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缝隙连接通道(连接蛋白40及其COOH末端截短突变体)的电压门控的CO(2)敏感性和门控极性

CO(2) sensitivity of voltage gating and gating polarity of gapjunction channels--connexin40 and its COOH-terminus-truncated mutant.

作者信息

Peracchia C, Chen J T, Peracchia L L

机构信息

Department of Pharmacology and Physiology, University of Rochester School of Medicine, 601 Elmwood Ave., Rochester, NY 14642-8711, USA.

出版信息

J Membr Biol. 2004 Jul 15;200(2):105-13. doi: 10.1007/s00232-004-0697-4.

Abstract

The CO(2) 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% CO(2). The Boltzmann values of control versus CO(2)-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. CO(2) 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 CO(2) 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% CO(2) was also unaffected by CT truncation. There is evidence that CO(2) 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 CO(2)-induced acidification varies depending on gating polarity, possibly involving the function of the postulated V(j) sensor (NH(2)-terminus).

摘要

通过双电压钳技术研究了表达小鼠Cx40或其COOH末端(CT)截短突变体(Cx40-TR)的卵母细胞中跨连接电压(V(j))门控的CO(2)敏感性。通过标准V(j)方案(20 mV V(j)步长,最大120 mV)确定的V(j)敏感性,在暴露于30% CO(2)时显著降低。对照与CO(2)处理的卵母细胞的玻尔兹曼值分别为:V(0) = 36.3和48.7 mV,n = 5.4和3.7,以及G(j min) = 0.21和0.31。CO(2)还影响连接电流(I(j))的V(j)依赖性失活动力学;在V(j) = 60 mV下测量的双指数I(j)衰减的时间常数,随着CO(2)的施加而显著增加。用Cx40-TR获得了类似结果,表明CT在该现象中不起作用。Cx40通道对100% CO(2)的敏感性也不受CT截短的影响。有证据表明,CO(2)也会降低Cx26、Cx50和Cx37的V(j)敏感性,而增加Cx45和Cx32通道的V(j)敏感性。由于Cx40、Cx26、Cx50和Cx37在V(j)的正向门控,而Cx45和Cx32在负向V(j)门控,因此V(j)对CO(2)诱导酸化的行为可能因门控极性而异,可能涉及假定的V(j)传感器(NH(2)-末端)的功能。

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