Permeation of Calcium through Purified Connexin 26 Hemichannels

Fiori M.C.; Figueroa, V.; Zoghbi M.E.; Sáez, J.C.; Reuss L.; Altenberg G.A.

Abstract

Gap junction channels communicate the cytoplasms of two cells and are formed by head to head association of two hemichannels, one from each of the cells. Gap junction channels and hemichannels are permeable to ions and hydrophilic molecules of up to Mr 1,000, including second messengers and metabolites. Intercellular Ca2+ signaling can occur by movement of a number of second messengers, including Ca2+, through gap junction channels, or by a paracrine pathway that involves activation of purinergic receptors in neighboring cells following ATP release through hemichannels. Understanding Ca2+ permeation through Cx26 hemichannels is important to assess the role of gap junction channels and hemichannels in health and disease. In this context, it is possible that increased Ca 2+ influx through hemichannels under ischemic conditions contributes to cell damage. Previous studies suggest Ca2+ permeation through hemichannels, based on indirect arguments. Here, we demonstrate for the first time hemichannel permeability to Ca2+ by measuring Ca2+ transport through purified Cx26 hemichannels reconstituted in liposomes. We trapped the low affinity Ca2+-sensitive fluorescent probe Fluo-5N into the liposomes and followed the increases in intraliposomal [Ca 2+] in response to an imposed [Ca2+] gradient. We show that Ca2+ does move through Cx26 hemichannels and that the permeability of the hemichannels to Ca2+ is high, similar to that for Na+. We suggest that hemichannels can be a significant pathway for Ca2+influx into cells under conditions such as ischemia. © 2012 by The American Society for Biochemistry and Molecular Biology, Inc.

Más información

Título de la Revista: JOURNAL OF BIOLOGICAL CHEMISTRY
Volumen: 287
Asunto: 48
Editorial: AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
Fecha de publicación: 2012-01-01
Página de inicio: 40826
Página final: 40834
Idioma: English
DOI/URL:

10.1074/jbc.M112.383281

Identificador: 10.1074/jbc.M112.383281
Notas: ISI, SCOPUS