Journal
JOURNAL OF CELL BIOLOGY
Volume 158, Issue 2, Pages 357-369Publisher
ROCKEFELLER UNIV PRESS
DOI: 10.1083/jcb.200111028
Keywords
integrin; actin; Rac; ROS; mitochondria
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Funding
- NCI NIH HHS [P01 CA072006, CA 72006] Funding Source: Medline
- NIAMS NIH HHS [AR 20684] Funding Source: Medline
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We show here the transient activation of the small GTPase Rac, followed by a rise in reactive oxygen species (ROS), as necessary early steps in a signal transduction cascade that lead to NFkappaB activation and collagenase-1 (CL-1)/matrix metalloproteinase-1 production after integrin-mediated cell shape changes. We show evidence indicating that this constitutes a new mechanism for ROS production mediated by small GTPases. Activated RhoA also induced ROS production and up-regulated CL-1 expression. A Rac mutant (L37) that prevents reorganization of the actin cytoskeleton prevented integrin-induced CL-1 expression, whereas mutations that abrogate Rac binding to the neutrophil NADPH membrane oxidase in vitro (H26 and N130) did not. Instead, ROS were produced by integrin-induced changes in mitochondrial function, which were inhibited by Bcl-2 and involved transient membrane potential loss. The cells showing this transient decrease in mitochondrial membrane potential were already committed to CL-1 expression. These results unveil a new molecular mechanism of signal transduction triggered by integrin engagement where a global mitochondrial metabolic response leads to gene expression rather than apoptosis.
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