Calpain Cleaves RhoA Generating a Dominant-negative Form That Inhibits Integrin-induced Actin Filament Assembly and Cell Spreading

Abstract

Integrin-induced cell adhesion results in transmission of signals that induce cytoskeletal reorganizations and resulting changes in cell behavior. The cytoskeletal reorganizations are regulated by transient activation and inactivation of Rho GTPases. Previously, we identified -calpain as an enzyme that is activated by signaling across ␤ 1 and ␤ 3 integrins. We showed that it mediates cytoskeletal reorganizations in bovine aortic endothelial (BAE) and Chinese hamster ovary (CHO) cells and does so by acting upstream of Rac1 activation. Here we show that -calpain is also involved in inactivating RhoA during integrin-induced signaling. Cleavage of RhoA was detectable in BAE cells plated on an integrin substrate; it did not occur in cells plated on poly-L-lysine. Cleavage was inhibited by calpain inhibitors. In vitro, -calpain cleaved RhoA generating a fragment of the same size as in intact cells. The cleavage site was identified, an HA-tagged construct expressing calpaincleaved RhoA generated, and the construct expressed in BAE and CHO cells. Calpain-cleaved RhoA inhibited integrin-induced stress fiber assembly and decreased cell spreading. Together, our data show that calpain cleaves RhoA and generates a form that inhibits integrin-induced stress fiber assembly and cell spreading.

Homocysteine enhances cardiac neural crest cell attachment in vitro by increasing intracellular calcium levels

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Rho GTPases in osteoclasts: Orchestrators of podosome arrangement

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Regulating cell migration: calpains make the cut

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