中文摘要

　　對於生物物理訊息如何調控一個細胞的行為仍是很少人瞭解，但是一個有趣的問題。我們將狗腎臟上皮細胞株-Madin-Darby canine kidney (MDCK) 培養在膠原蛋白凝膠、塗有膠原蛋白的培養皿以及一般的培養皿上來研究膠原蛋白纖維的軟硬如何影響細胞生理機能。我們發現膠原蛋白凝膠可以刺激細胞爬行並且有大量的ERK1/2磷酸化的現象產生，而且這樣磷酸化的情況可以維持到八個小時之久，此現象並未在於培養在塗有膠原蛋白的培養皿和培養皿的細胞上出現，由此可知，這種ERK1/2活化和細胞爬行的現象是由基質的軟硬不同所造成的。利用PD98059 和U0126 (MEK1 inhibitors)去抑制軟性基質所引發的ERK1/2磷酸化會造成細胞的伸展能力下降並且抑制細胞的爬行，但不影響細胞在塗有膠原蛋白的培養皿和培養皿的伸展。有趣的是，我們同時發現被磷酸化的ERK1/2可以表現在細胞核以及focal adhesion的位置。表示細胞可以藉由磷酸化的ERK出現在focal adhesion進而造成細胞伸展在軟性基質上。以lipid raft的抑制劑或是caveolin-1siRNA的實驗證明lipid raft是調控ERK1/2磷酸化的主要來源。總而言之，軟性基質可以誘發細胞中的ERK1/2磷酸化藉此促使細胞伸展和爬行於軟性質上，而這種ERK1/2磷酸化主要是從lipid raft來，而不是caveolae。

Abstract
　　How mechanical signals affect cell behaviors is a less studied issue. In this study, we cultured Madin-Darby canine kidney (MDCK) cells under different conditions, collagen gel, collagen gel-coated dish and dish, to investigate how rigidity of collagen fiber affected the cellular behaviors. I found that collagen gel induced cell migration and phosphorylation of ERK1/2 within 1 h and the induction could last for 8 h. Because collagen gel coating did not alter ERK 1/2 activity, collagen gel-induced cell migration and activation of ERK1/2 are mediated by physical property, i.e. rigidity. Inhibition of collagen gel-induced ERK1/2 phosphorylation by MEK inhibitors, PD98059 and U0126, resulted in cell round up and reduction of cell migration. Interestingly, the collagen gel-induced ERK1/2 phosphorylation was present in nuclei and focal adhesion site, indicating that ERK1/2 activation leads to cell spreading and migration. Moreover, filipin III, a lipid raft inhibitor, prevented low rigidity-induced ERK1/2 phosphorylation. On the other hand, caveolin-1 siRNA did not block low rigidity-induced cell round up. Taken together, low rigidity of collagen fiber induces activation of ERK1/2 which facilitates cell spreading and migration on collagen gel, which may be mediated by lipid raft, but not caveolae.

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