スフィンゴ脂質作用によるアクチン特殊構造形成の微細形態学的解析

抄録

We have been searching for mechanism to induce smooth muscle contraction migration that involved actin remodeling and associated with phosphorylation of Myosin light chain (MLC) of smooth muscle myosin. We report that Spingosylphosphorylcholine (SPC) stimulates ATPase activity of vascular smooth muscle (A7r5) cell and increased migration of A7r5 cells and enhanced appearance magnapodia consisting of actin membrane structure. After SPC stimulation, mitogen-activated protein kinases (MAPKs),inculuding p38 MAPK (p38) and p42/44 MAPK (p42/44) were found to phosphorylated. Migration of cells toward SPC was reduced in the presence of SB-203580, an inhibitor of p38, but not PD-98059, an inhibitor of p42/44, Pertussis toxin (PTX), aGi prptein inhibitor, induced an inhibitory effect on p38 phosphorylation and A7r5 cells migration. Myosin light chain (MLC) phosphorylation occurred after SPC stimulation with or without pretreatment with SB-203580 or PTX. The MLC kinase inhibitor ML-7 and the Rho kinase inhibitor Y-27632 inhibited MLC phosphorylation but only partially inhibited SPC-directed miglation. Complete inhibition was achieved with the addition of SB-203580. After SPC 1 mM stimulation, actin cytoskeleton formed thick bundles of actin filaments around the periphery of cells, and the cells were surrounded by elongated a– actin and b- actin, but magnapodia consisited exclusively of –actin. Such a remodeling of actin was reversed by addition of SB-203580 and PTX, but not ML-7 or Y-27632. Taken together, our biochemical and morphorogical data confirmed the regulation of actin remodeling and suggest that A7r5 cells migrate toward SPC, not only by an MLC phosphorylation-dependent pathway, but also by an MLC phosphorylation-independent pathway.