Abstract
Purpose :
To understand the cytosolic and nuclear role(s) of actin cytoskeletal and cell adhesive proteins in trabecular meshwork (TM) cells in the context of aqueous humor outflow
Methods :
Nuclear and cytosolic fractions isolated from primary cultures of human TM cells treated with dexamethasone for various lengths of time were subjected to quantitative proteomics analysis. The distribution and colocalization of AgrBP2 and its related c-Cbl associated protein (CAP/Ponsin) with actin cytoskeletal and focal adhesions proteins, and the dexamethasone-induced reorganization of these proteins in human TM cells were evaluated by immunofluorescence and immunoblotting analyses.
Results :
Dexamethasone treatment (0.5 µM for 5-7 days) led to a significant increase in the levels of ArgBP2 (SORBS2) and CAP (SORBS1), which are the sorbin and SH3-domain containing, and flotillin interacting adaptor proteins, in both, the nuclear and cytosolic fractions of human TM cells. The increase in ArgBP2 levels was consistent in more than ten biological replicates of TM cells analyzed. While CAP exhibited a focal adhesion-specific distribution profile, ArgBP2 was found to colocalize with actin stress fibers and ZO-1, and distribute to the focal adhesions, lamellipodia, and nucleus. Upregulation of ArgBP2 and CAP in dexamethasone treated TM cells was associated with increased levels of chromatin remodelers including BRG1, MAT1 and MECP2. The Abl and Arg kinase inhibitor, dasatinib, was found to suppress dexamethasone-induced association of ArgBP2 and CAP with focal adhesions. Interestingly, the chromosomal localization of ArgBP2 at 4q35.1 is a recognized locus for an autosomal dominant POAG.
Conclusions :
Taken together, ArgBP2 and its related cell adhesive proteins (CAP and Vinexin) appear to play a key role in dexamethasone-induced actin cytoskeletal crosslinking and cell adhesive interactions in TM cells, which are known to influence aqueous humor outflow and intraocular pressure.
This is a 2021 ARVO Annual Meeting abstract.