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M. Srinivas, Y. Gao; Functional Expression of Cx50 in Mouse Lens Epithelial Cells . Invest. Ophthalmol. Vis. Sci. 2005;46(13):1851.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Previous studies indicate that Cx50 is essential for lens growth (e.g. White et al., J. Cell Biol. 143:815–825; Sellitto et al., IOVS 45:3196–202). However, it is not known if Cx50 forms functional gap junction channels in lens epithelial cells. Electrophysiological studies suggest lens epithelial cells primarily express Cx43. In this study, we demonstrate that lens epithelial cells functionally express Cx50 gap junction channels by using quinine that was previously shown to block Cx50 gap junction channels without significantly affecting channels formed by the other two lens connexins, Cx43 and Cx46. Methods: Lens epithelial cells were acutely dissociated from postnatal day 3 (P3) mouse lenses and cultured in the presence of 2% fetal bovine serum and antibiotics. After 5–6 hrs, junctional currents between pairs of epithelial cells were measured using the dual whole cell patch clamp technique. Quinine (300 µM)was used to selectively block Cx50 gap junction channels. We previously showed that 300µM has little effect on Cx43 and Cx46 gap junction channels but blocks Cx50 junctional currents by ∼90% (Proc Natl Acad Sci U S A. 98:10942–7) Results: Junctional conductance in lens epithelial cells ranged from 0 nS to 5 nS. Exposure of epithelial cell pairs to 300 µM quinine caused a significant reduction in the junctional current by 46 ± 5 % (n=7), suggesting that Cx50 is functionally expressed between these cells. Measurement of single channel conductance in weakly coupled pairs provided additional evidence for the expression of Cx50. Histograms of channel conductances in weakly coupled pairs showed a distinct peak at 209 pS. This value is close to the unitary conductances of Cx50 homotypic gap junction channels in exogenously transfected cells. A scond peak at 110 pS, presumably corresponding to unitary conductance of Cx43 gap junction channels, was also observed. Conclusions: Our results indicate that Cx50 is co–expressed with Cx43 in epithelial cells during the first postnatal week, a period when the growth failure in knockouts is manifested. The mechanism by which Cx50 affects growth remains to be investigated.
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