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(Circulation Research. 2006;98:1498.)
© 2006 American Heart Association, Inc.

Cellular Biology

Selectivity of Connexin 43 Channels Is Regulated Through Protein Kinase C–Dependent Phosphorylation

Jose F. Ek-Vitorin, Timothy J. King, Nathanael S. Heyman, Paul D. Lampe, Janis M. Burt

From the Department of Physiology (J.F.E.-V., N.S.H., J.M.B.), University of Arizona, Tucson; and Division of Public Health Sciences (T.J.K., P.D.L.), Fred Hutchinson Cancer Research Center, Seattle, Wash. Present address for T.J.K.: Hawaii Biotech Inc, Aiea.

Correspondence to Janis M. Burt, PhD, University of Arizona Department of Physiology, AHSC 4103, Tucson, AZ 85724. E-mail jburt{at}u.arizona.edu

Coordinated contractile activation of the heart and resistance to ischemic injury depend, in part, on the intercellular communication mediated by Cx43-composed gap junctions. The function of these junctions is regulated at multiple levels (assembly to degradation) through phosphorylation at specific sites in the carboxyl terminus (CT) of the Cx43 protein. We show here that the selective permeability of Cx43 junctions is regulated through protein kinase C (PKC)-dependent phosphorylation at serine 368 (S368). Selective permeability was measured in several Cx43-expressing cell lines as the rate constant for intercellular dye diffusion relative to junctional conductance. The selective permeability of Cx43 junctions under control conditions was quite variable, as was the open-state behavior of the comprising channels. Coexpression of the CT of Cx43 as a distinct protein, treatment with a PKC inhibitor, or mutation of S368 to alanine, all reduced (or eliminated) phosphorylation at S368, reduced the incidence of 55- to 70-pS channels, and reduced by 10-fold the selective permeability of the junctions for a small cationic dye. Because PKC activation during preischemic conditioning is cardioprotective during subsequent ischemic episodes, we examined no-flow, ischemic hearts for Cx43 phosphorylated at S368 (pS368). Consistent with early activation of PKC, pS368-Cx43 was increased in ischemic hearts; despite extensive lateralization of total Cx43, pS368-Cx43 remained predominantly at intercalated disks. Our data suggest that the selectivity of gap junction channels at intercalated disks is increased early in ischemia.

Key Words: gap junction • connexin 43 • phosphorylation • selectivity • ischemia

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