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The a subunit is the largest of 14 different subunits that make up the V-ATPase complex. In mammalian species this membrane protein has four paralogous isoforms, a1-a4. Clinically, a subunit isoforms are implicated in diverse diseases; however, little is known about their structure and function. The subunit has conserved, predicted N-glycosylation sites, and the a3 isoform has been directly shown to be N-glycosylated. Here we ask if human a4 (ATP6V0A4) is N-glycosylated at the predicted site, Asn489. We transfected HEK 293 cells, using the pCDNA3.1 expression-vector system, to express cDNA constructs of epitope-tagged human a4 subunit, with or without mutations to eliminate the putative glycosylation site. Glycosylation was characterized also by treatment with endoglycosidases; expression and localization were assessed by immunoblotting and immunofluorescence. Endoglycosidase-treated wild type (WT) a4 showed increased relative mobility on immunoblots, compared with untreated WT a4. This relative mobility was identical to that of unglycosylated mutant a4 , demonstrating that the a4 subunit is glycosylated. Cycloheximide pulse-chase experiments showed that the unglycosylated subunit degraded at a higher rate than the N-glycosylated form. Unglycosylated a4 was degraded mostly in the proteasomal pathway, but also, in part, through the lysosomal pathway. Immunofluorescence colocalization data showed that unglycosylated a4 was mostly retained in the ER, and that plasma membrane trafficking was defective. Co-immunoprecipitation studies suggested that a4 does not assemble with the V-ATPase V domain. Taken together, these data show that N-glycosylation plays a crucial role in a4 stability, and in V-ATPase assembly and trafficking to the plasma membrane. J. Cell. Biochem. 117: 2757-2768, 2016. © 2016 Wiley Periodicals, Inc.

Infection with the SARS-CoV-2 virus has rapidly become a global pandemic for which we were not prepared. Several clinical trials using previously approved drugs and drug combinations are urgently underway to improve our current situation. Unfortunately, a vaccine option is optimistically at least a year away. It is imperative that for future viral pandemic preparedness, we have a rapid screening technology for drug discovery and repurposing. The primary purpose of this research project was to evaluate the DeepNEU stem-cell based platform by creating and validating computer simulations of artificial lung cells infected with SARS-CoV-2 to enable the rapid identification of antiviral therapeutic targets and drug repurposing. The data generated from this project indicate that (a) human alveolar type lung cells can be simulated by DeepNEU (v5.0), (b) these simulated cells can then be infected with simulated SARS-CoV-2 virus, (c) the unsupervised learning system performed well in all simulations based on available published wet lab data, and (d) the platform identified potentially effective anti-SARS-CoV2 combinations of known drugs for urgent clinical study. The data also suggest that DeepNEU can identify potential therapeutic targets for expedited vaccine development. We conclude that based on published data plus current DeepNEU results, continued development of the DeepNEU platform will improve our preparedness for and response to future viral outbreaks. This can be achieved through rapid identification of potential therapeutic options for clinical testing as soon as the viral genome has been confirmed.

BACKGROUND. The role of humoral immunity in the coronavirus disease 2019 (COVID-19) is not fully understood owing, in large part, to the complexity of antibodies produced in response to the SARS-CoV-2 infection. There is a pressing need for serology tests to assess patient-specific antibody response and predict clinical outcome. METHODS. Using SARS-CoV-2 proteome and peptide microarrays, we screened 146 COVID-19 patients plasma samples to identify antigens and epitopes. This enabled us to develop a master epitope array and an epitope-specific agglutination assay to gauge antibody responses systematically and with high resolution. RESULTS. We identified linear epitopes from the Spike (S) and Nucleocapsid (N) protein and showed that the epitopes enabled higher resolution antibody profiling than the S or N protein antigen. Specifically, we found that antibody responses to the S(811-825), S(881-895) and N(156-170) epitopes negatively or positively correlated with clinical severity or patient survival. Moreover, we found that the P681H and S235F mutations associated with the coronavirus variant of concern B.1.1.7 altered the specificity of the corresponding epitopes. CONCLUSIONS. Epitope-resolved antibody testing not only affords a high-resolution alternativeto conventional immunoassays to delineate the complex humoral immunity to SARS-CoV-2 and differentiate between neutralizing and non-neutralizing antibodies, it may potentially be used to predict clinical outcome. The epitope peptides can be readily modified to detect antibodies against variants of concern (VOC) in both the peptide array and latex agglutination formats.

The a subunit is the largest of 15 different subunits that make up the vacuolar H + -ATPase (V-ATPase) complex, where it functions in proton translocation. In mammals, this subunit has four paralogous isoforms, a1-a4, which may encode signals for targeting assembled VATPases to specific intracellular locations. Despite the functional importance of the a subunit, its structure remains controversial. By studying molecular mechanisms of human disease-causing missense mutations within a subunit isoforms, we may identify domains critical for V-ATPase targeting, activity and/or regulation.cDNA . Coimmunoprecipitation studies revealed an increase in association of a4 R449H with the V0 assembly factor VMA21, and a reduced association with the V1 sector subunit, ATP6V1B1 (B1). For a4 G820R , where stability, degradation and trafficking were relatively unaffected, 3D molecular modeling suggested that the mutation causes dRTA by blocking the proton pathway. This study provides critical information that may assist rational drug design to manage dRTA and cutis laxa. Vacuolar H+ -ATPases (V-ATPases) are conserved, multisubunit rotary proton pumps that play crucial roles in regulating the pH of cells and their intracellular compartments (1-5). They can be categorized as endomembrane or plasma membrane V-ATPases, based on their subcellular localization (6,7). Endomembrane V-ATPases are expressed in all eukaryotic cells in the membranes of acidic organelles like lysosomes, endosomes and the Golgi apparatus, where they translocate protons to acidify the luminal compartments of the organelles (8). Plasma membrane V-ATPases traffic to the surfaces of some specialized cells, such as osteoclasts, kidney intercalated cells and metastatic cancer cells, where they secrete protons into the extracellular fluid (6,9-11).The V-ATPase complex consists of 15 different subunits arranged into two major sectors, the http://www.jbc.org/cgi