Evidence for the presence of a free C-terminal fragment of cx43 in cultured cells.
Migration of the gap junction protein connexin 43 (Cx43) in SDS-PAGE yields 2 to 4 distinct bands, detectable in the 40-47 kDa range. Here, we show that antibodies against the carboxy-terminal domain of Cx43 recognized an additional 20-kDa product. This protein was detected in some culture cell lysates. The presence of the 20-kDa band was not prevented by the use of protease inhibitors (Complete(R) and phenylmethylsulfonyl fluoride (PMSF), 1-5 mM). The band was absent from cells treated with Cx43-specific RNAi, and from those derived from Cx43-deficient mice, indicating that this Cx43-immunoreactive protein is a product of the Cx43 gene. Treatment of CHO cells with cyclosporin A caused a reduction in the amount of full-length Cx43 and a concomitant increase in the amount of the 20-kDa band. Overall, our data show that a fraction of the Cx43-immunoreactive protein pool within a given cell may correspond to a C-terminal fragment of the protein.
Department of Pharmacology, SUNY Upstate Medical University, Syracuse, New York 13210, USA.
Rosy
R
Joshi-Mukherjee
Wanda
W
Coombs
Christine
C
Burrer
Isabel Alvarez
IA
de Mora
Mario
M
Delmar
Steven M
SM
Taffet
D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D016466:CHO Cells; D002478:Cells, Cultured; D018031:Connexin 43 / Q000737:chemistry* / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D006224:Cricetinae; D003412:Cricetulus; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D051379:Mice; D018345:Mice, Knockout; D008970:Molecular Weight; D017830:Octoxynol / Q000494:pharmacology; D010446:Peptide Fragments / Q000737:chemistry* / Q000378:metabolism*; D011480:Protease Inhibitors / Q000494:pharmacology; D017434:Protein Structure, Tertiary; D034741:RNA, Small Interfering / Q000378:metabolism; D051381:Rats; D012995:Solubility / Q000187:drug effects; D013347:Subcellular Fractions / Q000187:drug effects
D000906:Antibodies; D018031:Connexin 43; D010446:Peptide Fragments; D011480:Protease Inhibitors; D034741:RNA, Small Interfering; D017830:Octoxynol