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Titolo:
Rapid and direct effects of pH on connexins revealed by the connexin46 hemichannel preparation
Autore:
Trexler, EB; Bukauskas, FF; Bennett, MVL; Bargiello, TA; Verselis, VK;
Indirizzi:
Yeshiva Univ Albert Einstein Coll Med, Dept Neurosci, Bronx, NY 10461 USA Yeshiva Univ Albert Einstein Coll Med Bronx NY USA 10461 nx, NY 10461 USA
Titolo Testata:
JOURNAL OF GENERAL PHYSIOLOGY
fascicolo: 5, volume: 113, anno: 1999,
pagine: 721 - 742
SICI:
0022-1295(199905)113:5<721:RADEOP>2.0.ZU;2-Y
Fonte:
ISI
Lingua:
ENG
Soggetto:
GAP JUNCTION CHANNELS; MARIE-TOOTH-DISEASE; XENOPUS-OOCYTES; CONDUCTANCE STATES; VOLTAGE DEPENDENCE; MOLECULAR ANALYSIS; INTRACELLULAR PH; CURRENTS; PROTEIN; SENSITIVITY;
Keywords:
connexin; intercellular communication; ion channel; pH; gating;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
45
Recensione:
Indirizzi per estratti:
Indirizzo: Verselis, VK Yeshivaronx, Albert Einstein Coll Med, Dept Neurosci, 1300 Morris Pk Ave, B Yeshiva Univ Albert Einstein Coll Med 1300 Morris Pk Ave Bronx NY USA 10461
Citazione:
E.B. Trexler et al., "Rapid and direct effects of pH on connexins revealed by the connexin46 hemichannel preparation", J GEN PHYSL, 113(5), 1999, pp. 721-742

Abstract

PH is a potent modulator of gap junction (GJ) mediated cell-cell communication. Mechanisms proposed for closure of GJ channels by acidification include direct actions of H+ on GJ proteins and indirect actions mediated by soluble inter mediates. Here we report on the effects of acidification on connexin (Cx;)46 cell-cell channels expressed in Neuro-2a cells and Cx46 hemichannels expressed in Xenopus oocytes. Effects of acidification on hemichannels were examined macroscopically and in excised patches that permitted rapid (<1 ms) and uniform pH changes at the er;posed hemichannel face. Both types of Cx46 channel were found to be sensitive to cytoplasmic pH, and two effects were evident. A rapid and reversible closure,vas reproducibly elicited with short exposures to low pH, and a poorly reversible or irreversible loss occurred with longer exposures. We attribute the former to pH gating and the latter to pH inactivation. Half-maximal reduction of open probabilityfor pH gating in hemichannels occurs at PII 6.4. Hemichannels remained sensitive to cytoplasmic pH when excised and when cytoplasmic [Ca2+] was maintained near resting (similar to 10(-7);M) levels. Thus, Cx46 hemichannel pH gating does not depend on cytoplasmic intermediates ol a rise in [Ca2+]. Rapid application of low pH to the cytoplasmic face of open hemichannels resulted in a minimum latency to closure near zero, indicating that Cx46 hemichannels directly sense pH. Application to closed hemichannels extended theirclosed time, suggesting that the pH sensor is accessible fr om the cytoplasmic side of a closed hemichannel. Rapid closure with significantly reducedsensitivity was observed with low pH application to the extracellular face, but could be explained by H+ permeation through the pore to reach an internal site. Closure by pH is voltage dependent and has the same polarity with low pH applied to either side. These data suggest that the pH sensor is located directly on Cx46 near the pc:,re entrance on the cytoplasmic side.

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Documento generato il 15/07/20 alle ore 15:01:30