Molecular mechanisms underlying enhanced hemichannel function of a cataract-associated Cx50 mutant.

Autor:	Tong JJ; Center of Proteomics and Molecular Therapeutics, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois., Khan U; Department of Chemistry, Portland State University, Portland, Oregon., Haddad BG; Department of Chemistry, Portland State University, Portland, Oregon., Minogue PJ; Department of Pediatrics, University of Chicago, Chicago, Illinois., Beyer EC; Department of Pediatrics, University of Chicago, Chicago, Illinois., Berthoud VM; Department of Pediatrics, University of Chicago, Chicago, Illinois., Reichow SL; Department of Chemistry, Portland State University, Portland, Oregon. Electronic address: reichow@pdx.edu., Ebihara L; Center of Proteomics and Molecular Therapeutics, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois; Discipline of Physiology and Biophysics, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois. Electronic address: lisa.ebihara@rosalindfranklin.edu.
Jazyk:	angličtina
Zdroj:	Biophysical journal [Biophys J] 2021 Dec 21; Vol. 120 (24), pp. 5644-5656. Date of Electronic Publication: 2021 Nov 09.
DOI:	10.1016/j.bpj.2021.11.004
Abstrakt:	Connexin-50 (Cx50) is among the most frequently mutated genes associated with congenital cataracts. Although most of these disease-linked variants cause loss of function because of misfolding or aberrant trafficking, others directly alter channel properties. The mechanistic bases for such functional defects are mostly unknown. We investigated the functional and structural properties of a cataract-linked mutant, Cx50T39R (T39R), in the Xenopus oocyte system. T39R exhibited greatly enhanced hemichannel currents with altered voltage-gating properties compared to Cx50 and induced cell death. Coexpression of mutant T39R with wild-type Cx50 (to mimic the heterozygous state) resulted in hemichannel currents whose properties were indistinguishable from those induced by T39R alone, suggesting that the mutant had a dominant effect. Furthermore, when T39R was coexpressed with Cx46, it produced hemichannels with increased activity, particularly at negative potentials, which could potentially contribute to its pathogenicity in the lens. In contrast, coexpression of wild-type Cx50 with Cx46 was associated with a marked reduction in hemichannel activity, indicating that it may have a protective effect. All-atom molecular dynamics simulations indicate that the R39 substitution can form multiple electrostatic salt-bridge interactions between neighboring subunits that could stabilize the open-state conformation of the N-terminal (NT) domain while also neutralizing the voltage-sensing residue D3 as well as residue E42, which participates in loop gating. Together, these results suggest T39R acts as a dominant gain-of-function mutation that produces leaky hemichannels that may cause cytotoxicity in the lens and lead to development of cataracts. (Copyright © 2021 Biophysical Society. Published by Elsevier Inc. All rights reserved.)
Databáze:	MEDLINE
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