Bouchard Véronique, Demers Marie-Josée, Thibodeau Sonya, Laquerre Vincent, Fujita Naoya, Tsuruo Takashi, Beaulieu Jean-François, Gauthier Rémy, Vézina Anne, Villeneuve Lisabeth, Vachon Pierre H
Département d'Anatomie et de Biologie Cellulaire, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Québec, Canada.
J Cell Physiol. 2007 Sep;212(3):717-28. doi: 10.1002/jcp.21096.
Human intestinal epithelial cell survival and anoikis are distinctively regulated according to the state of differentiation. In the present study, we analyzed the roles of focal adhesion kinase (Fak)/Src signaling to the PI3-K/Akt-1 and mitogen-activated protein kinase (MEK)/extracellular regulated kinases (Erk) pathways, within the context of such differentiation-state distinctions. Anoikis was induced by inhibition of beta1 integrins (antibody blocking), inhibition of Fak (pharmacologic inhibition or overexpression of dominant negative mutants), or by maintaining cells in suspension. Activation parameters of Fak, Src, Akt-1, and Erk1/2 were analyzed. Activities of Src, Akt-1, or Erk1/2 were also blocked by pharmacological inhibition or by overexpression of dominant-negative mutants. We report that: (1) the loss or inhibition of beta1 integrin binding activity causes anoikis and results in a down-activation of Fak, Src, Akt-1, and Erk1/2 in both undifferentiated, and differentiated cells; (2) the inhibition of Fak likewise causes anoikis and a down-activation of Src, Akt-1, and Erk1/2, regardless of the differentiation state; (3) Src, PI3-K/Akt-1, and MEK/Erk contribute to the survival of differentiated cells, whereas MEK/Erk does not play a role in the survival of undifferentiated ones; (4) the inhibition/loss of beta1 integrin binding and/or Fak activity results in a loss of Src engagement with Fak, regardless of the state of differentiation; and (5) Src contributes to the activation of both the PI3-K/Akt-1 and MEK/Erk pathways in undifferentiated cells, but does not influence PI3-K/Akt-1 in differentiated ones. Hence, Fak/Src signaling to the PI3-K/Akt-1 and MEK/Erk pathways undergoes a differentiation state-specific uncoupling which ultimately reflects upon the selective engagement of these same pathways in the mediation of intestinal epithelial cell survival.
人类肠道上皮细胞的存活和失巢凋亡根据分化状态受到不同调控。在本研究中，我们在这种分化状态差异的背景下，分析了粘着斑激酶（Fak）/Src信号传导对PI3-K/Akt-1和丝裂原活化蛋白激酶（MEK）/细胞外调节激酶（Erk）途径的作用。通过抑制β1整合素（抗体阻断）、抑制Fak（药理学抑制或显性负性突变体的过表达）或使细胞保持悬浮状态来诱导失巢凋亡。分析了Fak、Src、Akt-1和Erk1/2的激活参数。Src、Akt-1或Erk1/2的活性也通过药理学抑制或显性负性突变体的过表达而被阻断。我们报告如下：（1）β1整合素结合活性的丧失或抑制会导致失巢凋亡，并导致未分化和分化细胞中Fak、Src、Akt-1和Erk1/2的激活下调；（2）无论分化状态如何，Fak的抑制同样会导致失巢凋亡以及Src、Akt-1和Erk1/2的激活下调；（3）Src、PI3-K/Akt-1和MEK/Erk有助于分化细胞的存活，而MEK/Erk在未分化细胞的存活中不起作用；（4）β1整合素结合和/或Fak活性的抑制/丧失会导致Src与Fak的结合丧失，无论分化状态如何；（5）Src有助于未分化细胞中PI3-K/Akt-1和MEK/Erk途径的激活，但对分化细胞中的PI3-K/Akt-1没有影响。因此，Fak/Src向PI3-K/Akt-1和MEK/Erk途径的信号传导经历了分化状态特异性的解偶联，这最终反映在这些相同途径在介导肠道上皮细胞存活中的选择性参与上。
