Connexins regulate calcium signaling by controlling ATP release

Connexins regulate calcium signaling by controlling ATP release

^*Departments of Cell Biology and Anatomy, ^†Pathology, and ^§Neurosurgery, New York Medical College, Valhalla, NY 10595; and ^‡Department of Anatomy and Cell Biology, University of Western Ontario, London, Ontario N6A 5C1, Canada

Communicated by Louis Sokoloff, National Institute of Mental Health, Bethesda, MD (received for review July 23, 1998)

Abstract

Forced expression of gap junction proteins, connexins, enables gap junction-deficient cell lines to propagate intercellular calcium waves. Here, we show that ATP secretion from the poorly coupled cell lines, C6 glioma, HeLa, and U373 glioblastoma, is potentiated 5- to 15-fold by connexin expression. ATP release required purinergic receptor-activated intracellular Ca²⁺ mobilization and was inhibited by Cl⁻ channel blockers. Calcium wave propagation also was reduced by purinergic receptor antagonists and by Cl⁻ channel blockers but insensitive to gap junction inhibitors. These observations suggest that cell-to-cell signaling associated with connexin expression results from enhanced ATP release and not, as previously believed, from an increase in intercellular coupling.

Footnotes

↵ ¶ To whom reprint requests should be addressed. e-mail: maiken_nedergaard{at}nymc.edu.
ABBREVIATIONS:

IP3,

inositol trisphosphate;

Cx,

connexin;

Ca2+i,

intracellular calcium concentration;

CDCF,

dicarboxy-dichlorofluorescein diacetate;

2MeSATP,

2-methylthioATP;

FRAP,

fluorescence recovery after photobleach;

αGA,

18α-glycyrrhetinic acid