Recent investigations have focused on characterizing the molecular components of the podocyte intercellular junction, because several of these components, including Nephrin, are functionally necessary for development of normal podocyte structure and filter integrity. Accumulating evidence suggests that the Nephrin-associated protein complex is a signaling nexus.

As a putative cell adhesion molecule of the immunoglobulin superfamily, nephrin likely participates in cell-cell interactions between podocyte foot processes and may represent a component of the slit diaphragm.

Glomerular visceral epithelial cells (podocytes) appear to play a central role in maintaining the selective filtration barrier of the renal glomerulus. While the immunoglobulin superfamily member Nephrin was proposed to act as a cell adhesion molecule at the podocyte intercellular junction necessary for maintaining glomerular perm selectivity, the Nephrin ligand has not been identified. The existence of a new subfamily of Nephrin-like molecules including Neph1 was recently described. Genetic deletion of Nephrin or Neph1 resulted in similar phenotypes of podocyte foot process effacement and proteinuria. The subcellular localization of Neph1 and the possibility that Nephrin and Neph1 interact was investigated. Polyclonal antiserum for Neph1 was raised and characterized. Neph1 migrated as a 90-kDa protein on SDS-PAGE under reducing conditions. Neph1 was identified in a glomerular and podocyte-specific distribution in adult rat kidney. Like Nephrin and Podocin, Neph1 was enriched in Triton X-100 detergent-resistant membrane fractions. Consistent with this observation, immunogold electron microscopy demonstrated that Neph1 localized exclusively to lateral margins of podocyte foot processes at the insertion of the slit diaphragm. Neph1 and Nephrin participate in a direct cis-interaction involving their cytoplasmic domains. In addition, interactions between the extracellular domain of Nephrin and itself and between the extracellular domain of Nephrin and that of Neph1 were detected. Neph1 did not interact via a homophilic interaction. These observations suggest that Nephrin and Neph1 form a hetero-oligomeric receptor complex in the plane of the membrane that might interact across the foot process intercellular junction through interactions between Nephrin with itself and Neph1.

Expression of the arginase (CAR1) gene in Saccharomyces cerevisiae is induced by arginine or its analog homoarginine. Induction has been previously shown to require a negatively acting upstream repression sequence, which maintains expression of the gene at a low level in the absence of inducer. The objective of this work was to identify the cis-acting elements responsible for CAR1 transcriptional activation and response to inducer. We identified three upstream activation sequences (UASs) that support transcriptional activation in a heterologous expression vector. Two of these UAS elements function in the absence of inducer, whereas the third functions only when inducer is present. One of the inducer-independent UAS elements exhibits significant homology to the Sp1 factor-binding sites identified in simian virus 40 and various mammalian genes.

Darunavir and tipranavir are two inhibitors that are active against multi-drug resistant (MDR) HIV-1 protease variants. In this study, the in vitro inhibitory efficacy was tested against a MDR HIV-1 protease variant, MDR 769 82T, containing the drug resistance mutations of 46L/54V/82T/84V/90M. Crystallographic and enzymatic studies were performed to examine the mechanism of resistance and the relative maintenance of potency. The key findings are as follows: (i) The MDR protease exhibits decreased susceptibility to all nine HIV-1 protease inhibitors approved by the U.S. Food and Drug Administration (FDA), among which darunavir and tipranavir are the most potent; (ii) the threonine 82 mutation on the protease greatly enhances drug resistance by altering the hydrophobicity of the binding pocket; (iii) darunavir or tipranavir binding facilitates closure of the wide-open flaps of the MDR protease; and (iv) the remaining potency of tipranavir may be preserved by stabilizing the flaps in the inhibitor-protease complex while darunavir maintains its potency by preserving protein main chain hydrogen bonds with the flexible P2 group. These results could provide new insights into drug design strategies to overcome multi-drug resistance of HIV-1 protease variants.

Zika virus (ZIKV) is a flavivirus spread by daytime-active Aedes spp. mosquitoes such as A. aegypti and A. albopictus. Previously thought to be a mild infection, the latest ZIKV outbreak in the Americas is causally associated with more severe symptoms as well as severe birth defects, such as microcephaly. Currently no vaccine or antiviral exists. However, recent progress has demonstrated the viral NS2B/NS3 protease may be a suitable target for the development of small-molecule antiviral agents. To better understand the ZIKV protease, we expressed, purified, and characterized unlinked and linked NS2B/NS3 protease corresponding to an isolate from the recent outbreak in Puerto Rico. Unlinked ZIKV protease is more active and binds substrate with greater affinity than linked ZIKV protease. Therefore, we propose that unlinked ZIKV protease be used when evaluating or designing ZIKV protease inhibitors. Additionally, potent inhibitors of related viral proteases, like West Nile Virus and Dengue virus, may serve as advanced starting points to identify and develop ZIKV protease inhibitors.

No abstract

From a collection of monoclonal antibodies (MAbs) that recognize the native structure of the toxincoregulated pilus of Vibrio cholerae, two protective MAbs (16.1 and 169.1) were used to localize the corresponding epitopes on the pilus. These MAbs were shown to specifically recognize the carboxyl half of the TcpA pilin subunit, as determined by their recognition of proteolytic fragments and hybrid pilin proteins. The positions of the epitopes were precisely determined through the use of overlapping synthetic peptides corresponding to this region of the pilin. The MAbs were found to recognize adjacent peptides, delineating a region between residues 157 and 199. Since the protective nature is specific for these two antibodies, the findings suggest that this region defines a domain that participates in toxin-coregulated pilus-mediated colonization and therefore represents a target for studies of its potential as an immunogen for incorporation into a component cholera vaccine.