SRC-dependent signalling regulates actin ruffle formation induced by glycerophosphoinositol 4-phosphate.
The glycerophosphoinositols are diffusible phosphoinositide metabolites reported to modulate actin dynamics and tumour cell spreading. In particular, the membrane permeant glycerophosphoinositol 4-phosphate (GroPIns4P) has been shown to act at the level of the small GTPase Rac1, to induce the rapid formation of membrane ruffles. Here, we have investigated the signalling cascade involved in this process, and show that it is initiated by the activation of Src kinase. In NIH3T3 cells, exogenous addition of GroPIns4P induces activation and translocation of Rac1 and its exchange factor TIAM1 to the plasma membrane; in addition, in in-vitro assays, GroPIns4P favours the formation of a protein complex that includes Rac1 and TIAM1. Neither of these processes involves direct actions of GroPIns4P on these proteins. Thus, through the use of specific inhibitors of tyrosine kinases and phospholipase C (and by direct evaluation of kinase activities and inositol 1,4,5-trisphosphate production), we show that GroPIns4P activates Src, and as a consequence, phospholipase Cgamma and Ca(2+)/calmodulin kinase II, the last of which directly phosphorylates TIAM1 and leads to TIAM1/Rac1-dependent ruffle formation.
Filippi
Beatrice Maria
BM
Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Via Nazionale 8/A, 66030 Santa Maria Imbaro, Chieti, Italy.
Mariggiò
Stefania
S
Pulvirenti
Teodoro
T
Corda
Daniela
D
D000199:Actins / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000037:antagonists & inhibitors / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D004789:Enzyme Activation / Q000187:drug effects; D005455:Fluorescent Antibody Technique; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D007295:Inositol Phosphates / Q000494:pharmacology*; D051379:Mice; D041681:NIH 3T3 Cells; D051966:Phospholipase C gamma / Q000037:antagonists & inhibitors / Q000378:metabolism; D010766:Phosphorylation; D021381:Protein Transport; D051567:Proto-Oncogene Proteins c-vav / Q000378:metabolism; D015398:Signal Transduction; D000075684:T-Lymphoma Invasion and Metastasis-inducing Protein 1; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*; D019061:src-Family Kinases / Q000378:metabolism*
D000199:Actins; D020662:Guanine Nucleotide Exchange Factors; D007295:Inositol Phosphates; D051567:Proto-Oncogene Proteins c-vav; D000075684:T-Lymphoma Invasion and Metastasis-inducing Protein 1; C513260:Tiam1 protein, mouse; C062528:glycero-3-phosphoinositol 4-phosphate; D015544:Inositol 1,4,5-Trisphosphate; D019061:src-Family Kinases; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D051966:Phospholipase C gamma; D020830:rac1 GTP-Binding Protein; D002118:Calcium