The Integrin-Linked Kinase-PINCH-Parvin Complex Supports Integrin alpha IIb beta 3 Activation

作者：Honda Shigenori^*; Shirotani Ikejima Hiroko; Tadokoro Seiji; Tomiyama Yoshiaki; Miyata Toshiyuki

来源：PLos One, 2013, 8(12): e85498.

DOI：10.1371/journal.pone.0085498

Integrin-linked kinase (ILK) is an important signaling regulator that assembles into the heteroternary complex with adaptor proteins PINCH and parvin (termed the IPP complex). We recently reported that ILK is important for integrin activation in a Chinese hamster ovary (CHO) cell system. We previously established parental CHO cells expressing a constitutively active chimeric integrin (alpha IIb alpha 6B beta 3) and mutant CHO cells expressing inactive alpha IIb alpha 6B beta 3 due to ILK deficiency. In this study, we further investigated the underlying mechanisms for ILK-dependent integrin activation. ILK-deficient mutant cells had trace levels of PINCH and alpha-parvin, and transfection of ILK cDNA into the mutant cells increased not only ILK but also PINCH and alpha-parvin, resulting in the restoration of alpha IIb alpha 6B beta 3 activation. In the parental cells expressing active alpha IIb alpha 6B beta 3, ILK, PINCH, and alpha-parvin were co-immunoprecipitated, indicating the formation of the IPP complex. Moreover, short interfering RNA (siRNA) experiments targeting PINCH-1 or both alpha- and beta-parvin mRNA in the parent cells impaired the alpha IIb alpha 6B beta 3 activation as well as the expression of the other components of the IPP complex. In addition, ILK mutants possessing defects in either PINCH or parvin binding failed to restore alpha IIb alpha 6B beta 3 activation in the mutant cells. Kindlin-2 siRNA in the parental cells impaired alpha IIb alpha 6B beta 3 activation without disturbing the expression of ILK. For CHO cells stably expressing wild-type alpha IIb alpha 6B beta 3 that is an inactive form, overexpression of a talin head domain (THD) induced alpha IIb beta 3 activation and the THD-induced alpha IIb alpha 6B beta 3 activation was impaired by ILK siRNA through a significant reduction in the expression of the IPP complex. In contrast, overexpression of all IPP components in the alpha IIb alpha 6B beta 3-expressing CHO cells further augmented THD-induced alpha IIb beta 3 activation, whereas they did not induce alpha IIb alpha 6B beta 3 activation without THD. These data suggest that the IPP complex rather than ILK plays an important role and supports integrin activation probably through stabilization of the active conformation.

• 出版日期2013-12-23