The London-headquartered fintech startup Soldo has repurposed its spend management tools for local authorities in Italy to support its COVID-19 emergency response measures

A. G. Kukush and O. O. Chernova
Theor. Probability and Math. Statist. 99 (2020), 125-135.
Abstract, references and article information

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

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...

The COVID-19 pandemic has impacted business activity and supply chains across the globe, with numerous trade fairs and events around the world being postponed or cancelled, depriving many enterprises of business and marketing...

As we all know, Hong Kong as well as most parts of the world are facing a pandemic that has an enormous negative impact on our social and economic life. At this juncture, we don't have any accurate way to predict what will happen in the coming months. Two months ago, we were worried about whether COVID-19 would become a pandemic. Yet, the scale of the pandemic as we see now is not what we could have imagined two months ago. What we can do now is tackle the social and economic crisis upfront and build the resilience of our society, in particular, our employment market, so that when the time comes where social and economic activities can resume no matter how gradually or rapidly, our society can bounce back as soon as possible.

Unemployment has edged up bit by bit since the latter part of 2019. Statistics and daily news about business closures are telling us that unemployment is going up rapidly. While we should see what can be done to help those unemployed, the more important and urgent task is to see how we can "stop the bleeding", which essentially means job retention. The Employment Support Scheme, with a budget of over $80 billion, is designed exactly for that purpose. Through providing time-limited financial support, the whole idea of this scheme is to preserve jobs by enabling employers to keep their employees in employment for the coming months, and also when business resumes, employers can immediately grab the opportunities.

The central idea of the Employment Support Scheme is to provide wage subsidy that is equivalent to 50% of the wages of the employees up to a wage cap of $18,000 per month. The subsidy is given to the employers so that they can keep their staff for the coming six months. The employers will be required to have no redundancy or layoffs during the months that they receive wage subsidies from the Government.

In Hong Kong, we do not have a pay-as-you-go income tax system. Neither do we have a social insurance system nor a central provident fund to cover everyone in our workforce. That means we do not have any existing system covering every employer and employee in Hong Kong that we can devise a wage subsidy scheme that covers everyone. Any system meant to cover everyone in our workforce must be mandatory in nature and that will take time for us to have the relevant legislation in place and subsequently the system built.

However, schemes under the Mandatory Provident Fund (MPF) and the other Occupational Retirement Schemes provide a framework that we can develop a wage subsidy scheme to cover the great majority of the workforce. This is definitely not sufficient. In particular, we have identified three sectors that do not have good coverage in the provident fund systems. They are the catering industry, the construction industry and the passenger transport sector. Under the Anti-epidemic Fund, we have three sector-specific schemes to assist the employers and the employees in these sectors.

Many freelance workers or those in the so-called slash economy do not make contributions to the MPF. Though we have over 200,000 self-employed persons having an account in the MPF system, they do not pay MPF regularly. While we will provide a one-off wage subsidy to those self-employed persons who have made MPF contributions within the past 15 months, we also have three separate but mutually exclusive schemes operating under the Home Affairs Bureau, the Education Bureau and the Social Welfare Department, providing the same one-off wage subsidy to those freelance workers who provide arts and sports training. The one-off wage subsidy is $7,500.

Though all the schemes I mentioned above still cannot cover everyone in the workforce, this is the best we can do in making use of existing systems so that we can launch this round of the Anti-epidemic Fund in the shortest possible time to help our employers and employees to survive the challenges that are with us now. Any new systems to be built from scratch will not be able to provide the necessary timely support that employers and employees desperately need.

As mentioned earlier, unemployment is increasing at a disturbing rate. The basic unemployment protection system in Hong Kong relies on two legs. One is the Severance Payment or Long Service Payment payable by the employers, which is equivalent to two-thirds of the monthly salary times the number of years of service with the employer. The other is the Comprehensive Social Security Assistance (CSSA) Scheme. The CSSA provides a level of income support to families for their basic level of living in the context of Hong Kong. The CSSA provides a safety net to any family not having sufficient means, including those who are unemployed.

Apart from the income test, the CSSA also has an asset test. For the purpose of providing extra help to those unemployed during this difficult time, the Government will double the existing asset limit for the able-bodied for a limited period of six months, allowing more families with people unemployed to become eligible to receive CSSA. We estimated that about 40,000 families will benefit from this enhancement.

Unfortunately, over the years there is a social stigma towards the CSSA system. People in desperation may be deterred from applying for CSSA simply because of the stigma. This is the time for us to destigmatise the CSSA system. It is the safety net for citizens of Hong Kong. It is the responsibility of an affluent society like Hong Kong to provide the basic level of living to those who cannot afford to do so on their own. This is the time, this difficult time, that this safety net should perform its basic function.

We are doing our best to support Hong Kong in this epidemic fight. Let's weather the storm and brave the challenges together.

This is the Letter to Hong Kong by Secretary for Labour & Welfare Dr Law Chi-kwong on anti-epidemic measures and the Employment Support Scheme carried on Radio Television Hong Kong Radio 3 on April 19.

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.

Recipients of the Individual-based Work Incentive Transport Subsidy (I-WITS) will receive a one-off extra allowance after the passage of the Appropriation Bill 2020, the Government announced today.

The extra allowance was proposed in the 2020-21 Budget and would be disbursed one month after the bill’s passage at the earliest.

Eligible recipients are those whose I-WITS applications were made in the applicable period - from the first day of the month in which the bill is passed to the date of the bill’s passage, and six calendar months before that month.

New applicants or previous I-WITS recipients who have yet to submit applications in the applicable period should do so on or before the date of the bill’s passage to be eligible for the extra allowance.

The extra allowance will be the average monthly amount of approved months payable to the applicants in their I-WITS applications which were most recently submitted in the applicable period and eventually approved.

Click here for details.

The Transport Department today said that public transport operators will resume and strengthen services to meet the travelling needs of candidates sitting for the Hong Kong Diploma of Secondary Education Examination (DSE), which will start on April 24.

At the department's request, KMB, Citybus, New World First Bus and New Lantao Bus will resume bus routes serving school areas that were previously suspended, and will strengthen the services as appropriate to meet passenger demand.

For the Mass Transit Railway, except for the Airport Express and Disneyland Resort Line, heavy rail services will be gradually enhanced, starting from 6.15am to 6.30am during the exam period.

Light Rail and MTR bus services serving school areas will also be strengthened.

The department has reminded green minibus operators to closely monitor the transport demand and strengthen services as appropriate throughout the exam period.

Its Emergency Transport Co-ordination Centre will closely monitor the traffic situation and co-ordinate with major public transport operators to adjust frequency flexibly and strengthen services when necessary.

The department appealed to all DSE candidates to familiarise themselves with public transport routes to be taken to examination centres in advance and allow sufficient travelling time.

The Minimum Wage Commission will submit to the Chief Executive in Council its recommendation report on the statutory minimum wage rate by the end of October at the latest.

In accordance with the Minimum Wage Ordinance, the Chief Executive has required the commission to submit its recommendation report on or before October 31.

Pursuant to the ordinance, the commission must maintain an appropriate balance between the objectives of forestalling excessively low wages and minimising the loss of low-paid jobs as well as the need to sustain the city's economic growth and competitiveness.

The commission is conducting a public consultation on the statutory minimum wage rate review.

Views can be sent by email before June 16.

Click here for the consultation details.

The Treasury has announced a new set of financial measures aimed at helping startups during the coronavirus pandemic, including a £250 Future Fund for startups with at least £250,000 in funding

The Government will launch the Subsidy Scheme for Beauty Parlours, Massage Establishments & Party Rooms under the second round of the Anti-epidemic Fund on May 11.

A sum of $1.1 billion has been earmarked for the scheme, which is expected to benefit 12,400 beauty parlours and massage establishments as well as 500 party rooms.

The subsidy is expected to be disbursed from late this month.

Under the scheme, each eligible beauty parlour or massage establishment will receive a one-off tiered subsidy of $30,000, $60,000 or $100,000, depending on its number of workers.

Each eligible party room will receive a one-off subsidy of $40,000.

Applications will only be accepted online. The application deadline is May 17.

The scheme also covers premises which are operated by social enterprises.

For premises with business registration, social enterprise operators should file their applications through the online application system.

Those without business registration should directly approach the Hong Kong Council of Social Service at 2864 2993 or by email to obtain its certification and submit their applications.

Call 1836 188 or send an email for enquiries.

The Centre for Health Protection announced that as of 4pm today, no new COVID-19 cases have been recorded, leaving the number of confirmed cases in Hong Kong at 1,040 so far.

The centre again urged members of the public to maintain an appropriate social distance with other people in their daily lives to minimise the risk of infection.

People should go out less and avoid social activities such as having meals out or other gatherings to minimise the risk of coronavirus clusters emerging in the community.

As the COVID-19 situation remains severe and the number of cases reported around the world continues to rise, people are strongly urged to avoid all non-essential travel outside Hong Kong as well as maintain strict personal and environmental hygiene at all times.

Additionally, the Hospital Authority reported that there are currently 142 patients under isolation and that 920 patients have been discharged upon recovery.

For information and health advice on COVID-19, visit the Government's dedicated webpage.

The Centre for Health Protection announced that as of 4pm today, no new COVID-19 cases have been recorded, leaving the number of confirmed cases in Hong Kong at 1,040 so far.

The centre again urged members of the public to maintain an appropriate social distance with other people to minimise the risk of infection.

People should go out less and avoid social activities such as having meals out or other gatherings to minimise the risk of coronavirus clusters emerging in the community.

As the COVID-19 situation remains severe and the number of cases reported around the world continues to rise, people are strongly urged to avoid all non-essential travel outside Hong Kong as well as maintain strict personal and environmental hygiene at all times.

Additionally, the Hospital Authority reported that there are currently 127 patients under isolation and that 932 patients have been discharged upon recovery.

For information and health advice on COVID-19, visit the Government's dedicated webpage.

The Centre for Health Protection today announced it is investigating four additional confirmed COVID-19 cases.

The newly reported cases involve four males aged between 11 and 47. All of them travelled during the incubation period.

Epidemiological investigations and relevant contact tracing on the confirmed cases are ongoing.

The centre again urged the public to maintain an appropriate social distance from other people as much as possible to minimise the risk of infection.

People should go out less and avoid social activities such as having meals out or other gatherings to minimise the risk of outbreak clusters emerging in the community.

As the COVID-19 situation remains severe and the number of cases reported around the world continues to rise, people are strongly advised to avoid all non-essential travel outside Hong Kong as well as maintain strict personal and environmental hygiene at all times.

Additionally, the Hospital Authority reported that there are currently 120 patients under isolation and that 944 patients have been discharged upon recovery.

For information and health advice on COVID-19, visit the Government's dedicated webpage.

The Centre for Health Protection announced that as of 4pm today, no new COVID-19 cases have been recorded, leaving the number of confirmed cases in Hong Kong at 1,044 so far.

The centre again urged members of the public to maintain an appropriate social distance with other people to minimise the risk of infection.

It said people should go out less and avoid social activities such as having meals out or other gatherings to minimise the risk of coronavirus clusters emerging in the community.

As the COVID-19 situation remains severe and the number of cases reported around the world continues to rise, people are strongly urged to avoid all non-essential travel outside Hong Kong as well as maintain strict personal and environmental hygiene.

Additionally, the Hospital Authority reported that there are currently 109 patients under isolation and that 960 patients have been discharged upon recovery.

For information and health advice on COVID-19, visit the Government's dedicated webpage.

Secretary for Home Affairs Caspar Tsui visited the Physical Fitness Association of Hong Kong, China today to inspect its work in implementing the Fitness Centre Subsidy Scheme launched under the second phase of the Anti-epidemic Fund.

Mr Tsui said the scheme aims to provide a one-off subsidy of $100,000 to fitness centres to tide businesses over financial difficulties arising from anti-epidemic measures.

He thanked the association for handling the scheme’s applications.

Mr Tsui also expressed gratitude to the fitness industry for complying with the Government’s preventive measures, including suspension of business, in the fight against the virus.

Given the stabilising epidemic situation, the Government has conducted a health risk assessment and will allow premises, including fitness centres, to resume operations, Mr Tsui said, adding that he hopes the fitness industry will soon regain vitality.

The Home Affairs Bureau commissioned the association to assist in implementing the scheme, which opened for applications on May 4.

As of May 7, the association received 397 applications, of which more than half of them have been initially found to be eligible, involving subsidies of about $20 million.

The application period for the scheme will end on June 3.

Call 2302 9089 or send an email for enquiries.

More than 8,200 applications for the Anti-epidemic Support Scheme for Property Management Sector (ASPM) have been received, with over 3,850 approved, the Government announced today.

The approved applications involve subsidies of more than $140 million and will benefit around 22,000 building blocks and about 35,750 frontline property management workers.

Launched under the Anti-epidemic Fund, the ASPM provides subsidies to owners' organisations or property management companies of eligible buildings to provide hardship allowance to frontline property management workers.

It also provides the Anti-epidemic Cleansing Subsidy to owners' organisations or property management companies.

The scheme’s first phase covers private residential and composite buildings, while its second phase covers industrial and commercial buildings.

The ASPM is still open for applications and continues to disburse subsidies.

Contact the Property Management Services Authority at 3696 1156 or 3696 1166, or visit its website for details.

The Centre for Health Protection announced that as of 4pm today, no new COVID-19 cases have been recorded, leaving the number of confirmed cases in Hong Kong at 1,044 so far.

The centre again urged the public to maintain an appropriate social distance with other people to minimise the risk of infection.

It said people should go out less and avoid social activities such as having meals out or other gatherings to minimise the risk of coronavirus clusters emerging in the community.

As the COVID-19 situation remains severe and the number of cases reported around the world continues to rise, people are strongly urged to avoid all non-essential travel outside Hong Kong as well as maintain strict personal and environmental hygiene.

Additionally, the Hospital Authority reported that there are currently 90 patients under isolation and that 967 patients have been discharged upon recovery.

For information and health advice on COVID-19, visit the Government's dedicated webpage.

IntroductionThe nucleolus is the central organelle within eukaryotic cells whose primary function is to generate ribosomes, the major protein producing machines within all cells. New roles for the nucleolus are continuously emerging as we explore its molecular intricacies. Despite the central and fundamental role of the nucleolus in cell biology, there has previously been no single official meeting that enables the gathering of scientists whose research converges on the nucleolus. As a result, the community of researchers who study this organelle risks fragmentation across disciplines. The Emerging Roles for the Nucleolus Symposium, which has now taken place twice on a biennial basis, first in 2017 (1) and again in 2019, therefore, represents the first of its kind. The overarching goals of this symposium are (a) to convene researchers who study the nucleolus across model systems (yeast, nematodes, fruit flies, mouse, human cell lines) and biological perspectives (structural, biophysical, molecular, cellular, pathophysiology), (b) to share and disseminate the latest research breakthroughs in nucleolar biology, (c) to promote interaction, engagement, and collaboration centered on the nucleolus across disciplines, and (d) to provide trainees and early career investigators with an organelle-specific scientific community of support.The second Emerging Roles for the Nucleolus meeting was sponsored by the American Society for Biochemistry and Molecular Biology and was held at the Stowers Institute for Medical Research in Kansas City, MO, from October 24 to October 27, 2019. It was organized by Jennifer Gerton (Stowers Institute), Francesca Duncan (Northwestern University Feinberg School of Medicine), and Craig Pikaard...

We've all been saying it: These are unprecedented times. The impacts of the COVID-19 pandemic are incredibly wide-ranging and affect all facets of life. One that is hitting the scientific community very hard is the cancellation of meetings, large and small. While we are well-versed in connecting with colleagues and collaborators across a variety of online platforms, these do not replace the immensely gratifying aspects of attending meetings in person: the pleasure of catching up with old friends and making new ones, the insights gained from having real-time conversations with others working on the same topic but with different expertise and perspectives, and the stimulating new scientific ideas we carry home. We have all been feeling the disappointment as we learn that one meeting after another is forced to cancel, from the vibrant ASBMB annual meeting to summer conferences of all types.Another loss from the appropriate but painful decision to cancel the ASBMB annual meeting was the chance to hear from our Herbert Tabor Early Career Investigator Awardees, who represent the best science published in JBC in the preceding year. This year, the competition was particularly fierce. We hope and anticipate that we will be able to hear from the winners at next year's ASBMB annual meeting. But in the meantime, we want to raise a toast to Wenchao Zhao, Yue Yang, Manisha Dagar, Febin Varghese, and Ayumi Nagashima-Kasahara as our 2020 winners. We've captured their award-winning 2019 papers (1–5) on the JBC website (6), and extended profiles of the...

Sulfur is essential for biological processes such as amino acid biogenesis, iron–sulfur cluster formation, and redox homeostasis. To acquire sulfur-containing compounds from the environment, bacteria have evolved high-affinity uptake systems, predominant among which is the ABC transporter family. Theses membrane-embedded enzymes use the energy of ATP hydrolysis for transmembrane transport of a wide range of biomolecules against concentration gradients. Three distinct bacterial ABC import systems of sulfur-containing compounds have been identified, but the molecular details of their transport mechanism remain poorly characterized. Here we provide results from a biochemical analysis of the purified Escherichia coli YecSC-FliY cysteine/cystine import system. We found that the substrate-binding protein FliY binds l-cystine, l-cysteine, and d-cysteine with micromolar affinities. However, binding of the l- and d-enantiomers induced different conformational changes of FliY, where the l- enantiomer–substrate-binding protein complex interacted more efficiently with the YecSC transporter. YecSC had low basal ATPase activity that was moderately stimulated by apo FliY, more strongly by d-cysteine–bound FliY, and maximally by l-cysteine– or l-cystine–bound FliY. However, at high FliY concentrations, YecSC reached maximal ATPase rates independent of the presence or nature of the substrate. These results suggest that FliY exists in a conformational equilibrium between an open, unliganded form that does not bind to the YecSC transporter and closed, unliganded and closed, liganded forms that bind this transporter with variable affinities but equally stimulate its ATPase activity. These findings differ from previous observations for similar ABC transporters, highlighting the extent of mechanistic diversity in this large protein family.

Following its evoked release, dopamine (DA) signaling is rapidly terminated by presynaptic reuptake, mediated by the cocaine-sensitive DA transporter (DAT). DAT surface availability is dynamically regulated by endocytic trafficking, and direct protein kinase C (PKC) activation acutely diminishes DAT surface expression by accelerating DAT internalization. Previous cell line studies demonstrated that PKC-stimulated DAT endocytosis requires both Ack1 inactivation, which releases a DAT-specific endocytic brake, and the neuronal GTPase, Rit2, which binds DAT. However, it is unknown whether Rit2 is required for PKC-stimulated DAT endocytosis in DAergic terminals or whether there are region- and/or sex-dependent differences in PKC-stimulated DAT trafficking. Moreover, the mechanisms by which Rit2 controls PKC-stimulated DAT endocytosis are unknown. Here, we directly examined these important questions. Ex vivo studies revealed that PKC activation acutely decreased DAT surface expression selectively in ventral, but not dorsal, striatum. AAV-mediated, conditional Rit2 knockdown in DAergic neurons impacted baseline DAT surface:intracellular distribution in DAergic terminals from female ventral, but not dorsal, striatum. Further, Rit2 was required for PKC-stimulated DAT internalization in both male and female ventral striatum. FRET and surface pulldown studies in cell lines revealed that PKC activation drives DAT-Rit2 surface dissociation and that the DAT N terminus is required for both PKC-mediated DAT-Rit2 dissociation and DAT internalization. Finally, we found that Rit2 and Ack1 independently converge on DAT to facilitate PKC-stimulated DAT endocytosis. Together, our data provide greater insight into mechanisms that mediate PKC-regulated DAT internalization and reveal unexpected region-specific differences in PKC-stimulated DAT trafficking in bona fide DAergic terminals.

Purinergic signaling by extracellular ATP regulates a variety of cellular events and is implicated in both normal physiology and pathophysiology. Several molecules have been associated with the release of ATP and other small molecules, but their precise contributions have been difficult to assess because of their complexity and heterogeneity. Here, we report on the results of a gain-of-function screen for modulators of hypotonicity-induced ATP release using HEK-293 cells and murine cerebellar granule neurons, along with bioluminescence, calcium FLIPR, and short hairpin RNA–based gene-silencing assays. This screen utilized the most extensive genome-wide ORF collection to date, covering 90% of human, nonredundant, protein-encoding genes. We identified two ABCG1 (ABC subfamily G member 1) variants, which regulate cellular cholesterol, as modulators of hypotonicity-induced ATP release. We found that cholesterol levels control volume-regulated anion channel–dependent ATP release. These findings reveal novel mechanisms for the regulation of ATP release and volume-regulated anion channel activity and provide critical links among cellular status, cholesterol, and purinergic signaling.

Fatty acid transport protein 2 (FATP2) is highly expressed in the liver, small intestine, and kidney, where it functions in both the transport of exogenous long-chain fatty acids and the activation of very-long-chain fatty acids. Here, using a murine model, we investigated the phenotypic impacts of deleting FATP2, followed by a transcriptomic analysis using unbiased RNA-Seq to identify concomitant changes in the liver transcriptome. WT and FATP2-null (Fatp2−/−) mice (5 weeks) were maintained on a standard chow diet for 6 weeks. The Fatp2−/− mice had reduced weight gain, lowered serum triglyceride, and increased serum cholesterol levels and attenuated dietary fatty acid absorption. Transcriptomic analysis of the liver revealed 258 differentially expressed genes in male Fatp2−/− mice and a total of 91 in female Fatp2−/− mice. These genes mapped to the following gene ontology categories: fatty acid degradation, peroxisome biogenesis, fatty acid synthesis, and retinol and arachidonic acid metabolism. Targeted RT-quantitative PCR verified the altered expression of selected genes. Of note, most of the genes with increased expression were known to be regulated by peroxisome proliferator–activated receptor α (PPARα), suggesting that FATP2 activity is linked to a PPARα-specific proximal ligand. Targeted metabolomic experiments in the Fatp2−/− liver revealed increases of total C16:0, C16:1, and C18:1 fatty acids; increases in lipoxin A4 and prostaglandin J2; and a decrease in 20-hydroxyeicosatetraenoic acid. We conclude that the expression of FATP2 in the liver broadly affects the metabolic landscape through PPARα, indicating that FATP2 provides an important role in liver lipid metabolism through its transport or activation activities.

Numerous zinc ectoenzymes are metalated by zinc and activated in the compartments of the early secretory pathway before reaching their destination. Zn transporter (ZNT) proteins located in these compartments are essential for ectoenzyme activation. We have previously reported that ZNT proteins, specifically ZNT5–ZNT6 heterodimers and ZNT7 homodimers, play critical roles in the activation of zinc ectoenzymes, such as alkaline phosphatases (ALPs), by mobilizing cytosolic zinc into these compartments. However, this process remains incompletely understood. Here, using genetically-engineered chicken DT40 cells, we first determined that Zrt/Irt-like protein (ZIP) transporters that are localized to the compartments of the early secretory pathway play only a minor role in the ALP activation process. These transporters included ZIP7, ZIP9, and ZIP13, performing pivotal functions in maintaining cellular homeostasis by effluxing zinc out of the compartments. Next, using purified ALP proteins, we showed that zinc metalation on ALP produced in DT40 cells lacking ZNT5–ZNT6 heterodimers and ZNT7 homodimers is impaired. Finally, by genetically disrupting both ZNT5 and ZNT7 in human HAP1 cells, we directly demonstrated that the tissue-nonspecific ALP-activating functions of both ZNT complexes are conserved in human cells. Furthermore, using mutant HAP1 cells, we uncovered a previously-unrecognized and unique spatial regulation of ZNT5–ZNT6 heterodimer formation, wherein ZNT5 recruits ZNT6 to the Golgi apparatus to form the heterodimeric complex. These findings fill in major gaps in our understanding of the molecular mechanisms underlying zinc ectoenzyme activation in the compartments of the early secretory pathway.

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.