富含半胱氨酸的蛋白61和结缔组织生长因子诱导视网膜周细胞脱黏附及失巢凋亡。

Cysteine-rich protein 61 and connective tissue growth factor induce deadhesion and anoikis of retinal pericytes.

作者信息

Liu Haibo, Yang Ru, Tinner Babben, Choudhry Annam, Schutze Norbert, Chaqour Brahim

机构信息

Department of Anatomy and Cell Biology, State University of New York Downstate Medical Center, Brooklyn, NY 11203, USA.

出版信息

Endocrinology. 2008 Apr;149(4):1666-77. doi: 10.1210/en.2007-1415. Epub 2008 Jan 10.

Abstract

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.

摘要

视网膜周细胞的丢失是糖尿病视网膜病变(DR)的显著特征之一,其特点是视网膜毛细血管闭塞。基质细胞蛋白富含半胱氨酸蛋白61(Cyr61)和结缔组织生长因子(CTGF)在DR早期阶段的视网膜血管系统中异常表达,但其对视网膜周细胞的影响尚不清楚。我们在此表明,暴露于晚期糖基化终产物(糖尿病的一种重要损伤刺激物)的大鼠视网膜周细胞(RRP),Cyr61和CTGF的表达水平均升高,并同时经历失巢凋亡,这是一种因细胞与基质相互作用丧失而导致的凋亡形式。腺病毒介导的Cyr61和/或CTGF表达赋予大鼠视网膜周细胞易发生失巢凋亡的表型,包括粘着斑处磷酸化酪氨酸蛋白水平降低以及形成皮质肌动蛋白环。当用作周细胞附着的底物并与其他基质蛋白(如IV型胶原)比较时,重组Cyr61和CTGF蛋白表现出抗粘附和促凋亡活性。磷酸酶抑制剂可逆转这些作用,表明Cyr61和CTGF促进去磷酸化事件。此外,Cyr61和CTGF诱导的凋亡是通过内在途径介导的,并且涉及功能上归类为p53靶基因的基因表达。基质金属蛋白酶-2基因(已知的p53靶标)在过表达Cyr61或CTGF的周细胞中表达增加。抑制基质金属蛋白酶-2至少部分地对Cyr61和CTGF诱导的凋亡具有保护作用。综上所述,这些发现支持Cyr61和CTGF参与周细胞脱离和失巢凋亡,提示这些蛋白参与DR的发病机制。

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