Parnas Moshe, Katz Ben, Lev Shaya, Tzarfaty Vered, Dadon Daniela, Gordon-Shaag Ariela, Metzner Henry, Yaka Rami, Minke Baruch
Department of Physiology and the Kühne Minerva Center for Studies of Visual Transduction, Faculty of Medicine of The Hebrew University, Jerusalem 91120, Israel.
J Neurosci. 2009 Feb 25;29(8):2371-83. doi: 10.1523/JNEUROSCI.4280-08.2009.
Open channel block is a process in which ions bound to the inside of a channel pore block the flow of ions through that channel. Repulsion of the blocking ions by depolarization is a known mechanism of open channel block removal. For the NMDA channel, this mechanism is necessary for channel activation and is involved in neuronal plasticity. Several types of transient receptor potential (TRP) channels, including the Drosophila TRP and TRP-like (TRPL) channels, also exhibit open channel block. Therefore, removal of open channel block is necessary for the production of the physiological response to light. Because there is no membrane depolarization before the light response develops, it is not clear how the open channel block is removed, an essential step for the production of a robust light response under physiological conditions. Here we present a novel mechanism to alleviate open channel block in the absence of depolarization by membrane lipid modulations. The results of this study show open channel block removal by membrane lipid modulations in both TRPL and NMDA channels of the photoreceptor cells and CA1 hippocampal neurons, respectively. Removal of open channel block is characterized by an increase in the passage-rate of the blocking cations through the channel pore. We propose that the profound effect of membrane lipid modulations on open channel block alleviation, allows the productions of a robust current in response to light in the absence of depolarization.
开放通道阻滞是一种离子与通道孔内部结合从而阻断离子通过该通道流动的过程。去极化对阻滞离子的排斥是已知的开放通道阻滞解除机制。对于NMDA通道,这种机制是通道激活所必需的,并且参与神经元可塑性。包括果蝇TRP通道和TRP样(TRPL)通道在内的几种瞬时受体电位(TRP)通道也表现出开放通道阻滞。因此,解除开放通道阻滞对于产生对光的生理反应是必要的。由于在光反应发生之前没有膜去极化,目前尚不清楚开放通道阻滞是如何解除的,而这是在生理条件下产生强烈光反应的关键步骤。在此,我们提出一种新机制,即在没有去极化的情况下通过膜脂质调节来减轻开放通道阻滞。本研究结果表明,膜脂质调节分别在光感受器细胞和海马CA1神经元的TRPL通道和NMDA通道中解除了开放通道阻滞。开放通道阻滞的解除表现为阻滞阳离子通过通道孔的通过率增加。我们认为,膜脂质调节对减轻开放通道阻滞具有深远影响,使得在没有去极化的情况下对光产生强烈电流成为可能。