Matsuda Chie, Kameyama Kimihiko, Suzuki Atsushi, Mishima Wataru, Yamaji Satoshi, Okamoto Harumasa, Nishino Ichizo, Hayashi Yukiko K
Neuroscience Research Institute, AIST, Central 6, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8566, Japan.
FEBS Lett. 2008 Apr 9;582(8):1189-96. doi: 10.1016/j.febslet.2008.01.064. Epub 2008 Mar 4.
Affixin/beta-parvin is an integrin-linked kinase (ILK)-binding focal adhesion protein highly expressed in skeletal muscle and heart. To elucidate the possible role of affixin in skeletal muscle, we established stable C2C12 cell line expressing T7-tagged human affixin (C2C12-affixin cells). Exogenous expression of affixin promotes lamellipodium formation where affixin, ILK alphap21-activated kinase (PAK)-interactive exchange factor (PIX) and betaPIX accumulate. The association of affixin and betaPIX was confirmed by immunoprecipitation and pull down assay. In C2C12-affixin cells, an increased level of activated Rac1 but not Cdc42 was observed, and mutant betaPIX lacking guanine nucleotide exchange factor activity inhibited lamellipodium formation. These results suggest that affixin is involved in reorganization of subsarcolemmal cytoskeletal actin by activation of Rac1 through alpha and betaPIXs in skeletal muscle.
亲和素/β-帕文蛋白是一种与整合素连接激酶（ILK）结合的粘着斑蛋白，在骨骼肌和心脏中高表达。为了阐明亲和素在骨骼肌中的可能作用，我们建立了稳定表达T7标签人亲和素的C2C12细胞系（C2C12-亲和素细胞）。亲和素的外源表达促进片状伪足形成，亲和素、ILK、α21激活激酶（PAK）相互作用交换因子（PIX）和βPIX在片状伪足处聚集。通过免疫沉淀和下拉实验证实了亲和素与βPIX的结合。在C2C12-亲和素细胞中，观察到活性Rac1水平升高，但Cdc42未升高，缺乏鸟嘌呤核苷酸交换因子活性的突变型βPIX抑制了片状伪足的形成。这些结果表明，亲和素通过α和βPIX激活Rac1参与骨骼肌肌膜下细胞骨架肌动蛋白的重组。
