Selective activation of the Rac1/Cdc42 regulator beta-Pix governs cell migration in 3D collagen microenvironments

Wednesday, October 10, 2012 — Poster Session II
Noon – 2:00 p.m	Natcher Conference Center, Building 45	NIDCR	CELLBIO-7

* FARE Award Winner

Authors

• ML Kutys
• KM Yamada

Abstract

Cellular adhesion to the extracellular matrix (ECM) and subsequent migration are essential components of embryonic development, tissue repair, and immune response, and are often deregulated in atherosclerosis and cancer. However, the fundamental mechanisms that drive cellular migration in different ECM microenvironments are unknown. Using an affinity precipitation-based mass spectrometry screen to isolate active guanine-nucleotide exchange factors (GEFs), activators of the Rho GTPases, from human fibroblasts migrating in homogenous type I collagen, fibronectin, and ECM-free environments, we found that the Rac1/Cdc42 GEF beta-Pix was specifically and robustly activated during migration in collagen matrices. Assaying stable beta-Pix knockdown lines in different ECMs revealed that only in 3D collagen did knockdown inhibit cellular spreading and nearly abolish migration. This migratory defect is characterized by deregulated protrusions, impaired leading edge coordination, elevated contractility, and is governed by Cdc42 signaling. In contrast to fibronectin, live cell imaging reveals that beta-Pix does not localize to focal adhesions when on collagen, but instead accumulates on the membrane adjacent to areas of cellular protrusion, allowing for localized Cdc42 activation. These results establish ECM-dependent regulation of a specific GEF as a fundamental mechanism of migration in different microenvironments, and that beta-Pix is critical for cell migration in collagen environments.

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