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Endocytosis and Endocytic Motifs across the Connexin Gene Family

Proteins fated to be internalized by clathrin-mediated endocytosis require an endocytic motif, where AP-2 or another adaptor protein can bind and recruit clathrin. Tyrosine and di-leucine-based sorting signals are such canonical motifs. Connexin 43 (Cx43) has three canonical tyrosine-based endocytic...

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Autores principales: Fisher, Charles G., Falk, Matthias M.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2023
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10454166/
https://www.ncbi.nlm.nih.gov/pubmed/37629031
http://dx.doi.org/10.3390/ijms241612851
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author Fisher, Charles G.
Falk, Matthias M.
author_facet Fisher, Charles G.
Falk, Matthias M.
author_sort Fisher, Charles G.
collection PubMed
description Proteins fated to be internalized by clathrin-mediated endocytosis require an endocytic motif, where AP-2 or another adaptor protein can bind and recruit clathrin. Tyrosine and di-leucine-based sorting signals are such canonical motifs. Connexin 43 (Cx43) has three canonical tyrosine-based endocytic motifs, two of which have been previously shown to recruit clathrin and mediate its endocytosis. In addition, di-leucine-based motifs have been characterized in the Cx32 C-terminal domain and shown to mediate its endocytosis. Here, we examined the amino acid sequences of all 21 human connexins to identify endocytic motifs across the connexin gene family. We find that although there is limited conservation of endocytic motifs between connexins, 14 of the 21 human connexins contain one or more canonical tyrosine or di-leucine-based endocytic motif in their C-terminal or intracellular loop domain. Three connexins contain non-canonical (modified) di-leucine motifs. However, four connexins (Cx25, Cx26, Cx31, and Cx40.1) do not harbor any recognizable endocytic motif. Interestingly, live cell time-lapse imaging of different GFP-tagged connexins that either contain or do not contain recognizable endocytic motifs readily undergo endocytosis, forming clearly identifiable annular gap junctions when expressed in HeLa cells. How connexins without defined endocytic motifs are endocytosed is currently not known. Our results demonstrate that an array of endocytic motifs exists in the connexin gene family. Further analysis will establish whether the sites we identified in this in silico analysis are legitimate endocytic motifs.
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spelling pubmed-104541662023-08-26 Endocytosis and Endocytic Motifs across the Connexin Gene Family Fisher, Charles G. Falk, Matthias M. Int J Mol Sci Article Proteins fated to be internalized by clathrin-mediated endocytosis require an endocytic motif, where AP-2 or another adaptor protein can bind and recruit clathrin. Tyrosine and di-leucine-based sorting signals are such canonical motifs. Connexin 43 (Cx43) has three canonical tyrosine-based endocytic motifs, two of which have been previously shown to recruit clathrin and mediate its endocytosis. In addition, di-leucine-based motifs have been characterized in the Cx32 C-terminal domain and shown to mediate its endocytosis. Here, we examined the amino acid sequences of all 21 human connexins to identify endocytic motifs across the connexin gene family. We find that although there is limited conservation of endocytic motifs between connexins, 14 of the 21 human connexins contain one or more canonical tyrosine or di-leucine-based endocytic motif in their C-terminal or intracellular loop domain. Three connexins contain non-canonical (modified) di-leucine motifs. However, four connexins (Cx25, Cx26, Cx31, and Cx40.1) do not harbor any recognizable endocytic motif. Interestingly, live cell time-lapse imaging of different GFP-tagged connexins that either contain or do not contain recognizable endocytic motifs readily undergo endocytosis, forming clearly identifiable annular gap junctions when expressed in HeLa cells. How connexins without defined endocytic motifs are endocytosed is currently not known. Our results demonstrate that an array of endocytic motifs exists in the connexin gene family. Further analysis will establish whether the sites we identified in this in silico analysis are legitimate endocytic motifs. MDPI 2023-08-16 /pmc/articles/PMC10454166/ /pubmed/37629031 http://dx.doi.org/10.3390/ijms241612851 Text en © 2023 by the authors. https://creativecommons.org/licenses/by/4.0/Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
spellingShingle Article
Fisher, Charles G.
Falk, Matthias M.
Endocytosis and Endocytic Motifs across the Connexin Gene Family
title Endocytosis and Endocytic Motifs across the Connexin Gene Family
title_full Endocytosis and Endocytic Motifs across the Connexin Gene Family
title_fullStr Endocytosis and Endocytic Motifs across the Connexin Gene Family
title_full_unstemmed Endocytosis and Endocytic Motifs across the Connexin Gene Family
title_short Endocytosis and Endocytic Motifs across the Connexin Gene Family
title_sort endocytosis and endocytic motifs across the connexin gene family
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10454166/
https://www.ncbi.nlm.nih.gov/pubmed/37629031
http://dx.doi.org/10.3390/ijms241612851
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