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A tyrosine-based sorting signal is involved in connexin43 stability and gap junction turnover |
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Published in | Journal of cell science. 2003, vol. 116, no. Pt 11, p. 2213-22 | |
Abstract | The gap junction protein connexin43 is known to have a rapid turnover, involving degradation by both the proteasomal and lysosomal systems, but the structural features of connexin43 that govern these actions are not known. The connexin43 C-terminal sequence contains a proline-rich region corresponding to the consensus of a protein-protein interaction PY-motif (xPPxY), and an overlapping putative tyrosine-based sorting signal (Yxxphi; =hydrophobic), known to play a role in the intracellular trafficking of many membrane proteins. As both motifs may control turnover of connexin43, we used a combination of metabolic radiolabelling, immuno-precipitation and functional assays to determine the possible role of these motifs in controlling degradation of human connexin43 expressed in SKHep1 cells. Mutation V289D in the tyrosine-based sorting motif increased the steady-state pool of connexin43 by approximately 3.5-fold, while mutation P283L in the PY-motif produced a comparatively modest augmentation (1.7-fold). No additive effect was observed when the overlapping tyrosine was mutated. In pulse-chase experiments, the Y286A substitution increased the half-life of connexin43 from 2 to 6 hours, indicating that the increased steady-state levels reflected reduced protein degradation. Moreover, expression at the junctional membrane, as well as gap junction-mediated intercellular communication (GJC), were nearly abolished by lysosomal inhibitors and Brefeldin A in cells expressing wild-type connexin43, but were unaffected in the tyrosine mutant. These results provide strong evidence that the tyrosine-based motif of human connexin43 is a prime determinant controlling connexin43 stability, and consequently GJC, by targeting connexin43 for degradation in the endocytic/lysosomal compartment. | |
Keywords | Carcinoma, Hepatocellular — Cell Line, Tumor — Connexin 43/genetics/metabolism — Cysteine Endopeptidases/metabolism — Endosomes/metabolism — Gap Junctions/metabolism — Humans — Liver Neoplasms — Lysosomes/metabolism — Multienzyme Complexes/metabolism — Mutagenesis/physiology — Proteasome Endopeptidase Complex — Protein Sorting Signals/physiology — Protein Transport/physiology — Tyrosine/metabolism | |
Identifiers | DOI: 10.1242/jcs.00440 PMID: 12730291 | |
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Structures | ||
Research group | Mucoviscidose et jonctions GAP (229) | |
Citation (ISO format) | THOMAS, Marc et al. A tyrosine-based sorting signal is involved in connexin43 stability and gap junction turnover. In: Journal of cell science, 2003, vol. 116, n° Pt 11, p. 2213-22. doi: 10.1242/jcs.00440 https://archive-ouverte.unige.ch/unige:27056 |