Protein kinase C epsilon mediates angiotensin II-induced activation of beta1-integrins in cardiac fibroblasts.

Abstract

OBJECTIVE:

Angiotensin II (AII) promotes cardiac fibrosis by increased extracellular matrix production and enhanced interaction of matrix proteins with their cellular receptors, including integrins. AII and other growth factors augment beta(1)-integrin-dependent adhesion and spreading by "inside-out signaling" without affecting the total number of integrin receptors. "Inside-out signaling" involves specific signaling pathways, including protein kinase C (PKC), leading to activation of beta1-integrins. In the present study we investigated the mechanisms involved in AII-increased adhesion of adult rat cardiac fibroblasts (CFBs), obtained from Sprague-Dawley rats, to collagen I mediated by beta1-integrin.

METHODS AND RESULTS:

Treatment of CFBs with AII induced a concentration-dependent increase in adhesion to collagen I (2.2-fold, p<0.01) within 3-6 h of treatment. This effect was mediated by beta1-integrin via the angiotensin AT1 receptor and was significantly reduced by protein kinase C inhibition. AII significantly induced phosphorylation of PKC epsilon (PKCepsilon), which is involved in beta1-integrin-dependent adhesion and motility, and phosphorylation of the cytoplasmatic tail of beta1-integrin at threonine 788/789, required for adhesion. Phosphorylation of beta1-integrin and an increase in adhesion was also induced by l-alpha-phosphatidylinositol-3,4,5-triphosphate (l-alpha-PIP3), an activator of endogenous PKCepsilon. AII failed to increase adhesion in myofibroblasts obtained from PKCepsilon (-/-) mice, but not in cells obtained from control mice. Co-immunoprecipitation and double immunofluorescence demonstrated that AII induced a close association of PKCepsilon with beta1-integrin in CFBs.

CONCLUSION:

The present study demonstrates that AII increased beta1-integrin-dependent adhesion to collagen I in cardiac fibroblasts by inside-out signaling via PKCepsilon and phosphorylation of the cytoplasmatic tail of the beta1-integrin.

• Authors: Philipp Stawowy, Christian Margeta, Florian Blaschke, Carsten Lindschau, Chantel Spencer-Hänsch, Michael Leitges, Giuseppe Biagini, Eckart Fleck, Kristof Graf
• Journal: Cardiovascular research (Cardiovasc Res) Vol. 67 Issue 1 Pg. 50-9 (Jul 01 2005) ISSN: 0008-6363 [Print] England
• PMID: 15949469 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Integrin beta1
• Angiotensin II
• Collagen

Topics

• Angiotensin II (metabolism)
• Animals
• Blotting, Western (methods)
• Cell Adhesion
• Cell-Matrix Junctions (metabolism)
• Collagen (metabolism)
• Enzyme Activation
• Fluorescent Antibody Technique
• Heart Failure (metabolism, pathology)
• Integrin beta1 (metabolism)
• Mice
• Mice, Knockout
• Models, Animal
• Myocytes, Cardiac (metabolism, pathology)
• Phosphorylation
• Rats
• Rats, Sprague-Dawley
• Ventricular Remodeling