Carla Farsi, Laura Scull and Jordan Watts
Proc. Amer. Math. Soc. 148 (2020), 2717-2737.
Abstract, references and article information

Weimin Chen
Proc. Amer. Math. Soc. 148 (2020), 2707-2716.
Abstract, references and article information

Mahmoud Benkhalifa
Proc. Amer. Math. Soc. 148 (2020), 2695-2706.
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

Daniel Carando, Santiago Muro and Daniela M. Vieira
Proc. Amer. Math. Soc. 148 (2020), 2447-2457.
Abstract, references and article information

Claude Cibils, Marcelo Lanzilotta, Eduardo N. Marcos and Andrea Solotar
Proc. Amer. Math. Soc. 148 (2020), 2421-2432.
Abstract, references and article information

Naoya Hiramatsu and Ryo Takahashi
Proc. Amer. Math. Soc. 148 (2020), 2359-2369.
Abstract, references and article information

Joseph Reid
Proc. Amer. Math. Soc. 148 (2020), 2331-2343.
Abstract, references and article information

A total of 27 Hong Kong residents who left Morocco on a chartered flight arranged by the Chinese Embassy in the Kingdom of Morocco arrived in Guangzhou today.

Among them, 26 people subsequently took the coaches arranged by the Hong Kong Special Administrative Region Government to return to Hong Kong through the Shenzhen Bay Port and have arrived at AsiaWorld-Expo.

One Hong Kong resident chose to stay in Guangzhou for a 14-day isolation period for medical surveillance in accordance with the relevant requirements.

Hong Kong has, for the first time, held the Willem C Vis (East) International Commercial Arbitration Moot (VEM) through an online platform amidst the COVID-19 pandemic. While most of the competitions in other jurisdictions have been cancelled or postponed due to challenges posed by the pandemic, the 17th VEM was the only international mooting which went ahead as scheduled through an online dispute resolution (ODR) platform.

Though the outbreak of COVID-19 has changed our travel patterns and presented many challenges, advance in modern technology has helped us to address them. For the first time in the moot’s history, the mooting competition was conducted completely online with the support of Electronic Business Related Arbitration & Mediation (eBRAM). The platform supported by eBRAM accommodated 71 teams from 21 jurisdictions and about 250 arbitrators from 52 jurisdictions to take part in the moot which started on March 22. This exemplifies the importance of technological developments in the legal field.

The audience, with the latest lawtech support by eBRAM, watched the lively and intensive oral arguments online with participants of the finalists showing considerable flair and aptitude in trying their best to present their case to an international panel of distinguished arbitrators. The Chinese University of Hong Kong won the competition after rounds of rigorous and remarkable oral submissions before the panel.

The Government has always been supportive of the development of lawtech spearheaded by, amongst others, eBRAM, which is expected to be launched this year to resolve cross-boundary disputes online. If funding is approved by the Legislative Council Finance Committee on time, eBRAM would be able to provide an efficient, cost-effective and safe online platform for deal-making and resolution of cross-boundary commercial and investment disputes. We understand that eBRAM also plans to develop an online dispute resolution platform to support cross-boundary business-to-business transactions in the Asia-Pacific Economic Cooperation region.

We would continue to offer our support to the VEM as part of our legal education campaign. However, the VEM would not have been held smoothly without the technical support provided by eBRAM and also the tenacity and determination displayed by the Vis East Moot Foundation. The successful conclusion of the moot proved that Hong Kong has the capability of developing lawtech.

Changes are inevitable, including technological changes. The COVID-19 pandemic posed new challenges to Hong Kong, but it also provides an opportunity for us to explore lawtech in the provision of legal services. We all should join hands to make the best use of the technologies to develop ODR to assist all parties in resolving disputes in an efficient, effective and fair manner with a view to bringing rule of law and justice for all.

Secretary for Justice Teresa Cheng wrote this article and posted it on her blog on March 31.

Banks and financial institutions taking part in providing mortgage loans for the Housing Authority Subsidised Sale Flats Scheme (SSFS) may offer a mortgage principal moratorium plan to the scheme’s mortgagors.

The authority today wrote to these institutions to confirm and agree that such a plan is applicable for SSFS flats.

Principal repayment may be deferred for a maximum 12-month period and the mortgage loan repayment period may be extended correspondingly by a maximum of 12 months.

The principal moratorium period may commence by December 31 this year at the latest.

The arrangement is applicable to the Home Ownership Scheme, the Private Sector Participation Scheme, the Buy or Rent Option Scheme, the Tenants Purchase Scheme and the Green Form Subsidised Home Ownership Scheme in the primary market and under the Secondary Market Scheme.

To encourage participating financial institutions to provide mortgage loans and better mortgage terms for SSFS flat purchasers, the authority provides a mortgage default guarantee for them.

It undertakes to meet the shortfall in repayment in the event of default by the borrowers under specified circumstances during the guarantee period.

Due to the requirements in the guarantee deed on the mortgage loan period and the monthly instalment amount, participating financial institutions may not be able to offer a mortgage principal moratorium plan to SSFS flat owners.

In light of the economic downturn arising from the COVID-19 outbreak, the authority confirmed today that a mortgage principal moratorium plan is applicable for SSFS flats.

The move will encourage participating financial institutions to offer such a plan to SSFS flat owners, reducing their burden of mortgage repayment.

The tender for a Mong Kok site has been awarded on a 50-year land grant at a premium of $467.18 million, the Lands Department announced today.

Kowloon Inland Lot No. 11240 at the junction of Soy Street and Shanghai Street was awarded to Worth Forever, a subsidiary of Bring Bright.

It has a site area of about 625.5 sq m with a minimum gross floor area of 3,751.75 sq m.

The maximum gross floor area for private residential purposes is 4,691.25 sq m.

The maximum gross floor area for non-industrial purposes is computed according to the relevant special condition in the conditions of sale.

The Education Bureau today issued a circular memorandum to tutorial schools, inviting them to apply for a relief grant under the Anti-epidemic Fund.

The bureau said a total of about $120 million has been allocated from the fund to provide a one-off relief grant of $40,000 to each eligible tutorial school.

These tutorial schools must be registered under the Education Ordinance, have been operating in the three months before the class suspension - November, December and January - and be in operation on the application date.

Designated centres under the Financial Assistance Scheme for Designated Evening Adult Education Courses, which offer evening secondary school courses for adult learners, are also eligible for the grant.

The measure is expected to benefit about 3,000 tutorial schools, and the relief grant will be disbursed about four weeks upon receipt of an application.

Additionally, the fund will also provide relief grants to school-related service providers who have been affected by the prolonged class suspension, incurring an expenditure of about $419 million.

Beneficiaries will include operators of catering outlets at primary schools, secondary schools and post-secondary institutions and lunchbox providers of primary and secondary schools.

School bus drivers, school private light bus drivers and escorts, or nannies, as well as instructors, coaches, trainers and operators of interest classes engaged by schools, will also benefit from the relief grants.

The bureau will distribute application forms for the relief grant through post-secondary institutions to the catering outlets operating on their campuses within this week. The application details for other relief grants will be announced as soon as possible.

Separately, the bureau announced earlier that it would provide a one-off relief grant of $80,000 to each private school offering full and formal curriculum.

The grant has been disbursed progressively to schools under the English Schools Foundation, international schools, private independent schools, and other private secondary day schools and private primary schools.

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

Shani V. Davis
Aug 1, 2011; 24:148-153
Feature Article/Vitamin D in African Americans

Peggy Yarborough
Jan 1, 2003; 16:
Case Studies

Curtis Triplitt
Oct 1, 2006; 19:202-211
Pharmacy Update

Guillermo E. Umpierrez
Jan 1, 2002; 15:
Articles

Geralyn Spollett
Jan 1, 2003; 16:
Case Studies

The Mortgage Corporation today announced that the pilot scheme for fixed-rate mortgages will start receiving applications from May 7.

The aggregate loan amount of the Fixed-rate Mortgage Pilot Scheme is $1 billion, subject to a maximum loan amount of each private residential mortgage of $10 million.

Financial Secretary Paul Chan said the pilot scheme, announced in the 2020-21 Budget, provides an alternative financing option to homebuyers for mitigating their risks arising from interest rate volatility, thereby promoting the development of the mortgage market in the long run.

In response to the change in market interest rates, mortgage interest rates under the pilot scheme have been lowered, as compared to the levels previously announced in the Budget. The interest rates per annum for 10, 15 and 20 years are 2.55%, 2.65% and 2.75%.

Mortgages under the pilot scheme will be offered through Bank of China, Chong Hing Bank, Dah Sing Bank, Industrial & Commercial Bank of China, Shanghai Commercial Bank, Standard Chartered Bank and The Bank of East Asia.

At the end of the fixed-rate period, borrowers may either re-fix the mortgage rate under fixed-rate mortgages or convert the mortgage to a loan on a floating rate, which is the prime rate minus 2.35%.

The pilot scheme will be effective until October 31.

To align with the phased resumption of public services, the Information Services Department, Government Records Service and Civil Aviation Department have announced their latest arrangements.

The Information Services Department will resume sales counter services at its Publications Sales Unit and Photo Library at North Point Government Offices from May 4.

The sales office will be open from 9am to 12.30pm and from 2pm to 6pm from Monday to Friday.

To reduce social contact and avoid people gathering, citizens are encouraged to purchase government publications and photos through the online bookstore and photo store.

The Government Records Service's Public Records Office will provide search room services, including onsite loan and circulation services, from Monday to Friday, 9am to 5.45pm, for people who have made reservations through the online catalogue.

The office will also resume search room services from 9am to 1pm on Saturdays for people to inspect holdings which have been reserved online. 

Requests by up to 15 users will be accepted for search room services for each open day on a first-come, first-served basis. Users will be notified of the reservation results by email.

Visitor and public education programmes will continue to be suspended, while the Exhibition Hall at the Public Records Building will be temporarily closed for preparation of the new thematic exhibition until further notice.

Enquiries can be made to 2195 7700 or via email.

The Civil Aviation Department’s Personnel Licensing Office will continue to provide counter services from next Monday and resume relevant licensing examinations.

The office's opening hours are 8.45am to 12.45pm and 1.45pm to 5pm, Monday to Friday. Enquiries can be made to 2910 6046 or via email.

Click here for the latest public service arrangements.

All the details on Uber's biggest announcements as well as updates on the controversial company's trials and tribulations

The digital challenger bank is now the most switched to bank in the UK as Nationwide Building Society loses its long-held top spot

The Housing Authority’s Commercial Properties Committee today approved the extension of rent concessions to over 8,300 non-domestic tenants or licensees for six months from April 1 to September 30.

The authority had earlier granted a 50% rent concession to its eligible retail and factory tenants for six months from April 1.

Under the extension, their rent concession will be increased to 75% over the same period with retrospective effect from April 1. The rent concession does not include rates and air-conditioning charges.

The authority said such further measures are to support the Government's new series of measures announced in early April to relieve the financial burden of individuals and businesses.

A total of 2,450 retail and 3,300 factory tenants will benefit from the approved increase in the rent concession.

The 75% rent concession will also be extended to cover tenants and licensees of bus kiosks and most advertising signboards, as well as car park users for the monthly parking of commercial vehicles.

About 40 tenancies for bus kiosks, 80 advertising signboards and about 2,500 car park users stand to benefit from the concession.

Tenants of premises in the authority's properties which are required to be closed under relevant regulations or the Government's directions, may also apply to the authority for a 100% rent concession for the period during which they are required to be closed.

The authority added that the approved measures will be implemented as soon as possible. For rent and licence fees already paid for the months of April and May, arrangements will be made for offsetting in the payment for subsequent months.

The committee has approved three rounds of rent concessions since last September. Together with this round, the total rent and licence fees foregone by the authority is estimated to reach more than $1 billion.

Below, Mac Hyman, Tulane University, talks about types of mathematical models--their strengths and weaknesses--the data that we currently have and what we really need, and what models can tell us about a possible second wave.

At the beginning of the video, he thanks the mathematics community for its work, and near the end says, "Our mathematical community is really playing a central role in helping to predict the spread, and help mitigate this epidemic, and prioritize our efforts. …Do not underestimate the power that mathematics can have in helping to mitigate this epidemic—-we have a role to play."

See the full set of videos on modeling COVID-19 and see media coverage of mathematics' role in modeling the pandemic.

(Rice University) Rice University researchers have integrated high-efficiency solar cells and electrode catalysts into an efficient, low-cost device that splits water to produce hydrogen fuel.

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

Claus Sorensen
Represent. Theory 24 (2020), 151-177.
Abstract, references and article information

"Artist uses snow as canvas for massive geometrical designs," by Thomas Peipert, AP, January 16, 2020.

Neoantimycins are anticancer compounds of 15-membered ring antimycin-type depsipeptides. They are biosynthesized by a hybrid multimodular protein complex of nonribosomal peptide synthetase (NRPS) and polyketide synthase (PKS), typically from the starting precursor 3-formamidosalicylate. Examining fermentation extracts of Streptomyces conglobatus, here we discovered four new neoantimycin analogs, unantimycins B–E, in which 3-formamidosalicylates are replaced by an unusual 3-hydroxybenzoate (3-HBA) moiety. Unantimycins B–E exhibited levels of anticancer activities similar to those of the chemotherapeutic drug cisplatin in human lung cancer, colorectal cancer, and melanoma cells. Notably, they mostly displayed no significant toxicity toward noncancerous cells, unlike the serious toxicities generally reported for antimycin-type natural products. Using site-directed mutagenesis and heterologous expression, we found that unantimycin productions are correlated with the activity of a chorismatase homolog, the nat-hyg5 gene, from a type I PKS gene cluster. Biochemical analysis confirmed that the catalytic activity of Nat-hyg5 generates 3-HBA from chorismate. Finally, we achieved selective production of unantimycins B and C by engineering a chassis host. On the basis of these findings, we propose that unantimycin biosynthesis is directed by the neoantimycin-producing NRPS–PKS complex and initiated with the starter unit of 3-HBA. The elucidation of the biosynthetic unantimycin pathway reported here paves the way to improve the yield of these compounds for evaluation in oncotherapeutic applications.

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.

Myostatin (or growth/differentiation factor 8 (GDF8)) is a member of the transforming growth factor β superfamily of growth factors and negatively regulates skeletal muscle growth. Its dysregulation is implicated in muscle wasting diseases. SRK-015 is a clinical-stage mAb that prevents extracellular proteolytic activation of pro- and latent myostatin. Here we used integrated structural and biochemical approaches to elucidate the molecular mechanism of antibody-mediated neutralization of pro-myostatin activation. The crystal structure of pro-myostatin in complex with 29H4-16 Fab, a high-affinity variant of SRK-015, at 2.79 Å resolution revealed that the antibody binds to a conformational epitope in the arm region of the prodomain distant from the proteolytic cleavage sites. This epitope is highly sequence-divergent, having only limited similarity to other closely related members of the transforming growth factor β superfamily. Hydrogen/deuterium exchange MS experiments indicated that antibody binding induces conformational changes in pro- and latent myostatin that span the arm region, the loops contiguous to the protease cleavage sites, and the latency-associated structural elements. Moreover, negative-stain EM with full-length antibodies disclosed a stable, ring-like antigen–antibody structure in which the two Fab arms of a single antibody occupy the two arm regions of the prodomain in the pro- and latent myostatin homodimers, suggesting a 1:1 (antibody:myostatin homodimer) binding stoichiometry. These results suggest that SRK-015 binding stabilizes the latent conformation and limits the accessibility of protease cleavage sites within the prodomain. These findings shed light on approaches that specifically block the extracellular activation of growth factors by targeting their precursor forms.

Pyruvate kinase muscle isoform 2 (PKM2) is a key glycolytic enzyme involved in ATP generation and critical for cancer metabolism. PKM2 is expressed in many human cancers and is regulated by complex mechanisms that promote tumor growth and proliferation. Therefore, it is considered an attractive therapeutic target for modulating tumor metabolism. Various stimuli allosterically regulate PKM2 by cycling it between highly active and less active states. Several small molecules activate PKM2 by binding to its intersubunit interface. Serine and cysteine serve as an activator and inhibitor of PKM2, respectively, by binding to its amino acid (AA)-binding pocket, which therefore represents a potential druggable site. Despite binding similarly to PKM2, how cysteine and serine differentially regulate this enzyme remains elusive. Using kinetic analyses, fluorescence binding, X-ray crystallography, and gel filtration experiments with asparagine, aspartate, and valine as PKM2 ligands, we examined whether the differences in the side-chain polarity of these AAs trigger distinct allosteric responses in PKM2. We found that Asn (polar) and Asp (charged) activate PKM2 and that Val (hydrophobic) inhibits it. The results also indicate that both Asn and Asp can restore the activity of Val-inhibited PKM2. AA-bound crystal structures of PKM2 displayed distinctive interactions within the binding pocket, causing unique allosteric effects in the enzyme. These structure-function analyses of AA-mediated PKM2 regulation shed light on the chemical requirements in the development of mechanism-based small-molecule modulators targeting the AA-binding pocket of PKM2 and provide broader insights into the regulatory mechanisms of complex allosteric enzymes.

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.

β-1,3-d-Glucan is a ubiquitous glucose polymer produced by plants, bacteria, and most fungi. It has been used as a diagnostic tool in patients with invasive mycoses via a highly-sensitive reagent consisting of the blood coagulation system of horseshoe crab. However, no method is currently available for measuring β-1,6-glucan, another primary β-glucan structure of fungal polysaccharides. Herein, we describe the development of an economical and highly-sensitive and specific assay for β-1,6-glucan using a modified recombinant endo-β-1,6-glucanase having diminished glucan hydrolase activity. The purified β-1,6-glucanase derivative bound to the β-1,6-glucan pustulan with a KD of 16.4 nm. We validated the specificity of this β-1,6-glucan probe by demonstrating its ability to detect cell wall β-1,6-glucan from both yeast and hyphal forms of the opportunistic fungal pathogen Candida albicans, without any detectable binding to glucan lacking the long β-1,6-glucan branch. We developed a sandwich ELISA-like assay with a low limit of quantification for pustulan (1.5 pg/ml), and we successfully employed this assay in the quantification of extracellular β-1,6-glucan released by >250 patient-derived strains of different Candida species (including Candida auris) in culture supernatant in vitro. We also used this assay to measure β-1,6-glucan in vivo in the serum and in several organs in a mouse model of systemic candidiasis. Our work describes a reliable method for β-1,6-glucan detection, which may prove useful for the diagnosis of invasive fungal infections.

The actin cytoskeleton is extremely dynamic and supports diverse cellular functions in many physiological and pathological processes, including tumorigenesis. However, the mechanisms that regulate the actin-related protein 2/3 (ARP2/3) complex and thereby promote actin polymerization and organization in cancer cells are not well-understood. We previously implicated the proline-rich 11 (PRR11) protein in lung cancer development. In this study, using immunofluorescence staining, actin polymerization assays, and siRNA-mediated gene silencing, we uncovered that cytoplasmic PRR11 is involved in F-actin polymerization and organization. We found that dysregulation of PRR11 expression results in F-actin rearrangement and nuclear instability in non-small cell lung cancer cells. Results from molecular mechanistic experiments indicated that PRR11 associates with and recruits the ARP2/3 complex, facilitates F-actin polymerization, and thereby disrupts the F-actin cytoskeleton, leading to abnormal nuclear lamina assembly and chromatin reorganization. Inhibition of the ARP2/3 complex activity abolished irregular F-actin polymerization, lamina assembly, and chromatin reorganization due to PRR11 overexpression. Notably, experiments with truncated PRR11 variants revealed that PRR11 regulates F-actin through different regions. We found that deletion of either the N or C terminus of PRR11 abrogates its effects on F-actin polymerization and nuclear instability and that deletion of amino acid residues 100–184 or 100–200 strongly induces an F-actin structure called the actin comet tail, not observed with WT PRR11. Our findings indicate that cytoplasmic PRR11 plays an essential role in regulating F-actin assembly and nuclear stability by recruiting the ARP2/3 complex in human non-small cell lung carcinoma cells.

Lethal infections by strains of the highly-pathogenic avian influenza virus (HPAIV) H5N1 pose serious threats to both the poultry industry and public health worldwide. A lack of confirmed HPAIV epitopes recognized by cytotoxic T lymphocytes (CTLs) has hindered the utilization of CD8+ T-cell–mediated immunity and has precluded the development of effectively diversified epitope-based vaccination approaches. In particular, an HPAIV H5N1 CTL-recognized epitope based on the peptide MHC-I–β2m (pMHC-I) complex has not yet been designed. Here, screening a collection of selected peptides of several HPAIV strains against a specific pathogen-free pMHC-I (pBF2*1501), we identified a highly-conserved HPAIV H5N1 CTL epitope, named HPAIV–PA123–130. We determined the structure of the BF2*1501–PA123–130 complex at 2.1 Å resolution to elucidate the molecular mechanisms of a preferential presentation of the highly-conserved PA123–130 epitope in the chicken B15 lineage. Conformational characteristics of the PA123–130 epitope with a protruding Tyr-7 residue indicated that this epitope has great potential to be recognized by specific TCRs. Moreover, significantly increased numbers of CD8+ T cells specific for the HPAIV–PA123–130 epitope in peptide-immunized chickens indicated that a repertoire of CD8+ T cells can specifically respond to this epitope. We anticipate that the identification and structural characterization of the PA123–130 epitope reported here could enable further studies of CTL immunity against HPAIV H5N1. Such studies may aid in the development of vaccine development strategies using well-conserved internal viral antigens in chickens.

The linear ubiquitin assembly complex (LUBAC) is an essential component of the innate and adaptive immune system. Modification of cellular substrates with linear polyubiquitin chains is a key regulatory step in signal transduction that impacts cell death and inflammatory signaling downstream of various innate immunity receptors. Loss-of-function mutations in the LUBAC components HOIP and HOIL-1 yield a systemic autoinflammatory disease in humans, whereas their genetic ablation is embryonically lethal in mice. Deficiency of the LUBAC adaptor protein Sharpin results in a multi-organ inflammatory disease in mice characterized by chronic proliferative dermatitis (cpdm), which is propagated by TNFR1-induced and RIPK1-mediated keratinocyte cell death. We have previously shown that caspase-1 and -11 promoted the dermatitis pathology of cpdm mice and mediated cell death in the skin. Here, we describe a reciprocal regulation of caspase-1 and LUBAC activities in keratinocytes. We show that LUBAC interacted with caspase-1 via HOIP and modified its CARD domain with linear polyubiquitin and that depletion of HOIP or Sharpin resulted in heightened caspase-1 activation and cell death in response to inflammasome activation, unlike what is observed in macrophages. Reciprocally, caspase-1, as well as caspase-8, regulated LUBAC activity by proteolytically processing HOIP at Asp-348 and Asp-387 during the execution of cell death. HOIP processing impeded substrate ubiquitination in the NF-κB pathway and resulted in enhanced apoptosis. These results highlight a regulatory mechanism underlying efficient apoptosis in keratinocytes and provide further evidence of a cross-talk between inflammatory and cell death pathways.

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.

VOLUME 295 (2020) PAGES 3285–3300An incorrect graph was used in Fig. 5C. This error has now been corrected. Additionally, some of the statistics reported in the legend and text referring to Fig. 5C were incorrect. The F statistics for Fig. 5C should state Fken(3,16) = 7.454, p < 0.01; FCCCP(1,16) = 102.9, p < 0.0001; Finteraction(3,16) = 7.480, p < 0.01. This correction does not affect the results or conclusions of this work.jbc;295/17/5835/F5F1F5Figure 5C.