Manohar Asha, Shome Swati Ghosh, Lamar John, Stirling Lee, Iyer Vandana, Pumiglia Kevin, DiPersio C Michael
Center for Cell Biology and Cancer Research, Albany Medical College, MC-165, 47 New Scotland Avenue, Albany, New York, NY 12208, USA.
J Cell Sci. 2004 Aug 15;117(Pt 18):4043-54. doi: 10.1242/jcs.01277. Epub 2004 Jul 27.
Inadequate or inappropriate adhesion of epithelial cells to extracellular matrix leads to a form of apoptosis known as anoikis. During various tissue remodelling events, such as wound healing or carcinoma invasion, changes in the physical properties, and/or composition of the extracellular matrix, can lead to anoikis of epithelial cells that lack appropriate receptor-matrix interactions. Laminin-5 is the major ligand for keratinocyte adhesion in the epidermis, and it also promotes keratinocyte survival in vivo and in vitro. Integrins alpha 3 beta 1 and alpha 6 beta 4 are the major receptors for laminin-5; however, specific roles for these integrins in keratinocyte survival have not been determined. In the current study, we exploited keratinocyte cell lines derived from wild-type or alpha 3 integrin knockout mice to reveal a critical role for alpha 3 beta 1 in protecting keratinocytes from apoptosis upon serum withdrawal. We show that alpha 3 beta 1-mediated adhesion to laminin-5 extracellular matrix inhibits proteolytic activation of caspase-3 and TUNEL-staining, both hallmarks of apoptosis. We also show that alpha 3 beta1-mediated adhesion activates focal adhesion kinase (FAK) and extracellular signal-regulated kinase (ERK), and that inhibition of either FAK or ERK signaling leads to apoptosis of keratinocytes attached to laminin-5. alpha 6 beta 4-mediated adhesion to laminin-5 only partially protects cells from apoptosis in the absence of alpha 3 beta 1, and alpha 6 beta 4 is not necessary for cell survival in the presence of alpha 3 beta 1. These results suggest that alpha 3 beta 1 is necessary and sufficient for maximal keratinocyte survival on laminin-5. We propose a model to address the potential importance of alpha 3 beta 1-mediated survival for migrating keratinocytes at the leading edge of a cutaneous wound.
上皮细胞与细胞外基质的黏附不足或不适当会导致一种称为失巢凋亡的细胞凋亡形式。在各种组织重塑事件中，如伤口愈合或癌侵袭，细胞外基质的物理性质和/或组成的变化，可导致缺乏适当受体-基质相互作用的上皮细胞发生失巢凋亡。层粘连蛋白-5是表皮中角质形成细胞黏附的主要配体，它还能在体内和体外促进角质形成细胞的存活。整合素α3β1和α6β4是层粘连蛋白-5的主要受体；然而，这些整合素在角质形成细胞存活中的具体作用尚未确定。在本研究中，我们利用来自野生型或α3整合素基因敲除小鼠的角质形成细胞系，揭示了α3β1在血清撤出后保护角质形成细胞免于凋亡中的关键作用。我们发现，α3β1介导的与层粘连蛋白-5细胞外基质的黏附可抑制半胱天冬酶-3的蛋白水解激活和TUNEL染色，这两者都是细胞凋亡的标志。我们还发现，α3β1介导的黏附激活了黏着斑激酶（FAK）和细胞外信号调节激酶（ERK），并且抑制FAK或ERK信号传导会导致附着在层粘连蛋白-5上的角质形成细胞凋亡。在缺乏α3β1的情况下，α6β4介导的与层粘连蛋白-5的黏附仅能部分保护细胞免于凋亡，而在存在α3β1时，α6β4对细胞存活并非必需。这些结果表明，α3β1对于角质形成细胞在层粘连蛋白-5上的最大存活是必要且充分的。我们提出了一个模型，以探讨α3β1介导的存活对于皮肤伤口前沿迁移的角质形成细胞的潜在重要性。
