Reorganization of actin cytoskeleton by the phosphoinositide metabolite glycerophosphoinositol 4-phosphate.
Glycerophosphoinositol 4-phosphate (GroPIns-4P) is a biologically active, water-soluble phospholipase A metabolite derived from phosphatidylinositol 4-phosphate, whose cellular concentrations have been reported to increase in Ras-transformed cells. It is therefore important to understand its biological activities. Herein, we have examined whether GroPIns-4P can regulate the organization of the actin cytoskeleton, because this could be a Ras-related function involved in cell motility and metastatic invasion. We find that in serum-starved Swiss 3T3 cells, exogenously added GroPIns-4P rapidly and potently induces the formation of membrane ruffles, and, later, the formation of stress fibers. These actin structures can be regulated by the small GTPases Cdc42, Rac, and Rho. To analyze the mechanism of action of GroPIns-4P, we selectively inactivated each of these GTPases. GroPIns-4P requires active Rac and Rho, but not Cdc42, for ruffle and stress fiber formation, respectively. Moreover, GroPIns-4P induces a rapid translocation of the green fluorescent protein-tagged Rac into ruffles, and increases the fraction of GTP-bound Rac, in intact cells. The activation of Rac by GroPIns-4P was near maximal and long-lasting. Interestingly, this feature seems to be critical in the induction of actin ruffles by GroPIns-4P.
Mancini
Raffaella
R
Department of Cell Biology and Oncology, Istituto di Ricerche Farmacologiche Mario Negri, Consorzio Mario Negri Sud, 66030 Santa Maria Imbaro, Chieti, Italy.
Piccolo
Enza
E
Mariggio'
Stefania
S
Filippi
Beatrice Maria
BM
Iurisci
Cristiano
C
Pertile
Paolo
P
Berrie
Christopher P
CP
Corda
Daniela
D
D016475:3T3 Cells; D000199:Actins / Q000378:metabolism*; D000818:Animals; D002461:Cell Line, Transformed; D002465:Cell Movement; D003599:Cytoskeleton / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D020558:GTP Phosphohydrolases / Q000737:chemistry; D049452:Green Fluorescent Proteins; D006133:Growth Substances / Q000378:metabolism; D007295:Inositol Phosphates / Q000378:metabolism*; D008164:Luminescent Proteins / Q000378:metabolism; D051379:Mice; D008856:Microscopy, Fluorescence; D009361:Neoplasm Invasiveness; D009362:Neoplasm Metastasis; D010716:Phosphatidylinositols / Q000737:chemistry*; D011994:Recombinant Proteins / Q000378:metabolism; D013997:Time Factors; D014162:Transfection; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism
D000199:Actins; D006133:Growth Substances; D007295:Inositol Phosphates; D008164:Luminescent Proteins; D010716:Phosphatidylinositols; D011994:Recombinant Proteins; C062528:glycero-3-phosphoinositol 4-phosphate; D049452:Green Fluorescent Proteins; D020558:GTP Phosphohydrolases; D020764:cdc42 GTP-Binding Protein