Nitric oxide specifically reduces the permeability of Cx37-containing gap junctions to small molecules.
Gap junction intercellular communication (GJIC) plays a significant role in the vascular system. Regulation of GJIC is a dynamic process, with alterations in connexin (Cx) protein expression and post-translational modification as contributing mechanisms. We hypothesized that the endothelial autacoid nitric oxide (NO) would reduce dye coupling in human umbilical vein endothelial cells (HUVECs). In our subsequent experiments, we sought to isolate the specific Cx isoform(s) targeted by NO or NO-activated signaling pathways. Since HUVEC cells variably express three Cx (Cx37, Cx40, and Cx43), this latter aim required the use of transfected HeLa cells (HeLaCx37, HeLaCx43), which do not express Cx proteins in their wild type form. Dye coupling was measured by injecting fluorescent dye (e.g., Alexa Fluor 488) into a single cell and determining the number of stained adjacent cells. Application of the NO donor SNAP (2 microM, 20 min) reduced dye coupling in HUVEC by 30%. In HeLa cells, SNAP did not reduce dye transfer of cells expressing Cx43, but decreased the dye transfer from Cx37-expressing cells to Cx43-expressing cells by 76%. The effect of SNAP on dye coupling was not mediated via cGMP. In contrast to its effect on dye coupling, SNAP had no effect on electrical coupling, measured by a double patch clamp in whole cell mode. Our results demonstrate that NO inhibits the intercellular transfer of small molecules by a specific influence on Cx37, suggesting a potential role of NO in controlling certain aspects of vascular GJIC.
Institute of Physiology, Ludwig-Maximilians-University Munich, Schillerstr, Munich, Germany. Petra.Kameritsch@lrz.uni-muenchen.de
Petra
P
Kameritsch
Natascha
N
Khandoga
Wolfram
W
Nagel
Christina
C
Hundhausen
Darcy
D
Lidington
Ulrich
U
Pohl
D002199:Capillary Permeability / Q000187:drug effects / Q000502:physiology*; D018031:Connexin 43 / Q000235:genetics / Q000378:metabolism; D017630:Connexins / Q000235:genetics / Q000378:metabolism*; D006152:Cyclic GMP / Q000378:metabolism; D004553:Electric Conductivity; D004730:Endothelium, Vascular / Q000166:cytology / Q000502:physiology; D005456:Fluorescent Dyes / Q000493:pharmacokinetics; D017629:Gap Junctions / Q000187:drug effects / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008970:Molecular Weight; D009569:Nitric Oxide / Q000502:physiology*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D026423:S-Nitroso-N-Acetylpenicillamine / Q000494:pharmacology; D014162:Transfection; D014471:Umbilical Veins / Q000166:cytology; D000097006:Gap Junction alpha-4 Protein
D018031:Connexin 43; D017630:Connexins; D006152:Cyclic GMP; D005456:Fluorescent Dyes; D009569:Nitric Oxide; D020030:Nitric Oxide Donors; D026423:S-Nitroso-N-Acetylpenicillamine; D000097006:Gap Junction alpha-4 Protein