Plasma membrane-actin assemblies play an important role in several cell processes, as well as cell organization and integrity. Disruption of these protein associations may be the basis for several disease processes, particularly cell transformation. Only a limited number of functional membrane-actin cytoskeletal protein associations, such as integrin and dystrophin, have been defined and analyzed in vertebrate, nonerythroid cells. Through a combination of biochemical and immunological approaches along with protein microsequence analyses, we have discovered a novel actin and caveolin-associated integral plasma membrane glycoprotein, gp 105, which we also refer to as cavactilin. Gp 105 or cavactilin has an intriguing cell surface distribution in that it is concentrated in 20-30 m surface domains almost exclusively along the trailing end of motile chicken embryo fibroblasts (CHF). These are sites where the cell surface is underlain by actin microfilaments and where plasma membrane invaginations known as caveolae exist. Lateral surface patches of gp 105 in CHF can be correlated with a single microfilament bundle and also colocalized with p22 (caveolin), a marker for the plasma membrane caveolae [Rothberg et al. (1992) Cell 68: 673-682]. Gp 105 can also assume in vitro associations with caveolin since immunoaffinity chromatography eluates from MAb 12-11 (gp 105) and MAb Z034 (caveolin) column have significant levels of gp 105 and caveolin. Direct interaction of purified (caveolin-free), nondenatured forms of gp 105 with purified chicken gizzard actin has been shown in G and F-actin binding assays and F-actin sedimentation experiments. Our major hypothesis is that gp 105 (cavactilin) associations with actin, caveolin protein complexes and other actin-associated proteins play an important function in the contractility events of cells and in actin-related force coupling events which regulate or mediate cell signalling occuring at the plasma membrane caveolae sites, the "message centers of the cell" [Anderson. (1993) Proc. Natl. Acad. Sci. USA 90: 10909-10913]. Our research program involves a comprehensive biochemical, molecular (gene cloning) and immunological analyses of gp 105. Other studies include investigation of gp 105 interaction with actin and caveolin in normal and Rous sarcoma virus-transformed CHF and dynamic changes in gp 105 cell surface domain topology in living cells.
Publications:
1. Rogalski-Wilk, A.A., A. Skepner, G. Venugopal, and R. Donati . 1992. Studies on a novel integral membrane protein-cytoskeletal complex in chicken embryo fibroblasts. Mol. Biol. Cell.3: 268a.
2. Rogalski-Wilk, A.A., A. Skepner, R. Donati, and G. Venugopal. 1994. A population of highly purified gp 105 (cavactilin), a novel chick integral plasma membrane glycoprotein, directly binds actin. Mol. Biol. Cell. 5: 422a.
3. Rogalski-Wilk, A.A., R. Donati, A. Skepner, and G. Venugopal. 1994. Gp 105 (cavactilin), a novel chick integral plasma membrane glycoprotein, has associations with actin and p22 (caveolin) protein complexes and surface domains. J. Cell. Biol. (manuscript in revision).