Human connexin40 gap junction channels are modulated by cAMP

Objective: Gap junction channels provide for direct electrical coupling bet ween cells, and play an important role in homeostasis and electrical coupli ng. One of the proteins that form gap junctions, Connexin40 (Cx40), shows r estricted expression in the body, and is found in blood vessels and in the atrium and conduction system of the heart. We have investigated whether gap junction channels formed of Cx40 are modulated by protein-kinase-A-mediate d phosphorylation. Methods: A communication-deficient human hepatoma cell l ine (SKHep1) was stably transfected with human Cx40 cDNA and the properties of Cx40 gap junctions channels and their modulation by cAMP were analyzed using immunocytochemistry, Western blotting, dual patch clamp, and dye coup ling. Results: Administration of 1 mM 8-Br-cAMP resulted in a mobility shif t of Cx40 protein on western blot and increased macroscopic gap junctional conductance between cell pairs by 46.2 +/- 12.0% (mean +/- S.E.M., n=8). Un der control conditions, single channel experiments revealed three single ch annel conductances around 30, 80 and 120 pS. When cAMP was added, channel c onductances of 46 and 120 pS were observed. In monolayers, cAMP also increa sed the permeability of Cx40 gap junction channels for Lucifer Yellow by 58 %. Conclusions: Macroscopic conductance and permeability of Cx40 gap juncti ons is strongly increased by cAMP and may play a role in the regulation of intercellular communication in the heart and vasculature. (C) 2000 Elsevier Science BN. All rights reserved.