Oh Min-A, Choi Suyong, Lee Mi Ji, Choi Moon-Chang, Lee Sin-Ae, Ko Wonil, Cance William G, Oh Eok-Soo, Buday Laszlo, Kim Sung-Hoon, Lee Jung Weon
Cancer Research Institute, Cell Dynamics Research Center, Department of Tumor Biology, College of Medicine, Seoul National University, 101, Daehangro, Jongno-gu, Seoul 110-799, Republic of Korea.
Biochim Biophys Acta. 2009 May;1793(5):781-91. doi: 10.1016/j.bbamcr.2009.01.015. Epub 2009 Feb 5.
Cell adhesion to the extracellular matrix (ECM) can activate signaling via focal adhesion kinase (FAK) leading to dynamic regulation of cellular morphology. Mechanistic basis for the lack of effective intracellular signaling by non-attached epithelial cells is poorly understood. To examine whether signaling in suspended cells is regulated by Fer cytoplasmic tyrosine kinase, we investigated the effect of ectopic Fer expression on signaling in suspended or adherent hepatocytes. We found that ectopic Fer expression in Huh7 hepatocytes in suspension or on non-permissive poly-lysine caused significant phosphorylation of FAK Tyr577, Tyr861, or Tyr925, but not Tyr397 or Tyr576. Fer-mediated FAK phosphorylation in suspended cells was independent of c-Src activity or growth factor stimulation, but dependent of cortactin expression. Consistent with these results, complex formation between FAK, Fer, and cortactin was observed in suspended cells. The Fer-mediated effect correlated with multiple membrane protrusions, even on poly-lysine. Together, these observations suggest that Fer may allow a bypass of anchorage-dependency for intracellular signal transduction in hepatocytes.
细胞与细胞外基质（ECM）的黏附可通过黏着斑激酶（FAK）激活信号传导，从而导致细胞形态的动态调节。对于未附着的上皮细胞缺乏有效细胞内信号传导的机制基础，人们了解甚少。为了研究悬浮细胞中的信号传导是否受Fer细胞质酪氨酸激酶调节，我们研究了异位表达Fer对悬浮或贴壁肝细胞中信号传导的影响。我们发现，在悬浮的或在非允许性聚赖氨酸上的Huh7肝细胞中异位表达Fer会导致FAK的Tyr577、Tyr861或Tyr925发生显著磷酸化，但不会导致Tyr397或Tyr576磷酸化。悬浮细胞中Fer介导的FAK磷酸化与c-Src活性或生长因子刺激无关，但依赖于皮层肌动蛋白的表达。与这些结果一致，在悬浮细胞中观察到了FAK、Fer和皮层肌动蛋白之间的复合物形成。即使在聚赖氨酸上，Fer介导的效应也与多个膜突出相关。总之，这些观察结果表明，Fer可能允许肝细胞在细胞内信号转导中绕过对锚定的依赖性。
