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Cataract-associated D3Y mutation of human connexin46 (hCx46) increases the dye coupling of gap junction channels and suppresses the voltage sensitivity of hemichannels.
MedLine Citation:
PMID:  22843197     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Connexin46 (Cx46), together with Cx50, forms gap junction channels between lens fibers and participates in the lens pump-leak system, which is essential for the homeostasis of this avascular organ. Mutations in Cx50 and Cx46 correlate with cataracts, but the functional relationship between the mutations and cataract formation is not always clear. Recently, it was found that a mutation at the third position of hCx46 that substituted an aspartic acid residue with a tyrosine residue (hCx46D3Y) caused an autosomal dominant zonular pulverulent cataract. We expressed EGFP-labeled hCx46wt and hCx46D3Y in HeLa cells and found that the mutation did not affect the formation of gap junction plaques. Dye transfer experiments using Lucifer Yellow (LY) and ethidium bromide (EthBr) showed an increased degree of dye coupling between the cell pairs expressing hCx46D3Y in comparison to the cell pairs expressing hCx46wt. In Xenopus oocytes, two-electrode voltage-clamp experiments revealed that hCx46wt formed voltage-sensitive hemichannels. This was not observed in the oocytes expressing hCx46D3Y. The replacement of the aspartic acid residue at the third position by another negatively charged residue, glutamic acid, to generate the mutant hCx46D3E, restored the voltage sensitivity of the resultant hemichannels. Moreover, HeLa cell pairs expressing hCx46D3E and hCx46wt showed a similar degree of dye coupling. These results indicate that the negatively charged aspartic acid residue at the third position of the N-terminus of hCx46 could be involved in the determination of the degree of metabolite cell-to-cell coupling and is essential for the voltage sensitivity of the hCx46 hemichannels.
Authors:
Barbara Schlingmann; Patrik Schadzek; Stefan Busko; Alexander Heisterkamp; Anaclet Ngezahayo
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-7-28
Journal Detail:
Title:  Journal of bioenergetics and biomembranes     Volume:  -     ISSN:  1573-6881     ISO Abbreviation:  -     Publication Date:  2012 Jul 
Date Detail:
Created Date:  2012-7-30     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  7701859     Medline TA:  J Bioenerg Biomembr     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Affiliation:
Institute of Biophysics, Leibniz University Hannover, Herrenhäuserstr. 2, 30419, Hannover, Germany.
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