Differential Phosphorylation of the Gap Junction Protein Connexin43 in Junctional Communication-Competent and -Deficient Cell Lines

• Published in: The Journal of cell biology Vol. 111; no. 5; pp. 2077 - 2088
• Main Authors: Musil, Linda S., Cunningham, Bruce A., Edelman, Gerald M., Goodenough, Daniel A.
• Format: Journal Article
• Language: English
• Published: New York, NY Rockefeller University Press 01.11.1990; The Rockefeller University Press
• Subjects: Analytical, structural and metabolic biochemistry; Animals; Biological and medical sciences; Cell Adhesion Molecules - physiology; Cell communication; Cell Communication - physiology; Cell culture techniques; Cell Line; Cell lines; Cells; Cellular immunity; Connexins; Epithelial cells; Fundamental and applied biological sciences. Psychology; Gap junctions; Hepatocytes; Intercellular Junctions - chemistry; Intercellular Junctions - physiology; Membrane Proteins - biosynthesis; Membrane Proteins - metabolism; Miscellaneous; Phosphorylation; Protein Processing, Post-Translational; Proteins; Transfection; Immunohistochemistry; Phosphorylation; Gel electrophoresis; Rodentia; Biosynthesis; Gap junction; Posttranslational modification; Proteins; Vertebrata; Immunoprecipitation reaction; Mammalia; Cell line; Localization; Pulse labelling
• ISSN: 0021-9525; 1540-8140
• DOI: 10.1083/jcb.111.5.2077

Connexin43 is a member of the highly homologous connexin family of gap junction proteins. We have studied how connexin monomers are assembled into functional gap junction plaques by examining the biosynthesis of connexin43 in cell types that differ greatly in their ability to form functional gap junctions. Using a combination of metabolic radiolabeling and immunoprecipitation, we have shown that connexin43 is synthesized in gap junctional communication-competent cells as a 42-kD protein that is efficiently converted to a ∼46-kD species (connexin43- P2) by the posttranslational addition of phosphate. Surprisingly, certain cell lines severely deficient in gap junctional communication and known cell-cell adhesion molecules (S180 and L929 cells) also expressed 42-kD connexin43. Connexin43 in these communication-deficient cell lines was not, however, phosphorylated to the P2 form. Conversion of S180 cells to a communication-competent phenotype by transfection with a cDNA encoding the cell-cell adhesion molecule L-CAM induced phosphorylation of connexin43 to the P2 form; conversely, blocking junctional communication in ordinarily communication-competent cells inhibited connexin43- P2 formation. Immunohistochemical localization studies indicated that only communication-competent cells accumulated connexin43 in visible gap junction plaques. Together, these results establish a strong correlation between the ability of cells to process connexin43 to the P2 form and to produce functional gap junctions. Connexin43 phosphorylation may therefore play a functional role in gap junction assembly and/or activity.