Localization of phospholipase C‐γ1 signaling in caveolae: importance in EGF‐induced phosphoinositide hydrolysis but not in tyrosine phosphorylation

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Abstract
Upon epidermal growth factor treatment, phospholipase C‐γ1 (PLC‐γ1) translocates from cytosol to membrane where it is phosphorylated at tyrosine residues. Caveolae are small plasma membrane invaginations whose structural protein is caveolin. In this study, we show that the translocation of PLC‐γ1 and its tyrosine phosphorylation are localized in caveolae by caveolin‐enriched low‐density membrane (CM) preparation and immunostaining of cells. Pretreatment of cells with methyl‐β‐cyclodextrin (MβCD), a chemical disrupting caveolae structure, inhibits the translocation of PLC‐γ1 to CM as well as phosphatidylinositol (PtdIns) turnover. However, MβCD shows no effect on tyrosine phosphorylation level of PLC‐γ1. Our findings suggest that, for proper signaling, PLC‐γ1 phosphorylation has to occur at PtdInsP2‐enriched sites.