MARCKS regulates lamellipodia formation induced by IGF‐I via association with PIP₂ and β‐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.

Fasudil inhibits lung carcinoma-conditioned endothelial cell viability and migration

“…Constitutively active RhoA can synergize with VEGF to stimulate angiogenesis (23), whereas dominant negative RhoA markedly inhibits VEGF-driven neovascularization (25). Thus, the function of RhoA is consistent with a possible role in vascular morphogenesis.…”

Myristoylated Alanine‐Rich Protein Kinase Substrate (MARCKS) Regulates Small GTPase Rac1 and Cdc42 Activity and Is a Critical Mediator of Vascular Smooth Muscle Cell Migration in Intimal Hyperplasia Formation

“…The small GTPases, Rac1 and Cdc42, are key regulators of cortical actin polymerization and are essential for lamellipodia and filopodia formation during cell migration 47. Depleting MARCKS impairs lamellipodia and filopodia formation, which has been well documented in both in vivo48 and in vitro cell‐culture systems 36, 49. However, the effect of MARCKS knockdown on Rac1 and Cdc42 has not been reported on.…”

Functional Role of the Interaction between Polysialic Acid and Myristoylated Alanine-rich C Kinase Substrate at the Plasma Membrane

“…In addition, MARCKS is involved in cell adhesion, lamellipodia formation, initiation of neuritogenesis, neurite outgrowth, growth cone adhesion, pathfinding, dendrite branching, dendritic spine morphogenesis, and synaptic plasticity (13,28,39,41,(61)(62)(63)(64)(65)(66)(67)(68)(69)(70)(71). Knockdown of MARCKS by RNA interference and overexpression of MARCKS mutants revealed that non-phosphorylated MARCKS stabilizes growth cone adhesion, enhances branching and growth of dendrites, elongates dendritic spines, and enhances initiation of neuritogenesis and neurite outgrowth (65,66,68,69).…”