An aberrant sequence in a connexin46 mutant underlies congenital cataracts

J Biol Chem. 2005 Dec 9;280(49):40788-95. doi: 10.1074/jbc.M504765200. Epub 2005 Oct 3.

Abstract

An increasing number of diseases have been mapped to genes coding for ion channel proteins, including the gap junction proteins, connexins. Here, we report on the identification of an amino acid sequence underlying the behavior of a non-functional mutant connexin46 (CX46) associated with congenital cataracts. The mutant protein, CX46fs380, is 31 amino acids longer than CX46 and contains 87 aberrant amino acids in its C terminus. When expressed in mammalian cells, the mutant CX46 was not found at gap junctional plaques, but it showed extensive co-localization with markers for ERGIC and Golgi. The severe reductions in function and formation of gap junctional plaques were transferred to other connexins by creating chimeras containing the last third (or more) of the aberrant C terminus of the CX46 mutant. This sequence also impaired trafficking of a CD8 chimera. Site-directed mutagenesis of a diphenylalanine restored appositional membrane localization and function. These results suggest a novel mechanism in which a mutation causes disease by generating a motif that leads to retention within the synthetic/secretory pathway.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Brefeldin A / pharmacology
  • Cataract / congenital*
  • Cataract / genetics*
  • Cell Membrane / chemistry
  • Connexins / chemistry*
  • Connexins / genetics*
  • Connexins / physiology
  • Cycloheximide / pharmacology
  • Electric Conductivity
  • Flow Cytometry
  • Fluorescent Antibody Technique
  • Gap Junctions / physiology
  • Gene Expression
  • HeLa Cells
  • Humans
  • Mice
  • Molecular Sequence Data
  • Mutation*
  • Oocytes / physiology
  • Protein Synthesis Inhibitors / pharmacology
  • Recombinant Fusion Proteins / analysis
  • Structure-Activity Relationship
  • Transfection
  • Xenopus

Substances

  • Connexins
  • Protein Synthesis Inhibitors
  • Recombinant Fusion Proteins
  • GJA3 protein, human
  • Brefeldin A
  • Cycloheximide