Open AccessDorsal ruffles enhance activation of Akt by growth factors
Author(s) -
Sei Yoshida,
Regina Pacitto,
Catherine Sesi,
Leszek Kotula,
Joel A. Swanson
Publication year - 2018
Publication title -
journal of cell science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.384
H-Index - 278
eISSN - 1477-9137
pISSN - 0021-9533
DOI - 10.1242/jcs.220517
Subject(s) - nocodazole , protein kinase b , phosphorylation , pi3k/akt/mtor pathway , biology , epidermal growth factor , platelet derived growth factor receptor , microbiology and biotechnology , phosphatidylinositol , growth factor , signal transduction , biochemistry , receptor , cell , cytoskeleton
In fibroblasts, platelet-derived growth factor (PDGF) and epidermal growth factor (EGF) stimulate the formation of actin-rich, circular dorsal ruffles (CDR) and phosphatidylinositol 3-kinase (PI3K)-dependent phosphorylation of Akt. To test the hypothesis that CDR increase synthesis of phospho-Akt (pAkt), we analyzed the contributions of CDR to Akt phosphorylation in response to PDGF and EGF. CDR appeared within several minutes of growth factor addition, coincident with a peak of pAkt. Microtubule depolymerization with nocodazole blocked CDR formation and inhibited phosphorylation of Akt in response to EGF but not PDGF. Quantitative immunofluorescence showed increased concentrations of Akt, pAkt and PIP3, the phosphoinositide product of PI3K that activates Akt, concentrated in CDR and ruffles. EGF stimulated lower maximal levels of pAkt than did PDGF, which suggested that Akt phosphorylation requires amplification in CDR only when PI3K activities are low. Accordingly, stimulation with low concentrations of PDGF elicited lower levels of Akt phosphorylation, which, like responses to EGF, were inhibited by nocodazole. These results indicate that when receptor signaling generates low levels of PI3K activity, CDR facilitate local amplification of PI3K and phosphorylation of Akt.