Tyrosine phosphorylation of the gap junction protein connexin43 is required for the pp60v-src-induced inhibition of communication.
Gap junction communication in some cells has been shown to be inhibited by pp60v-src, a protein tyrosine kinase encoded by the viral oncogene v-src. The gap junction protein connexin43 (Cx43) has been shown to be phosphorylated on serine in the absence of pp60v-src and on both serine and tyrosine in cells expressing pp60v-src. However, it is not known if the effect of v-src expression on communication results directly from tyrosine phosphorylation of the Cx43 or indirectly, for example, by activation of other second-messenger systems. In addition, the effect of v-src expression on communication based on other connexins has not been examined. We have used a functional expression system consisting of paired Xenopus oocytes to examine the effect of v-src expression on the regulation of communication by gap junctions comprised of different connexins. Expression of pp60v-src completely blocked the communication induced by Cx43 but had only a modest effect on communication induced by connexin32 (Cx32). Phosphoamino acid analysis showed that pp60v-src induced tyrosine phosphorylation of Cx43, but not Cx32. A mutation replacing tyrosine 265 of Cx43 with phenylalanine abolished both the inhibition of communication and the tyrosine phosphorylation induced by pp60v-src without affecting the ability of this protein to form gap junctions. These data show that the effect of pp60v-src on gap junctional communication is connexin specific and that the inhibition of Cx43-mediated junctional communication by pp60v-src requires tyrosine phosphorylation of Cx43.
Swenson
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Department of Anatomy and Cellular Biology, Harvard Medical School, Boston, Massachusetts.
Piwnica-Worms
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McNamee
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Paul
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D000595:Amino Acid Sequence; D000818:Animals; D002450:Cell Communication / Q000502:physiology*; D002455:Cell Division / Q000502:physiology; D017630:Connexins; D015870:Gene Expression / Q000502:physiology; D008565:Membrane Proteins / Q000378:metabolism*; D008845:Microinjections; D008969:Molecular Sequence Data; D015688:Oncogene Protein pp60(v-src) / Q000378:metabolism*; D009865:Oocytes / Q000378:metabolism*; D010766:Phosphorylation; D012333:RNA, Messenger / Q000378:metabolism; D012694:Serine / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism*; D014981:Xenopus
D017630:Connexins; D008565:Membrane Proteins; D012333:RNA, Messenger; D014443:Tyrosine; D012694:Serine; D015688:Oncogene Protein pp60(v-src)