Lynch J W, Jacques P, Pierce K D, Schofield P R
Garvan Institute of Medical Research, Sydney, New South Wales, Australia.
J Neurochem. 1998 Nov;71(5):2159-68. doi: 10.1046/j.1471-4159.1998.71052159.x.
Molecular mechanisms of zinc potentiation were investigated in recombinant human alpha1 glycine receptors (GlyRs) by whole-cell patch-clamp recording and [3H]strychnine binding assays. In the wild-type (WT) GlyR, 1 microM zinc enhanced the apparent binding affinity of the agonists glycine and taurine and reduced their concentrations required for half-maximal activation. Thus, in the WT GlyR, zinc potentiation apparently occurs by enhancing agonist binding. However, analysis of GlyRs incorporating mutations in the membrane-spanning domain M1-M2 and M2-M3 loops, which are both components of the agonist gating mechanism, indicates that most mutations uncoupled zinc potentiation from glycine-gated currents but preserved zinc potentiation of taurine-gated currents. One such mutation in the M2-M3 loop, L274A, abolished the ability of zinc to potentiate taurine binding but did not inhibit zinc potentiation of taurine-gated currents. In this same mutant where taurine acts as a partial agonist, zinc potentiated taurine-gated currents but did not potentiate taurine antagonism of glycine-gated currents, suggesting that zinc interacts selectively with the agonist transduction pathway. The intracellular M246A mutation, which is unlikely to bind zinc, also disrupted zinc potentiation of glycine currents. Thus, zinc potentiation of the GlyR is mediated via allosteric mechanisms that are independent of its effects on agonist binding.
通过全细胞膜片钳记录和[3H]士的宁结合试验，在重组人α1甘氨酸受体（GlyRs）中研究了锌增强作用的分子机制。在野生型（WT）GlyR中，1μM锌增强了激动剂甘氨酸和牛磺酸的表观结合亲和力，并降低了它们半数最大激活所需的浓度。因此，在WT GlyR中，锌增强作用显然是通过增强激动剂结合而发生的。然而，对跨膜结构域M1-M2和M2-M3环（均为激动剂门控机制的组成部分）中包含突变的GlyRs的分析表明，大多数突变使锌增强作用与甘氨酸门控电流解偶联，但保留了锌对牛磺酸门控电流的增强作用。M2-M3环中的一个这样的突变L274A消除了锌增强牛磺酸结合的能力，但不抑制锌对牛磺酸门控电流的增强作用。在这个牛磺酸作为部分激动剂的同一突变体中，锌增强了牛磺酸门控电流，但没有增强牛磺酸对甘氨酸门控电流的拮抗作用，这表明锌与激动剂转导途径选择性相互作用。细胞内M246A突变不太可能结合锌，也破坏了锌对甘氨酸电流的增强作用。因此，GlyR的锌增强作用是通过与其对激动剂结合的影响无关的变构机制介导的。
