Effects of cGMP-dependent phosphorylation on rat and human connexin43 gap junction channels

Brenda R. Kwak, Juan C. Sáez, Ronald Wilders, Marc Chanson, Glenn I. Fishman, Elliot L. Hertzberg, David C. Spray, Habo J. Jongsma

Research output: Contribution to journalArticle

94 Scopus citations

Abstract

The effects of 8-bromoguanosine 3′:5′-cyclic monophosphate (8Br-cGMP), a membrane-permeant activator of protein kinase G (PKG), were studied on rat and human connexin43 (Cx43), the most abundant gap junction protein in mammalian heart, which were exogenously expressed in SKHep1 cells. Under dual whole-cell voltage-clamp conditions, 8Br-cGMP decreased gap junctional conductance (gj) in rat Cx43-transfected cells by 24.0±3.7% (mean±SEM, n=5), whereas gj was not affected in human Cx43-transfected cells by the same treatment. The relaxation of gj in response to steps in transjunctional voltage observed in rat Cx43 transfectants was best fitted with three exponentials. Time constants and amplitudes of the decay phases changed in the presence of 8Br-cGMP. Single rat and human Cx43 gap junction channels were resolved in the presence of halothane. Under control conditions, three single-channel conductance states (γj) of about 20, 40-45 and 70 pS were detected, the events of the intermediate size being most frequently observed. In the presence of 8Br-cGMP, the γj distribution shifted to the lower size in rat Cx43 but not in human Cx43 transfectants. Immunoblot analyses of Cx43 in subconfluent cultures of rat Cx43 or human Cx43 transfectants showed that 8Br-cGMP did not induce changes in the electrophoretic mobility of Cx43 in either species. However, the basal incorporation of [32P] into rat Cx43 was significantly altered by 8Br-cGMP, whereas this incorporation of [32P] into human Cx43 was not affected. We conclude that 8Br-cGMP modulates phosphorylation of rat Cx43 in SKHep1 cells, but not of human Cx43. This cGMP-dependent phosphorylation of rat Cx43 is associated with a decreased gj, which results from both an increase in the relative frequency of the lowest conductance state and a change in the kinetics of these channels.

Original languageEnglish (US)
Pages (from-to)770-778
Number of pages9
JournalPflügers Archiv European Journal of Physiology
Volume430
Issue number5
DOIs
StatePublished - Sep 1 1995

Keywords

  • 8Br-cGMP
  • Channel kinetics
  • Connexin43
  • Gap junctions
  • Single channel conductance
  • Transfected cells

ASJC Scopus subject areas

  • Physiology
  • Clinical Biochemistry
  • Physiology (medical)

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    Kwak, B. R., Sáez, J. C., Wilders, R., Chanson, M., Fishman, G. I., Hertzberg, E. L., Spray, D. C., & Jongsma, H. J. (1995). Effects of cGMP-dependent phosphorylation on rat and human connexin43 gap junction channels. Pflügers Archiv European Journal of Physiology, 430(5), 770-778. https://doi.org/10.1007/BF00386175