Kinetic properties of the α2 homo-oligomeric glycine receptor impairs a proper synaptic functioning
Kinetic properties of the α2 homo-oligomeric glycine receptor impairs a proper synaptic functioning
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DOI：
10.1113/jphysiol.2003.052142
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发表时间：
2003-12-01
影响因子：
5.5
通讯作者：
Legendre, P
中科院分区：
文献类型：
--
作者：
Mangin, JA;Baloul, M;Legendre, P
离子型甘氨酸受体 (GlyR) 在突触接触建立之前就已存在于中枢神经系统中。已知未成熟的神经细胞（至少在脊髓中）表达α（2）同聚GlyR，与成人突触形式的GlyR（主要是α（1）/β异聚体）相比，其特性相对未知。在这里，通过外向配置的膜片钳技术结合超快流应用系统（< 100 μs），实时记录了单通道水平的 GlyR 动力学特性。在稳定转染α，GlyR亚基的中国仓鼠卵巢（CHO）细胞上进行记录。我们发现，与突触成熟 GlyR 和参与快速突触传递的其他配体门控离子通道相比，α(2) 同聚 GlyR 介导的电流的起始、松弛和脱敏要慢一到两个数量级。对单个 GlyR 通道进行的首次延迟分析表明，它们的缓慢激活时间过程是由于延迟打开造成的。当模拟甘氨酸的突触释放时（1 mM 甘氨酸；1 ms 脉冲持续时间），与成熟突触 GlyR (P-o = 0.9) 相比，α(2) 同聚 GlyR 的打开概率较低（P-o 约为 0.1）。与成熟 α(1)/β GlyR 的激活动力学相比，这种低 P-o 可能是 α(2) 同聚 GlyR 激活动力学相对较慢的直接结果。这种缓慢的动力学表明，胚胎α(2)同聚GlyR不能被成熟突触的快速神经递质释放所激活，但可能适合于非突触旁分泌样的激动剂释放，已知这种情况发生在胚胎中。
Ionotropic glycine receptors (GlyRs) are present in the central nervous system well before the establishment of synaptic contacts. Immature nerve cells are known, at least in the spinal cord, to express alpha(2) homomeric GlyRs, the properties of which are relatively unknown compared to those of the adult synaptic form of the GlyR (mainly alpha(1)/beta heteromeres). Here, the kinetics properties of GlyRs at the single-channel level have been recorded in real-time by means of the patch-clamp technique in the outside-out configuration coupled with an ultra-fast flow application system (< 100 mu s). Recordings were performed on chinese hamster ovary (CHO) cells stably transfected with the a, GlyR subunit. We show that the onset, the relaxation and the desensitisation of alpha(2) homomeric GlyR-mediated currents are slower by one or two orders of magnitude compared to synaptic mature GlyRs and to other ligand-gated ionotropic channels involved in fast synaptic transmission. First latency analysis performed on single GlyR channels revealed that their slow activation time course was due to delayed openings. When synaptic release of glycine was mimicked (1 mM glycine; 1 ms pulse duration), the opening probability of alpha(2) homomeric GlyRs was low (P-o approximate to 0.1) when compared to mature synaptic GlyRs (P-o = 0.9). This low P-o is likely to be a direct consequence of the relatively slow activation kinetics of alpha(2) homomeric GlyRs when compared to the activation kinetics of mature alpha(1)/beta GlyRs. Such slow kinetics suggest that embryonic alpha(2) homomeric GlyRs cannot be activated by fast neurotransmitter release at mature synapses but rather could be suited for a non-synaptic paracrine-like release of agonist, which is known to occur in the embryo.