CO2 Sensitivity of Voltage Gating and Gating Polarity of GapJunction Channels—Connexin40 and its COOH-Terminus-Truncated Mutant

CO2 Sensitivity of Voltage Gating and Gating Polarity of GapJunction Channels—Connexin40 and... The CO2 sensitivity of transjunctional voltage (V j) gating was studied by dual voltage clamp in oocytes expressing mouse Cx40 or its COOH terminus (CT)-truncated mutant (Cx40-TR). V j sensitivity, determined by a standard V j protocol (20 mV V j steps, 120 mV maximal), decreased significantly with exposure to 30% CO2. The Boltzmann values of control versus CO2-treated oocytes were: V 0 = 36.3 and 48.7 mV, n = 5.4 and 3.7, and G j min = 0.21 and 0.31, respectively. CO2 also affected the kinetics of V j-dependent inactivation of junctional current (I j); the time constants of two-term exponential I j decay, measured at V j = 60 mV, increased significantly with CO2 application. Similar results were obtained with Cx40-TR, suggesting that CT does not play a role in this phenomenon. The sensitivity of Cx40 channels to 100% CO2 was also unaffected by CT truncation. There is evidence that CO2 decreases the V j sensitivity of Cx26, Cx50 and Cx37 as well, whereas it increases that of Cx45 and Cx32 channels. Since Cx40, Cx26, Cx50 and Cx37 gate at the positive side of V j, whereas Cx45 and Cx32 gate at negative V j, it is likely that V j behavior with respect to CO2-induced acidification varies depending on gating polarity, possibly involving the function of the postulated V j sensor (NH2-terminus). http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Membrane Biology Springer Journals

CO2 Sensitivity of Voltage Gating and Gating Polarity of GapJunction Channels—Connexin40 and its COOH-Terminus-Truncated Mutant

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Publisher
Springer-Verlag
Copyright
Copyright © 2004 by Springer Science+Business Media, Inc.
Subject
Life Sciences; Human Physiology; Biochemistry, general
ISSN
0022-2631
eISSN
1432-1424
D.O.I.
10.1007/s00232-004-0697-4
Publisher site
See Article on Publisher Site

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