Cx43, ZO-1, alpha-catenin and beta-catenin in cataractous lens epithelial cells

Abstract

Specimens of the anterior lens capsule with an attached monolayer of lens epithelial cells (LECs) were obtained from patients (n=52) undergoing cataract surgery. Specimens were divided into three groups based on the type of cataract: nuclear cataract, cortical cataract and posterior subcapsular cataract (PSC). Clear lenses (n=11) obtained from donor eyes were used as controls. Expression was studied by immunofluorescence, real-time PCR and Western blot. Statistical analysis was done using the student's t-test. Immunofluorescence results showed punctate localization of Cx43 at the cell boundaries in controls, nuclear cataract and PSC groups. In the cortical cataract group, cytoplasmic pools of Cx43 without any localization at the cell boundaries were observed. Real-time PCR results showed significant up-regulation of Cx43 in nuclear and cortical cataract groups. Western blot results revealed significant increase in protein levels of Cx43 and significant decrease of ZO-1 in all three cataract groups. Protein levels of alpha-catenin were decreased significantly in nuclear and cortical cataract group. There was no significant change in expression of beta-catenin in the cataractous groups. Our findings suggest that ZO-1 and alpha-catenin are important for gap junctions containing Cx43 in the LECs. Alterations in cell junction proteins may play a role during formation of different types of cataract.

Regulation of Cellular Communication by Signaling Microdomains in the Blood Vessel Wall

“…These interactions have been extensively studied and shown by numerous biochemical techniques such as coimmunoprecipitation, immunofluorescence, proximity ligation assay, nuclear magnetic resonance, peptide competition, and pull-down assays (Toyofuku et al, 1998(Toyofuku et al, , 2001Kausalya et al, 2001;Sorgen et al, 2004a;Laing et al, 2005a,b;Bouvier et al, 2008;Chen et al, 2008;O'Quinn et al, 2011;Tence et al, 2012). The interaction between Cx43 and ZO-1 is not required for proper gap junction channel functionality per se but instead appears to negatively regulate accumulation of gap junction channels at the plasma membrane, limiting plaque size and stability (Giepmans, 2004(Giepmans, , 2006Hunter et al, 2005;Rhett et al, 2011;Arora et al, 2012). Plaque size is regulated by this interaction in two main ways: 1) by limiting incorporation of connexins into gap junction plaques and 2) by promoting endocytosis of connexins from gap junction plaques (Palatinus et al, 2012).…”

Defect of LSS Disrupts Lens Development in Cataractogenesis

“…At the equator plane, irregular size and swollen shape of fiber cells with plenty of nuclei were in the lens of Lss G589S/G589S homozygous mice, while uniform size and round shape of fiber cells with a few nuclei were in the lens of WT and Lss G589S/+ heterozygous mice ( Figure 8A ). ZO-1, a tight-junction protein, has been reported to localize in the apical membrane of lens epithelial cells (indicated as the EFI) during the lens development stage ( Nielsen et al, 2003 ; Wiley et al, 2010 ; Arora et al, 2012 ). In WT and heterozygous lenses at E14.5, ZO-1 was mainly expressed at the apical ends of the lens epithelial layer and prominently expressed at the lens fulcrum close to the equator ( Figure 8B , red arrows).…”

Bi-allelic Loss-of-Function Variants in DNMBP Cause Infantile Cataracts

“…Interestingly, a cohort of 52 individuals with cataracts has been reported to have remarkably reduced amounts of TJP1 in lens epithelial cells, suggesting that these junctions might play an important role in lens formation. 57 Moreover, DNMBP is a scaffold protein that interacts with dynamin to regulate the actin cytoskeleton. 42 It is well known that a sophisticated cytoskeleton network within lens fiber cells is crucial for their proper migration, elongation, and differentiation, as well as lens fiber maintenance.…”