SRC-dependent signalling regulates actin ruffle formation induced by glycerophosphoinositol 4-phosphate

• Published in: Biochimica et biophysica acta 2008-12, Vol.1783 (12), p.2311-2322
• Main Authors: Filippi, Beatrice Maria, Mariggiò, Stefania, Pulvirenti, Teodoro, Corda, Daniela
• Format: Article
• Language: English
• Subjects: Actin cytoskeleton; Actins - metabolism; Animals; Calcium - metabolism; Calcium-Calmodulin-Dependent Protein Kinase Type 2 - antagonists & inhibitors; Calcium-Calmodulin-Dependent Protein Kinase Type 2 - metabolism; Cell Membrane - metabolism; Cells, Cultured; Enzyme Activation - drug effects; Fluorescent Antibody Technique; Glycerophosphoinositol; Guanine Nucleotide Exchange Factors - metabolism; Humans; Inositol 1,4,5-Trisphosphate - metabolism; Inositol Phosphates - pharmacology; Mice; NIH 3T3 Cells; Phosphoinositide; Phospholipase C gamma - antagonists & inhibitors; Phospholipase C gamma - metabolism; Phosphorylation; Protein Transport; Proto-Oncogene Proteins c-vav - metabolism; rac1 GTP-Binding Protein - metabolism; Signal Transduction; Signalling; src-Family Kinases - metabolism; T-Lymphoma Invasion and Metastasis-inducing Protein 1; Tyrosine kinase
• ISSN: 0167-4889; 0006-3002; 1879-2596
• DOI: 10.1016/j.bbamcr.2008.07.021

The glycerophosphoinositols are diffusible phosphoinositide metabolites reported to modulate actin dynamics and tumour cell spreading. In particular, the membrane permeant glycerophosphoinositol 4-phosphate (GroPIns4 P) 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 GroPIns4 P induces activation and translocation of Rac1 and its exchange factor TIAM1 to the plasma membrane; in addition, in in-vitro assays, GroPIns4 P favours the formation of a protein complex that includes Rac1 and TIAM1. Neither of these processes involves direct actions of GroPIns4 P 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 GroPIns4 P activates Src, and as a consequence, phospholipase Cγ and Ca 2+/calmodulin kinase II, the last of which directly phosphorylates TIAM1 and leads to TIAM1/Rac1-dependent ruffle formation.