title: MARCKS regulates lamellipodia formation induced by IGF-I via association with PIP2 and beta-actin at membrane microdomains.
abstract: Myristoylated alanine-rich C kinase substrate (MARCKS) is considered to participate in formation of F-actin-based lamellipodia, which represents the first stage of neurite formation. However, the mechanism of how MARCKS is involved in lamellipodia formation is not precisely unknown. Using SH-SY5Y cells, we demonstrated here that MARCKS was translocated from cytosol to detergent-resistant membrane microdomains, known as lipid rafts, within 30 min after insulin-like growth factor-I (IGF-I) stimulation, which was accompanied by MARCKS dephosphorylation, beta-actin accumulation in lipid rafts, and lamellipodia formation. The protein kinase C inhibitor, Ro-31-8220, and Rho-kinase inhibitors, HA1077 and Y27632, themselves decreased basal phosphorylation levels of MARCKS and coincidently elicited translocation of MARCKS to lipid rafts. On the other hand, the phosphoinositide 3-kinase inhibitor, LY294002, abolished IGF-I-induced dephosphorylation, translocation of MARCKS to lipid rafts, and lamellipodia formation. Treatment of cells with neomycin, a PIP2-masking reagent, attenuated the translocation of MARCKS to lipid rafts and the lamellipodia formation induced by IGF-I, although dephosphorylation of MARCKS was not affected. Immunocytochemical and immunoprecipitation analysis indicated that IGF-I stimulation induced the translocation of MARCKS to lipid rafts in the edge of lamellipodia and formation of the complex with PIP2. Moreover, we demonstrated that knockdown of endogenous MARCKS resulted in significant attenuation of IGF-I-induced beta-actin accumulation in the lipid rafts and lamellipodia formation. These results suggest a novel role for MARCKS in lamellipodia formation induced by IGF-I via the translocation of MARCKS, association with PIP2, and accumulation of beta-actin in the membrane microdomains.
authors.affiliation: Laboratory of Pharmacology, School of Pharmaceutical Science, Kitasato University, Tokyo, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Yamaguchi
authors.forename: Mitsuya
authors.initials: M
authors.lastname: Shiraishi
authors.forename: Kiyoko
authors.initials: K
authors.lastname: Fukami
authors.forename: Atsuhiro
authors.initials: A
authors.lastname: Tanabe
authors.forename: Yuri
authors.initials: Y
authors.lastname: Ikeda-Matsuo
authors.forename: Yasuhito
authors.initials: Y
authors.lastname: Naito
authors.forename: Yasuharu
authors.initials: Y
authors.lastname: Sasaki
mesh_terms: D000199:Actins / Q000378:metabolism*; D001932:Brain Neoplasms; D045744:Cell Line, Tumor; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D021962:Membrane Microdomains / Q000187:drug effects / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D000076250:Myristoylated Alanine-Rich C Kinase Substrate; D009447:Neuroblastoma; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D021381:Protein Transport; D011554:Pseudopodia / Q000187:drug effects / Q000378:metabolism*; D034622:RNA Interference; D015398:Signal Transduction; D013997:Time Factors; D054460:rho-Associated Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D000199:Actins; D047908:Intracellular Signaling Peptides and Proteins; C000619710:MARCKS protein, human; D008565:Membrane Proteins; D019269:Phosphatidylinositol 4,5-Diphosphate; D047428:Protein Kinase Inhibitors; D000076250:Myristoylated Alanine-Rich C Kinase Substrate; D007334:Insulin-Like Growth Factor I; D054460:rho-Associated Kinases; D011493:Protein Kinase C