title: The cataract causing Cx50-S50P mutant inhibits Cx43 and intercellular communication in the lens epithelium.
abstract: Mutations in Connexin50 (Cx50) cause cataracts in both humans and mice. The mechanism(s) behind how mutated connexins lead to a variety of cataracts have yet to be fully elucidated. Here, we tested whether the cataract inducing Cx50-S50P mutant interacts with wild-type Connexin43 (Cx43) to form mixed channels with attenuated function. Using dual whole-cell voltage clamp, immunofluorescent microscopy and in situ dye transfer analysis we identified a unique interaction between the mutant subunit and wild-type Cx43. In paired Xenopus oocytes, co-expression of Cx50-S50P with Cx43 reduced electrical coupling >/=90%, without a reduction in protein expression. In transfected cells, Cx50-S50P did not target to cell-cell interfaces by itself, but co-expression of Cx50-S50P with Cx43 resulted in its localization at areas of cell-cell contact. We used Cx43 conditional knockout, Cx50 knockout and Cx50-S50P mutant mice to examine this interaction in vivo. Mice expressing both Cx43 and Cx50-S50P in the lens epithelium revealed a unique expression pattern for Cx43 and a reduction in Cx43 protein. In situ dye transfer experiments showed that the Cx50-S50P mutant, but not the Cx50, or Cx43 conditional knockout, greatly inhibited epithelial cell gap junctional communication in a manner similar to a double knockout of Cx43 and Cx50. The inhibitory affects of Cx50-S50P lead to diminished electrical coupling in vitro, as well as a discernable reduction in epithelial cell dye permeation. These data suggest that dominant inhibition of Cx43 mediated epithelial cell coupling may play a role in the lens pathophysiology caused by the Cx50-S50P mutation.
authors.affiliation: Department of Physiology and Biophysics, State University of New York, T5-147, Basic Science Tower, Stony Brook, NY 11794-8661, USA.
authors.forename: Adam M
authors.initials: AM
authors.lastname: DeRosa
authors.forename: Gülistan
authors.initials: G
authors.lastname: Meşe
authors.forename: Leping
authors.initials: L
authors.lastname: Li
authors.forename: Caterina
authors.initials: C
authors.lastname: Sellitto
authors.forename: Peter R
authors.initials: PR
authors.lastname: Brink
authors.forename: Xiaohua
authors.initials: X
authors.lastname: Gong
authors.forename: Thomas W
authors.initials: TW
authors.lastname: White