Interaction of shrimp ras protein with mammalian caveolin-1

BALB/3T3 cells were transformed by transfection with DNA encoding the mutated ras(Q61K) from shrimp Penaeus japonicus (Huang and Chuang. 1999. J Exp Zool 283:510–521). The caveolin‐1 in the membrane fraction extractable with 2% octyl glucoside was significant reduced, compared to untransformed cells. To understand this in more detail, the interaction of S‐Ras with caveolin was investigated using caveolin‐1 purified from rat lungs. The purified caveolin‐1 binds c‐Src, suppressing its autophosphorylation. It also binds to phosphatidylserine‐cholesterol liposomes. These reconstituted caveolin‐phosphatidylserine‐cholesterol vesicles, which act as a model of caveolae, recruit both bacterially expressed S‐Ras and rat KB‐Ras proteins, as demonstrated on western blots with antibodies against caveolin‐1 and Ras. Caveolin‐1 suppressed the intrinsic GTPase activity of S‐Ras, sustaining it in the active GTP bound form. By contrast, caveolin‐1 enhanced the intrinsic GTPase activity of KB‐Ras, to convert it into the inactive GDP‐bound form. These events suggest that caveolin may act as a docking site for Ras proteins and may be able to either maintain or alter their activity state. These events may be associated with the ability of S‐ras(Q61K) to successfully transform cells. J. Exp. Zool. 287:432–439, 2000. © 2000 Wiley‐Liss, Inc.