Biology subjects

Regmi, S. C.

Publications and source records attributed to Regmi, S. C..

3 recordsLinked to original sources

bioRxiv2019

Core-2 O-glycans are required for Galectin-3 interaction with the osteoarthritis related protein lubricin

Synovial fluid lubricin (proteoglycan 4) is a mucin-type O-linked glycosylated (60% of the mass) biological lubricant involved in osteoarthritis (OA) development. Lubricin has been reported to be cross-linked by synovial galectin-3 on the lubricating articular surface. Here, we confirm that binding to galectin-3 depended on core-2 O-linked glycans, where surface plasmon resonance of a recombinant lubricin (rhPRG4) devoid of core-2 structures lacked binding capacity to recombinant galectin-3. Both galectin-3 levels and interactions with synovial lubricin were found to be decreased in late-stage OA patients coinciding with an increase of truncated and less sialylated core 1 O-glycans. These data suggest a defect cross-linking of surface active molecules in OA and provides novel insights into OA molecular pathology.

biochemistry↗

bioRxiv2019

TAK1 Regulates Endothelial Integrity Through Stabilization of Junctions via GSK3β and FoxO1

TLR4 signaling in endothelial cells (ECs) induces vascular injury by disrupting the endothelial junctional barrier. However, it is not known whether TLR4 signaling can also promote endothelial barrier repair after vascular injury. Here we addressed the role of TAK1 activation downstream of TLR4 in the mechanism of vascular integrity. In inducible EC-restricted TAK1 knockout (TAK1i{Delta}EC) mice, the endothelial barrier was compromised. Blocking TAK1 activity caused spontaneous loss of the endothelial barrier. Importantly, TAK1 inactivated GSK3{beta} via AKT to prevent {beta}-catenin downregulation. We observed in ECs of GSK3{beta}i{Delta}EC mice an increase in {beta}-catenin transfer to the nucleus to form a complex with transcription factor FoxO1, thus repressing the expression of the tight junction protein claudin-5 and causing vascular leak. Strikingly, in TAK1i{Delta}EC mice, FoxO1 expression was dramatically increased while expression of AKT was suppressed, and in vivo inhibition of FoxO1 prevented sepsis-induced lung vascular leak in GSK3{beta}i{Delta}EC and TAK1i{Delta}EC mice. Further, EC-restricted deletion of FoxO1 in mice suppressed sepsis-induced lung vascular leak and mortality. Our findings point to the potential of targeting the TAK1-AKT-GSK3{beta}-FoxO1 axis as a therapeutic approach to treat uncontrolled lung vascular leak in sepsis.

cell biology↗

bioRxiv2019

EphB1 in Endothelial Cells Regulates Caveolae Formation and Endocytosis

Caveolae, the cave-like structures abundant in endothelial cells (ECs), are important in regulating key functions such as caveolae-mediated endocytosis and generation of nitric oxide. Here we show that deletion of the receptor tyrosine kinase EphB1 (EphB1-/-) in mice markedly reduced the caveolae number in ECs of heart and lung vessels and prevented caveolae-mediated endocytosis. EphB1 expressed in adult ECs was shown to bind the caveolin-1 (Cav-1) scaffold domain (CSD) via the CSD binding motif (CSDBM) on EphB1. We demonstrated that activation of EphB1 by the native ligand Ephrin B1 uncoupled EphB1 from Cav-1, and licensed Src-dependent Y-14 Cav-1 phosphorylation. Deletion of CSDBM on EphB1 prevented EphB1/Cav-1 interaction and the activation of Src and Src mediated Y-14 Cav-1 phosphorylation. These studies identify the central role of endothelium expressed EphB1 in regulating caveolae biogenesis and caveolae-mediated endocytosis.

cell biology↗