPLA8)), possesses sn-1 specificity, with polyunsaturated fatty acids at the sn-2 position generating polyunsaturated sn-2-acyl lysophospholipids. Through strategic chemical derivatization, chiral chromatographic separation, and multistage tandem MS, here we first demonstrate that human platelet-type 12-lipoxygenase (12-LOX) can directly catalyze the regioselective and stereospecific oxidation of 2-arachidonoyl-lysophosphatidylcholine (2-AA-LPC) and 2-arachidonoyl-lysophosphatidylethanolamine (2-AA-LPE). Next, we identified these two eicosanoid-lysophospholipids in murine myocardium and in isolated platelets. Moreover, we observed robust increases in 2-AA-LPC, 2-AA-LPE, and their downstream 12-LOX oxidation products, 12(S)-HETE-LPC and 12(S)-HETE-LPE, in calcium ionophore (A23187)-stimulated murine platelets. Mechanistically, genetic ablation of iPLA2γ markedly decreased the calcium-stimulated production of 2-AA-LPC, 2-AA-LPE, and 12-HETE-lysophospholipids in mouse platelets. Importantly, a potent and selective 12-LOX inhibitor, ML355, significantly inhibited the production of 12-HETE-LPC and 12-HETE-LPE in activated platelets. Furthermore, we found that aging is accompanied by significant changes in 12-HETE-LPC in murine serum that were also markedly attenuated by iPLA2γ genetic ablation. Collectively, these results identify previously unknown iPLA2γ-initiated signaling pathways mediated by direct 12-LOX oxidation of 2-AA-LPC and 2-AA-LPE. This oxidation generates previously unrecognized eicosanoid-lysophospholipids that may serve as biomarkers for age-related diseases and could potentially be used as targets in therapeutic interventions.

Heterotrimeric G proteins are the core upstream elements that transduce and amplify the cellular signals from G protein–coupled receptors (GPCRs) to intracellular effectors. GPCRs are the largest family of membrane proteins encoded in the human genome and are the targets of about one-third of prescription medicines. However, to date, no single therapeutic agent exerts its effects via perturbing heterotrimeric G protein function, despite a plethora of evidence linking G protein malfunction to human disease. Several recent studies have brought to light that the Gq family–specific inhibitor FR900359 (FR) is unexpectedly efficacious in silencing the signaling of Gq oncoproteins, mutant Gq variants that mostly exist in the active state. These data not only raise the hope that researchers working in drug discovery may be able to potentially strike Gq oncoproteins from the list of undruggable targets, but also raise questions as to how FR achieves its therapeutic effect. Here, we place emphasis on these recent studies and explain why they expand our pharmacological armamentarium for targeting Gq protein oncogenes as well as broaden our mechanistic understanding of Gq protein oncogene function. We also highlight how this novel insight impacts the significance and utility of using G(q) proteins as targets in drug discovery efforts.

Heme-regulatory motifs (HRMs) are present in many proteins that are involved in diverse biological functions. The C-terminal tail region of human heme oxygenase-2 (HO2) contains two HRMs whose cysteine residues form a disulfide bond; when reduced, these cysteines are available to bind Fe3+-heme. Heme binding to the HRMs occurs independently of the HO2 catalytic active site in the core of the protein, where heme binds with high affinity and is degraded to biliverdin. Here, we describe the reversible, protein-mediated transfer of heme between the HRMs and the HO2 core. Using hydrogen-deuterium exchange (HDX)-MS to monitor the dynamics of HO2 with and without Fe3+-heme bound to the HRMs and to the core, we detected conformational changes in the catalytic core only in one state of the catalytic cycle—when Fe3+-heme is bound to the HRMs and the core is in the apo state. These conformational changes were consistent with transfer of heme between binding sites. Indeed, we observed that HRM-bound Fe3+-heme is transferred to the apo-core either upon independent expression of the core and of a construct spanning the HRM-containing tail or after a single turnover of heme at the core. Moreover, we observed transfer of heme from the core to the HRMs and equilibration of heme between the core and HRMs. We therefore propose an Fe3+-heme transfer model in which HRM-bound heme is readily transferred to the catalytic site for degradation to facilitate turnover but can also equilibrate between the sites to maintain heme homeostasis.

In cyanobacteria, metabolic pathways that use the nitrogen-rich amino acid arginine play a pivotal role in nitrogen storage and mobilization. The N-terminal domains of two recently identified bacterial enzymes: ArgZ from Synechocystis and AgrE from Anabaena, have been found to contain an arginine dihydrolase. This enzyme provides catabolic activity that converts arginine to ornithine, resulting in concomitant release of CO2 and ammonia. In Synechocystis, the ArgZ-mediated ornithine–ammonia cycle plays a central role in nitrogen storage and remobilization. The C-terminal domain of AgrE contains an ornithine cyclodeaminase responsible for the formation of proline from ornithine and ammonia production, indicating that AgrE is a bifunctional enzyme catalyzing two sequential reactions in arginine catabolism. Here, the crystal structures of AgrE in three different ligation states revealed that it has a tetrameric conformation, possesses a binding site for the arginine dihydrolase substrate l-arginine and product l-ornithine, and contains a binding site for the coenzyme NAD(H) required for ornithine cyclodeaminase activity. Structure–function analyses indicated that the structure and catalytic mechanism of arginine dihydrolase in AgrE are highly homologous with those of a known bacterial arginine hydrolase. We found that in addition to other active-site residues, Asn-71 is essential for AgrE's dihydrolase activity. Further analysis suggested the presence of a passage for substrate channeling between the two distinct AgrE active sites, which are situated ∼45 Å apart. These results provide structural and functional insights into the bifunctional arginine dihydrolase–ornithine cyclodeaminase enzyme AgrE required for arginine catabolism in Anabaena.

Treatment of patients with chronic lymphocytic leukemia (CLL) with inhibitors of Bruton's tyrosine kinase (BTK), such as ibrutinib, is limited by primary or secondary resistance to this drug. Examinations of CLL patients with late relapses while on ibrutinib, which inhibits BTK's catalytic activity, revealed several mutations in BTK, most frequently resulting in the C481S substitution, and disclosed many mutations in PLCG2, encoding phospholipase C-γ2 (PLCγ2). The PLCγ2 variants typically do not exhibit constitutive activity in cell-free systems, leading to the suggestion that in intact cells they are hypersensitive to Rac family small GTPases or to the upstream kinases spleen-associated tyrosine kinase (SYK) and Lck/Yes-related novel tyrosine kinase (LYN). The sensitivity of the PLCγ2 variants to BTK itself has remained unknown. Here, using genetically-modified DT40 B lymphocytes, along with various biochemical assays, including analysis of PLCγ2-mediated inositol phosphate formation, inositol phospholipid assessments, fluorescence recovery after photobleaching (FRAP) static laser microscopy, and determination of intracellular calcium ([Ca2+]i), we show that various CLL-specific PLCγ2 variants such as PLCγ2S707Y are hyper-responsive to activated BTK, even in the absence of BTK's catalytic activity and independently of enhanced PLCγ2 phospholipid substrate supply. At high levels of B-cell receptor (BCR) activation, which may occur in individual CLL patients, catalytically-inactive BTK restored the ability of the BCR to mediate increases in [Ca2+]i. Because catalytically-inactive BTK is insensitive to active-site BTK inhibitors, the mechanism involving the noncatalytic BTK uncovered here may contribute to preexisting reduced sensitivity or even primary resistance of CLL to these drugs.

The protein-tyrosine phosphatase SHP2 is an allosteric enzyme critical for cellular events downstream of growth factor receptors. Mutations in the SHP2 gene have been linked to many different types of human diseases, including developmental disorders, leukemia, and solid tumors. Unlike most SHP2-activating mutations, the T507K substitution in SHP2 is unique in that it exhibits oncogenic Ras-like transforming activity. However, the biochemical basis of how the SHP2/T507K variant elicits transformation remains unclear. By combining kinetic and biophysical methods, X-ray crystallography, and molecular modeling, as well as using cell biology approaches, here we uncovered that the T507K substitution alters both SHP2 substrate specificity and its allosteric regulatory mechanism. We found that although SHP2/T507K exists in the closed, autoinhibited conformation similar to the WT enzyme, the interactions between its N-SH2 and protein-tyrosine phosphatase domains are weakened such that SHP2/T507K possesses a higher affinity for the scaffolding protein Grb2-associated binding protein 1 (Gab1). We also discovered that the T507K substitution alters the structure of the SHP2 active site, resulting in a change in SHP2 substrate preference for Sprouty1, a known negative regulator of Ras signaling and a potential tumor suppressor. Our results suggest that SHP2/T507K's shift in substrate specificity coupled with its preferential association of SHP2/T507K with Gab1 enable the mutant SHP2 to more efficiently dephosphorylate Sprouty1 at pTyr-53. This dephosphorylation hyperactivates Ras signaling, which is likely responsible for SHP2/T507K's Ras-like transforming activity.

Pathogenic bacteria of the genera Mycobacterium and Corynebacterium cause severe human diseases such as tuberculosis (Mycobacterium tuberculosis) and diphtheria (Corynebacterium diphtheriae). The cells of these species are surrounded by protective cell walls rich in long-chain mycolic acids. These fatty acids are conjugated to the disaccharide trehalose on the cytoplasmic side of the bacterial cell membrane. They are then transported across the membrane to the periplasm where they act as donors for other reactions. We have previously shown that transient acetylation of the glycolipid trehalose monohydroxycorynomycolate (hTMCM) enables its efficient transport to the periplasm in Corynebacterium glutamicum and that acetylation is mediated by the membrane protein TmaT. Here, we show that a putative methyltransferase, encoded at the same genetic locus as TmaT, is also required for optimal hTMCM transport. Deletion of the C. glutamicum gene NCgl2764 (Rv0224c in M. tuberculosis) abolished acetyltrehalose monocorynomycolate (AcTMCM) synthesis, leading to accumulation of hTMCM in the inner membrane and delaying its conversion to trehalose dihydroxycorynomycolate (h2TDCM). Complementation with NCgl2764 normalized turnover of hTMCM to h2TDCM. In contrast, complementation with NCgl2764 derivatives mutated at residues essential for methyltransferase activity failed to rectify the defect, suggesting that NCgl2764/Rv0224c encodes a methyltransferase, designated here as MtrP. Comprehensive analyses of the individual mtrP and tmaT mutants and of a double mutant revealed strikingly similar changes across several lipid classes compared with WT bacteria. These findings indicate that both MtrP and TmaT have nonredundant roles in regulating AcTMCM synthesis, revealing additional complexity in the regulation of trehalose mycolate transport in the Corynebacterineae.

Extracellular matrix-evoked angiostasis and autophagy within the tumor microenvironment represent two critical, but unconnected, functions of the small leucine-rich proteoglycan, decorin. Acting as a partial agonist of vascular endothelial growth factor 2 (VEGFR2), soluble decorin signals via the energy sensing protein, AMP-activated protein kinase (AMPK), in the autophagic degradation of intracellular vascular endothelial growth factor A (VEGFA). Here, we discovered that soluble decorin evokes intracellular catabolism of endothelial VEGFA that is mechanistically independent of mTOR, but requires an autophagic regulator, paternally expressed gene 3 (PEG3). We found that administration of autophagic inhibitors such as chloroquine or bafilomycin A1, or depletion of autophagy-related 5 (ATG5), results in accumulation of intracellular VEGFA, indicating that VEGFA is a basal autophagic substrate. Mechanistically, decorin increased the VEGFA clearance rate by augmenting autophagic flux, a process that required RAB24 member RAS oncogene family (RAB24), a small GTPase that facilitates the disposal of autophagic compartments. We validated these findings by demonstrating the physiological relevance of this process in vivo. Mice starved for 48 h exhibited a sharp decrease in overall cardiac and aortic VEGFA that could be blocked by systemic chloroquine treatment. Thus, our findings reveal a unified mechanism for the metabolic control of endothelial VEGFA for autophagic clearance in response to decorin and canonical pro-autophagic stimuli. We posit that the VEGFR2/AMPK/PEG3 axis integrates the anti-angiogenic and pro-autophagic bioactivities of decorin as the molecular basis for tumorigenic suppression. These results support future therapeutic use of decorin as a next-generation protein therapy to combat cancer.