Eps8(EGF receptor pathway substrate NO.8)是受到EGFR與Src調控的一個受質，具有97KDa及68KDa兩種isoforms。先前實驗室發現v-Src transformed cell (IV5)中，Eps8的表現量及tyrosine phosphorylaton的情形均有增加的現象，而由許多的研究也發現（1）p97Eps8會去結合到integrin β-subunit的cytoplasmic domain；（2）Eps8可能會參與Ras調控Rac的活化這條訊息傳導路徑；（3）此外也證明v-Src會增加細胞的移動力。因此我們想更進一步去研究Eps8在v-Src所調控的細胞移動中扮演什麼角色。首先我們利用siRNA的技術去建立表達不同量Eps8的IV5細胞株。然後以Time-lapse video microscope去分析這些細胞株的細胞移動情形。根據我們所得到的實驗數據發現IV5 細胞中，v-Src可以促進細胞的移動，而這種增加的情形會因為細胞表現會降低p97Eps8與p68Eps8的eps8 siRNA，及專一降低p68Eps8的p68eps8 siRNA而遭到抑制；但若細胞表現只會降低p97Eps8的p97eps8 siRNA則看不到這種現象。進一步分析發現這是因為當細胞內的p97Eps8 與p68Eps8同時降低，會使得FAK tyrosine 576的磷酸化受到抑制，進而造成FAK的結合蛋白paxillin的磷酸化降低。這些實驗結果指出p97Eps8與p68Eps8可能透過改變FAK及paxillin的磷酸化，而共同參與在v-Src所促進的細胞移動訊息路徑中。

　　Previously, we have observed Eps8 (EGF receptor pathway substrate NO.8) is a common substrate of both EGFR and Src. And proteins with molecular weight of 97 and 68 kDa recognized by Eps8 antibodies have been referred to as the two isforms（p97Eps8 and p68Eps8）.Furthermore, both p97Eps8 and p68Eps8 expression is elevated in v-Src transformed cell IV5. Since 1) p97Eps8 may interact with the cytoplasmic domain of integrin β-subunit; 2) it participates in Ras-mediated Rac activation; and 3) v-Src could enhance cell motility, we wonder whether Eps8 may play a role in v-Src-mediated cell migration through interacting with these molecules. To address this issue, we utilize Time-lapse video microscope to analyze cell motility of IV5 cells expressing a variety of eps8 siRNA. Our data indicates that v-Src could increase cell motility of C3H10T1/2 and this enhancement is abrogated when both p97Eps8 and p68Eps8 expression is reduced by eps8 siRNA( specific small interference RNA), p68eps8 specific siRNA but not by p97eps8 specific siRNA. However, both p97Eps8 and p68Eps8 expression are reduced in p68eps8 siRNA overexpressing cells. Thus, p97Eps8 and p68Eps8 may cooperate in v-Src-mediated cell motility. Further studies indicated that phosphorylation of FAK Tyr-576 and paxillin is reduced when both p97Eps8 and p68Eps8 are knockdown. We conclude that both p97Eps8 and p68Eps8 could regulate FAK kinase activity through v-Src-mediated FAK Tyr-576 and paxillin phosphorylation and participate in the regulation of cell movement.

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