Cysteine-rich protein 61 and connective tissue growth factor induce deadhesion and anoikis of retinal pericytes.
Loss of retinal pericytes is one of the distinctive features of diabetic retinopathy (DR), which is characterized by retinal capillary obliteration. The matricellular proteins, cysteine-rich protein 61 (Cyr61) and connective tissue growth factor (CTGF), are aberrantly expressed in the retinal vasculature from the early stages of DR, but their effects on retinal pericytes are unknown. We show herein that rat retinal pericytes (RRPs) exposed to advanced glycosylation-end products, an important injurious stimulus of diabetes, express increased levels of both Cyr61 and CTGF, and concomitantly undergo anoikis, a form of apoptosis by loss of cell-matrix interactions. Adenovirus-mediated expression of Cyr61 and/or CTGF conferred an anoikis-prone phenotype to rat retinal pericytes, including decreased phosphotyrosine protein levels at focal adhesion points and formation of cortical actin rings. When used as substrates for pericyte attachment and compared with other matrix proteins (e.g. type IV collagen), recombinant Cyr61 and CTGF proteins exhibited antiadhesive and apoptogenic activities. Phosphatase inhibitors reversed these effects, suggesting that Cyr61 and CTGF promote dephosphorylation events. Furthermore, Cyr61- and CTGF-induced apoptosis was mediated through the intrinsic pathway and involved the expression of genes that have been functionally grouped as p53 target genes. Expression of the matrix metalloproteinase-2 gene, a known target of p53, was increased in pericytes overexpressing either Cyr61 or CTGF. Inhibition of matrix metalloproteinase-2 had, at least in part, a protective effect against Cyr61- and CTGF-induced apoptosis. Taken together, these findings support the involvement of Cyr61 and CTGF in pericyte detachment and anoikis, implicating these proteins in the pathogenesis of DR.
Liu
Haibo
H
Department of Anatomy and Cell Biology, State University of New York Downstate Medical Center, Brooklyn, NY 11203, USA.
Yang
Ru
R
Tinner
Babben
B
Choudhry
Annam
A
Schutze
Norbert
N
Chaqour
Brahim
B
D000818:Animals; D023102:Anoikis; D017209:Apoptosis; D002448:Cell Adhesion; D002478:Cells, Cultured; D055513:Connective Tissue Growth Factor; D055515:Cysteine-Rich Protein 61; D003930:Diabetic Retinopathy / Q000209:etiology; D017874:Immediate-Early Proteins / Q000235:genetics / Q000502:physiology*; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000502:physiology*; D020778:Matrix Metalloproteinase 2 / Q000235:genetics; D020286:Pericytes / Q000473:pathology*; D010766:Phosphorylation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012160:Retina / Q000166:cytology*; D015398:Signal Transduction
C501849:CCN1 protein, rat; C526316:CCN2 protein, rat; D055515:Cysteine-Rich Protein 61; D017874:Immediate-Early Proteins; D036341:Intercellular Signaling Peptides and Proteins; D055513:Connective Tissue Growth Factor; D020778:Matrix Metalloproteinase 2