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


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.


CONCLUSIONS
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.
Stawowy
Philipp
P
Department of Medicine-Cardiology, Deutsches Herzzentrum Berlin, Augustenburger Platz 1, D-13353 Berlin, Germany.
Margeta
Christian
C
Blaschke
Florian
F
Lindschau
Carsten
C
Spencer-Hänsch
Chantel
C
Leitges
Michael
M
Biagini
Giuseppe
G
Fleck
Eckart
E
Graf
Kristof
K
D000804:Angiotensin II / Q000378:metabolism*; D000818:Animals; D015153:Blotting, Western / Q000379:methods; D002448:Cell Adhesion; D021982:Cell-Matrix Junctions / Q000378:metabolism; D003094:Collagen / Q000378:metabolism; D004789:Enzyme Activation; D005455:Fluorescent Antibody Technique; D006333:Heart Failure / Q000378:metabolism* / Q000473:pathology; D019012:Integrin beta1 / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D023421:Models, Animal; D032383:Myocytes, Cardiac / Q000378:metabolism* / Q000473:pathology; D010766:Phosphorylation; D051381:Rats; D017207:Rats, Sprague-Dawley; D020257:Ventricular Remodeling
D019012:Integrin beta1; D000804:Angiotensin II; D003094:Collagen