A PLCδ₁‐binding protein, p122/RhoGAP, is localized in caveolin‐enriched membrane domains and regulates caveolin internalization

Abstract

A GTPase activating protein (GAP), p122, has previously been cloned as a phospholipase C (PLC)δ δ δ δ 1 -interacting protein. p122 shows a specific GAP activity for Rho and enhances the enzyme activity of PLCδ δ δ δ 1 . In this study, we examined the localization and functions of p122/RhoGAP, using enhanced green fluorescent protein (EGFP)-tagged proteins. EGFP-p122 was observed as punctate structures at the plasma membrane of BHK (fibroblastic) cells and MDCK (epithelial) cells. This patchy distribution depended on membrane cholesterol levels and the C-terminal region of p122 containing the GAP domain was responsible for it. Sucrose density gradient centrifugation and immunostaining of caveolin-1 revealed that p122 was localized in caveolin-enriched membrane domains mainly via its GAP domain. We demonstrated that transient expression of EGFP-p122 caused internalization of caveolin-1. Moreover, when the EGFP-tagged GAP domain was introduced in another fibroblastic cell line, NRK cells, punctate fluorescent structures were co-localized with caveolin-1. In this case, caveolin-1-positive structures were found in patches of F-actin, unlike those of untransfected cells that formed linear arrays along with actin stress fibres. These results suggest that p122 is localized in caveolae and plays an important role in caveolin distribution through reorganization of the actin cytoskeleton.

Les protéines à domaine START, des trafiquants intracellulaires de lipides

“…En accord avec cette localisation, les cellules dépourvues de STARD12 ont des anomalies du cytosquelette et le domaine Rho-GAP intervient dans ce phénomène [24]. STARD12 est aussi localisée dans les cavéoles, des micro-domaines invaginés de la membrane plasmique riches en cholestérol et caractérisés par la présence de la protéine cavéoline [31]. Quelques protéines START sont cytosoliques, comme STARD2, STARD4, STARD5.…”

Oncogenic inhibition by a deleted in liver cancer gene requires cooperation between tensin binding and Rho-specific GTPase-activating protein activities

“…The RhoGAP activity appears to be required for these antioncogenic activities because RhoGAP-deficient mutants have reduced biological activity. The DLC1 protein is reported to have a peripheral cellular location, and the rat homolog has been localized to caveolae and focal adhesions (6,14,15).…”

Effects of Structure of Rho GTPase-activating Protein DLC-1 on Cell Morphology and Migration

“…Several reports suggest that DLC-1 is localized at focal adhesions (20 -22), whereas another study described localization to caveolae (23), and a third study found a diffuse distribution in the cytosol (7). The related DLC-2 and DLC-3 proteins have also been reported to localize to focal adhesions (10,24).…”