Identification of a novel Rac1-interacting protein involved in membrane ruffling.
The Rac GTP binding proteins are implicated in actin cytoskeleton-membrane interaction in mammalian cells. In fibroblast cells, Rac has been shown to mediate growth factor-induced polymerization of actin to form membrane ruffles and lamellipodia. We report here the isolation of a noval Rac1-interacting protein, POR1. POR1 binds directly to Rac1, and the interaction of POR1 with Rac1 is GTP dependent. A mutation in the Rac1 effector binding loop shown to abolish membrane ruffling also abolishes interaction with POR1. Truncated versions of POR1 inhibit the induction of membrane ruffling by an activated mutant of Rac1, V12Rac1, in quiescent rat embryonic fibroblast REF52 cells. Furthermore, POR1 synergizes with an activated mutant of Ras, V12Ras, in the induction of membrane ruffling. These results suggest a potential role for POR1 in Rac1-mediated signaling pathways.
Van Aelst
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Cold Spring Harbor Laboratory, PO Box 100, Cold Spring Harbor, NY 11724, USA.
Joneson
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Bar-Sagi
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D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D002352:Carrier Proteins / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D019143:Evolution, Molecular; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D017354:Point Mutation; D051381:Rats; D015398:Signal Transduction; D020744:rac GTP-Binding Proteins
C101158:ARFIP2 protein, human; D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D006160:Guanosine Triphosphate; D019204:GTP-Binding Proteins; D020744:rac GTP-Binding Proteins