Repetitive Deformation Activates Focal Adhesion Kinase and ERK Mitogenic Signals in Human Caco-2 Intestinal Epithelial Cells through Src and Rac1

• Published in: The Journal of biological chemistry Vol. 282; no. 1; pp. 14 - 28
• Main Authors: Chaturvedi, Lakshmi S., Marsh, H. Michael, Shang, Xun, Zheng, Yi, Basson, Marc D.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 05.01.2007; American Society for Biochemistry and Molecular Biology
• Subjects: Animals; Caco-2 Cells; Epithelial Cells - cytology; Extracellular Signal-Regulated MAP Kinases - metabolism; Focal Adhesion Protein-Tyrosine Kinases - metabolism; Focal Adhesion Protein-Tyrosine Kinases - physiology; Humans; Intestinal Mucosa - metabolism; Models, Biological; Mucous Membrane - pathology; Mutation; Phosphorylation; rac1 GTP-Binding Protein - physiology; Rats; Signal Transduction; src-Family Kinases - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M605817200

Intestinal epithelial cells are subject to repetitive deformation during peristalsis and villous motility, whereas the mucosa atrophies during sepsis or ileus when such stimuli are abnormal. Such repetitive deformation stimulates intestinal epithelial proliferation via focal adhesion kinase (FAK) and extracellular signal-regulated kinases (ERK). However, the upstream mediators of these effects are unknown. We investigated whether Src and Rac1 mediate deformation-induced FAK and ERK phosphorylation and proliferation in human Caco-2 and rat IEC-6 intestinal epithelial cells. Cells cultured on collagen-I were subjected to an average 10% cyclic strain at 10 cycles/min. Cyclic strain activated Rac1 and induced Rac1 translocation to cell membranes. Mechanical strain also induced rapid sustained phosphorylation of c-Src at Tyr418, Rac1 at Ser71, FAK at Tyr397 and Tyr576, and ERK1/2 at Thr202/Tyr204. The mitogenic effect of cyclic strain was blocked by inhibition of Src (PP2 or short interfering RNA) or Rac1 (NSC23766). Src or Rac1 inhibition also prevented strain-induced FAK phosphorylation at Tyr576 and ERK phosphorylation but not FAK phosphorylation at Tyr397. Reducing FAK using short interfering RNA blocked strain-induced mitogenicity and attenuated ERK phosphorylation but not Src or Rac1 phosphorylation. Src inhibition blocked strain-induced Rac1 phosphorylation, but Rac inhibition did not alter Src phosphorylation. Transfection of a two-tyrosine phosphorylation-deficient FAK mutant Y576F/Y577F prevented activation of cotransfected myc-ERK2 by cyclic strain. Repetitive deformation induced by peristalsis or villus motility may support the gut mucosa by a pathway involving Src, Rac1, FAK, and ERK. This pathway may present important targets for interventions to prevent mucosal atrophy during prolonged ileus or fasting.