Studies on regulation of actin cytoskeleton by phosphatidylinositol-3 kinase and its application.

细胞运动通常是由细胞骨架重排引起的。我们发现SWAP-70作为一种调节肌动蛋白重排的蛋白，依赖于磷脂酰肌醇-3激酶参与了细胞膜的褶皱。SWAP-70与激活的RAC和F-肌动蛋白结合。从SWAP-70缺陷小鼠培养的肾细胞在EGF处理后表现出受损的膜褶皱。DEF-6是一种与SWAP-70同源的蛋白质，缺乏SWAP-70中发现的F-肌动蛋白结合位点。今年，我们探索了这两种蛋白质的差异。这两种蛋白质在Cos7细胞中过表达时促进了膜皱折，表明这两种蛋白质都参与了膜皱折。它们都与活化的RAC共定位，但表型有很大不同。SWAP-70诱导细胞膜皱缩，而Def-6诱导细胞明显畸形。时间推移实验表明，这种形态变化是可逆的，表明细胞正在迅速改变形状。这些结果表明，这两种蛋白质高度同源，但它们对膜褶皱的作用方式完全不同。讨论结合活动如何与它们的功能相关是很有趣的。

Cell motility is often caused by cytoskeletal rearrangement. We found SWAP-70 as a protein which regulates actin rearrangement depending on phosphatidylinositol-3 kinase to be involved in membrane ruffling. SWAP-70 binds to activated Rac and F-actin. Kidney cells cultured from SWAP-70 deficient mice exhibits impaired membrane ruffling after EGF treatment. Def-6, a protein homologous to SWAP-70 lacks the F-actin binding site found in SWAP-70. This year, we explored the difference of these two proteins.The two proteins enhanced membrane ruffling when overexpressed in Cos7 cells, suggesting that these proteins are both involved in membrane ruffling. They both co-localized with activated Rac, however, the phenotypes were quite different. SWAP-70 induced membrane ruffling but Def-6 induced marked misshaping of the cells. The time lapse experiment revealed that this morphological change was reversible, suggesting that cells are quickly changing their shapes. These results suggest that the two proteins are highly homologous but they contributes to membrane ruffling in completely different ways. It is interesting to argue how the binding activity correlates with their functions.