Carbon monoxide (CO) is a novel inhibitor of connexin hemichannels.
Hemichannels (HCs) are hexamers of connexins that can form gap-junction channels at points of cell contacts or "free HCs" at non-contacting regions. HCs are involved in paracrine and autocrine cell signaling, and under pathological conditions may induce and/or accelerate cell death. Therefore, studies of HC regulation are of great significance. Nitric oxide affects the activity of Cx43 and Cx46 HCs, whereas carbon monoxide (CO), another gaseous transmitter, modulates the activity of several ion channels, but its effect on HCs has not been explored. We studied the effect of CO donors (CORMs) on Cx46 HCs expressed in Xenopus laevis oocytes using two-electrode voltage clamp and on Cx43 and Cx46 expressed in HeLa cells using a dye-uptake technique. CORM-2 inhibited Cx46 HC currents in a concentration-dependent manner. The C-terminal domain and intracellular Cys were not necessary for the inhibition. The effect of CORM-2 was not prevented by guanylyl-cyclase, protein kinase G, or thioredoxin inhibitors, and was not due to endocytosis of HCs. However, the effect of CORM-2 was reversed by reducing agents that act extracellularly. Additionally, CO inhibited dye uptake of HeLa cells expressing Cx43 or Cx46, and MCF-7 cells, which endogenously express Cx43 and Cx46. Because CORM-2 carbonylates Cx46 in vitro and induces conformational changes, a direct effect of that CO on Cx46 is possible. The inhibition of HCs could help to understand some of the biological actions of CO in physiological and pathological conditions.
From the Centro de Fisiología Celular e Integrativa, Facultad de Medicina, Clínica Alemana Universidad del Desarrollo, Santiago, Chile 7690000 and.
Carmen G
CG
León-Paravic
From the Centro de Fisiología Celular e Integrativa, Facultad de Medicina, Clínica Alemana Universidad del Desarrollo, Santiago, Chile 7690000 and.
Vania A
VA
Figueroa
From the Centro de Fisiología Celular e Integrativa, Facultad de Medicina, Clínica Alemana Universidad del Desarrollo, Santiago, Chile 7690000 and.
Diego J
DJ
Guzmán
From the Centro de Fisiología Celular e Integrativa, Facultad de Medicina, Clínica Alemana Universidad del Desarrollo, Santiago, Chile 7690000 and.
Carlos F
CF
Valderrama
From the Centro de Fisiología Celular e Integrativa, Facultad de Medicina, Clínica Alemana Universidad del Desarrollo, Santiago, Chile 7690000 and.
Antonio A
AA
Vallejos
the Department of Cell Physiology and Molecular Biophysics, and Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, Texas 79430.
Mariana C
MC
Fiori
the Department of Cell Physiology and Molecular Biophysics, and Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, Texas 79430.
Guillermo A
GA
Altenberg
the Department of Cell Physiology and Molecular Biophysics, and Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, Texas 79430.
Luis
L
Reuss
From the Centro de Fisiología Celular e Integrativa, Facultad de Medicina, Clínica Alemana Universidad del Desarrollo, Santiago, Chile 7690000 and the Department of Cell Physiology and Molecular Biophysics, and Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, Texas 79430 mretamal@udd.cl.
Mauricio A
MA
Retamal
D000818:Animals; D002248:Carbon Monoxide / Q000494:pharmacology*; D018031:Connexin 43 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D017630:Connexins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D005978:Glutathione / Q000494:pharmacology; D006367:HeLa Cells; D006801:Humans; D061986:MCF-7 Cells; D008564:Membrane Potentials; D009942:Organometallic Compounds / Q000494:pharmacology*; D050050:Protein Carbonylation; D019163:Reducing Agents / Q000494:pharmacology; D014982:Xenopus laevis
D018031:Connexin 43; D017630:Connexins; D009942:Organometallic Compounds; D019163:Reducing Agents; C082917:GJA3 protein, human; C447082:tricarbonyldichlororuthenium (II) dimer; D002248:Carbon Monoxide; D005978:Glutathione
Carbon Monoxide; Carbonylation; Connexin; Hemichannels; Ion Channel; Post-translational Modification (PTM); Redox Signaling