TRPC6 在中枢神经系统的作用

摘要：TRPC6(The transient receptor potential canonical 6)为瞬时受体电位(TRP)超家族的成员之一,编码钙可通透的非选择性阳离 子通道。其具有六次跨膜结构。TRPC6 同型或异型四聚体通道由TRPC6 蛋白相互结合形成或与同在一个亚家族的TRPC3, TRPC7 形成。TRPC6 通道可被G 蛋白耦联受体（GPCR）和受体酪氨酸激酶（receptor tyrosine kinases RTK）通过激活磷脂酶C (PLC)激活。其还可直接被第二信使DAG (diacylglycerol)激活。已有研究证实该通道通过激活上述信号传导通路参与了多种生理 过程。TRPC6 基因编码的蛋白在人体多个部位均有表达。TRPC6 在中枢神经系统广泛表达。其在不同部位的表达量不同,并与 TRPC家族的其他成员一起参与了多种生理过程。TRPC6 引起的细胞阳离子浓度的变化可能参与了多种神经系统疾病的发生发 展过程。因此,研究TRPC6 在中枢神经系统中的作用对疾病发病机制的了解及治疗变得更有意义。本文就TRPC6 在中枢神经系 统中的作用进行综述,并主要介绍其在树突发育,神经元保护及细胞生长方面的作用。     

TRPC6在肺部的生理与病理生理功能

经典瞬时受体电位(transient receptor potential canonical,TRPC)通道是一类非选择性钙离子通道,TRPC6是TRPC家族的成员之一,其基因编码的蛋白在人体脑、肾、肝和肺等多个器官均有表达。TRPC6不仅是肺中表达最丰富的TRPC通道,也是目前肺部疾病中研究最多的TRPC通道。TRPC6参与动物体内许多重要的生理和病理调节过程,TRPC6的基因突变或过表达可引起胞内钙离子信号通路异常,从而导致多种病理生理改变。肺部疾病的病理生理过程有多种细胞共同参与。TRPC6在不同的细胞中表达不同,表现的生理与病理生理功能则有差异。     

TRPC6与心血管疾病关系的研究进展

瞬时受体电位通道6(transient receptor potential cation channel 6,TRPC6)是瞬时受体电位离子通道家族的成员之一,属于非选择性阳离子通道。TRPC6广泛分布于大脑、神经、心脏、血管、肺、肾、胃肠道等器官组织中,可被渗透压变化、机械刺激、二酰基甘油激活,进而参与体内多种疾病的病理生理过程。研究发现,TRPC6的失调与心血管系统疾病的发病机制关系密切,且TRPC6与心血管疾病关系的研究成为近来热点。该文主要介绍TRPC6的结构特点及其与心血管系统相关疾病关系的最新研究进展。     

经典瞬时受体电位通道与细胞增殖

TRPC家族是一类能通透钙离子的非选择性阳离子通道,主要被磷脂酶C通路所激活.近年来一些研究发现.TRPC的某些成员与细胞增殖密切相关,从而参与许多疾病的病理生理过程.本文就TRPC家族成员一般特性及参与细胞增殖方面功能予以综述.     

瞬时受体电位通道在心脑血管系统疾病中的研究进展

瞬时受体电位(TRP)通道是一类重要的非选择性阳离子通道,其家族成员众多,参与多种生理病理过程。其中,TRP通道的异常表达及功能改变与心脑血管疾病的发生发展密切相关。近年研究发现,通过拮抗或者激活TRP通道可以调节血管内皮和血管平滑肌功能,参与心脑血管疾病的调控。该文主要从TRP通道的结构及各亚家族蛋白基于血管内皮和血管平滑肌对心脑血管系统疾病的作用及机制作一综述,为心脑血管疾病的防治提供新思路。     

在神经系统中TRPC1的研究进展北大核心CSCD

经典瞬时感受器电位通道1(classical transient receptor potential channel 1,TRPC1)是具有六次跨膜结构的非选择性阳离子通道,能通透钙离子和钠离子。它是哺乳类动物中第一个被发现的TRP蛋白,隶属于TRPC亚家族。TRPC1可因受体,细胞内钙库清空或机械刺激激活而开放,引起细胞内钙离子浓度的升高和细胞膜的去极化。TRPC1在神经系统内的分布较为广泛,近年来的研究显示该分子激活后引发的效应与神经系统许多生理病理过程密切相关,因此本文就目前TRPC1在神经系统中的研究进展进行综述。     

在神经系统中TRPC1的研究进展北大核心CSCD

经典瞬时感受器电位通道1(classical transient receptor potential channel 1,TRPC1)是具有六次跨膜结构的非选择性阳离子通道,能通透钙离子和钠离子。它是哺乳类动物中第一个被发现的TRP蛋白,隶属于TRPC亚家族。TRPC1可因受体,细胞内钙库清空或机械刺激激活而开放,引起细胞内钙离子浓度的升高和细胞膜的去极化。TRPC1在神经系统内的分布较为广泛,近年来的研究显示该分子激活后引发的效应与神经系统许多生理病理过程密切相关,因此本文就目前TRPC1在神经系统中的研究进展进行综述。     

在神经系统中TRPC1的研究进展北大核心CSCD

经典瞬时感受器电位通道1(classical transient receptor potential channel 1,TRPC1)是具有六次跨膜结构的非选择性阳离子通道,能通透钙离子和钠离子。它是哺乳类动物中第一个被发现的TRP蛋白,隶属于TRPC亚家族。TRPC1可因受体,细胞内钙库清空或机械刺激激活而开放,引起细胞内钙离子浓度的升高和细胞膜的去极化。TRPC1在神经系统内的分布较为广泛,近年来的研究显示该分子激活后引发的效应与神经系统许多生理病理过程密切相关,因此本文就目前TRPC1在神经系统中的研究进展进行综述。     

阻断TRPC3通道加重新生大鼠缺氧缺血性脑损伤

经典瞬时受体电位3（transient receptor potential canonical 3,TRPC3)通道是胎儿期和围生期中枢神经系统中广泛表达的非特异性阳离子通道,参与体内众多生理和病理过程。有研究证明,TRPC3通道是细胞内钙稳态的重要调节者,调节包括细胞外信号调节激酶（extracellular signal-regulated kinase,ERK）通路在内的多条钙敏感胞内信号转导通路的活性,最终影响神经元的生存或死亡。但TRPC3通道在新生动物缺氧缺血性脑损伤（hypoxic- ischemic brain damage,HIBD）模型中的作用及其机制尚未见报道。本研究取新生7 d的SD大鼠,采用右侧颈总动脉结扎和缺氧（8% O2）2~5 h制备HIBD模型,观察腹腔注射选择性TRPC3阻断剂pyr3（5 mg/kg和20 mg/kg）对缺氧缺血处理后,急性期和长期神经行为学及脑组织损伤程度的影响。神经功能缺损评分和平衡木实验结果显示,用pyr3特异性阻断TRPC3可恶化缺氧缺血大鼠的神经行为学障碍;脑组织含水量检测、TTC染色和患/健侧脑重比等结果显示,pyr3可加重脑水肿,增加脑组织梗死区体积和加重脑萎缩程度。Western印迹实验显示,缺氧缺血可以导致患侧脑组织ERK1/2磷酸化水平一过性升高,阻断TRPC3可以显著抑制ERK1/2的磷酸化,并可上调促凋亡蛋白BAX和下调抗凋亡蛋白BCL-2的表达。上述结果证明,阻断TRPC3通道可以加重新生大鼠的缺氧缺血性脑损伤,其机制可能与其对ERK信号通路活性的调节作用有关,因此可能成为HIBD治疗的潜在作用靶点。     

我国科学家发现TRPC通道新功能

突触的形成对建立神经网络十分重要。突触形成是一个复杂的过程。TRP通道是一类6次跨膜的非选择性阳离子通道。它们在进化中高度保守,在哺乳动物体内广泛表达,参与了许多重要的生理学功能,如对温度、痛觉、听觉的感知以及受精。TRPC通道是TRP的一个亚家族,在人的中枢神经系统中表达丰富,但人们对其生理功能却知之较少。     

On the potential role of source and species of diacylglycerol in phospholipase-dependent regulation of TRPC3 channels

Members of the Transient Receptor Potential Canonical (TRPC) family of channel forming proteins are among the most important Ca2+-permeable cation channels in non-excitable cells. Physiologically, TRPC channels are activated downstream receptor-dependent stimulation of phospholipases, either by store-operated or non-store operated mechanisms. TRPC3, a member of the TRPC3/6/7 subfamily, has been largely studied mostly due to its ability to function in one or the other modes, depending on cell type and expression conditions. The role of TRPC3 as a non-store operated channel has been attributed to its ability to respond to diacylglycerol (DAG) either exogenously applied or endogenously produced following activation of receptor-stimulated phospholipases. Despite the vast amount of information accumulated on this topic, some critical aspects related to phospholipase-dependent DAG-mediated regulation of TRPC3 remain unclear and/or unexplored. Among these, the source and species of native DAG, modulation by different DAG-generating phospholipases and protein kinase C-dependent inhibition of TRPC3 in its native environment are just few examples. The present essay is intended to compile existing knowledge on the nature of phospholipase-derived DAGs, their biophysical properties and current evidence on phospholipase-dependent regulation of TRPC3, to speculate on potential scenarios that may eventually provide answers to some of the above questions.     

Transient receptor potential channel 1 (TRPC1) reduces calcium permeability in heteromeric channel complexes

Specific biological roles of the classical transient receptor potential channel 1 (TRPC1) are still largely elusive. To investigate the function of TRPC1 proteins in cell physiology, we studied heterologously expressed TRPC1 channels and found that recombinant TRPC1 subunits do not form functional homomeric channels. Instead, by electrophysiological analysis TRPC1 was shown to form functional heteromeric, receptor-operated channel complexes with TRPC3, -4, -5, -6, and -7 indicating that TRPC1 proteins can co-assemble with all members of the TRPC subfamily. In all TRPC1-containing heteromers, TRPC1 subunits significantly decreased calcium permeation. The exchange of select amino acids in the putative pore-forming region of TRPC1 further reduced calcium permeability, suggesting that TRPC1 subunits contribute to the channel pore. In immortalized immature gonadotropin-releasing hormone neurons endogenously expressing TRPC1, -2, -5, and -6, down-regulation of TRPC1 resulted in increased calcium permeability and elevated basal cytosolic calcium concentrations. We did not observe any involvement of TRPC1 in store-operated cation influx. Notably, TRPC1 suppressed the migration of gonadotropin-releasing hormone neurons without affecting cell proliferation. Conversely, in TRPC1 knockdown neurons, specific migratory properties like distance covered, locomotion speed, and directionality were increased. These findings suggest a novel regulatory mechanism relying on the expression of TRPC1 and the subsequent formation of heteromeric TRPC channel complexes with reduced calcium permeability, thereby fine-tuning neuronal migration.     

N-linked protein glycosylation is a major determinant for basal TRPC3 and TRPC6 channel activity

The TRPC family of receptor-activated cation channels (TRPC channels) can be subdivided into four subfamilies based on sequence homology as well as functional similarities. Members of the TRPC3/6/7 subfamily share common biophysical characteristics and are activated by diacylglycerol in a membrane-delimited manner. At present, it is only poorly understood whether members of the TRPC3/6/7 subfamily are functionally redundant or whether they serve distinct cellular roles. By electrophysiological and fluorescence imaging strategies we show that TRPC3 displays considerable constitutive activity, while TRPC6 is a tightly regulated channel. To identify potential molecular correlates accounting for the functional difference, we analyzed the glycosylation pattern of TRPC6 compared with TRPC3. Two NX(S/T) motifs in TRPC6 were mutated (Asn to Gln) by in vitro mutagenesis to delete one or both extracellular N-linked glycosylation sites. Immunoblotting analysis of HEK 293 cell lysates expressing TRPC6 wild type and mutants favors a model of TRPC6 that is dually glycosylated within the first (e1) and second extracellular loop (e2) as opposed to the monoglycosylated TRPC3 channel (Vannier, B., Zhu, X., Brown, D., and Birnbaumer, L. (1998) J. Biol. Chem. 273, 8675-8679). Elimination of the e2 glycosylation site, missing in the monoglycosylated TRPC3, was sufficient to convert the tightly receptor-regulated TRPC6 into a constitutively active channel, displaying functional characteristics of TRPC3. Reciprocally, engineering of an additional second glycosylated site in TRPC3 to mimic the glycosylation status in TRPC6 markedly reduced TRPC3 basal activity. We conclude that the glycosylation pattern plays a pivotal role for the tight regulation of TRPC6 through phospholipase C-activating receptors.     

Protein kinase C isoenzyme: selective expression pattern of protein kinase C-θ during mouse development

Protein kinase C (PKC)-θ, a serine/threonine protein kinase and novel PKC subfamily member, has been recently identified as an essential component of the T cell synapse which activates the NF-kB signaling cascade leading to expression of the IL-2 gene during T cell activation. By RNA in situ hybridization to whole-body embryo sections it is shown that the murine PKCθ is specifically expressed in tissues with hematopoietic and lymphopoietic activity. Expression is also evident in skeletal muscle. A further highly specific expression was observed in the peripheral and central nervous system which is described in detail. Expression in the brain persists up to adult stages.     

FKBP8 is a negative regulator of mouse sonic hedgehog signaling in neural tissues

Sonic hedgehog (SHH) is a secreted morphogen that regulates the patterning and growth of many tissues in the developing mouse embryo, including the central nervous system (CNS). We show that a member of the FK506-binding protein family, FKBP8, is an essential antagonist of SHH signaling in CNS development. Loss of FKBP8 causes ectopic and ligand-independent activation of the Shh pathway, leading to expansion of ventral cell fates in the posterior neural tube and suppression of eye development. Although it is expressed broadly, FKBP8 is required to antagonize SHH signaling primarily in neural tissues, suggesting that hedgehog signal transduction is subject to cell-type specific modulation during mammalian development.     

Activation of a TRPC3-dependent cation current through the neurotrophin BDNF

Nonvoltage-gated cation currents, which are activated following stimulation of phospholipase C (PLC), appear to be major modes for Ca2+ and Na+ entry in mammalian cells. The TRPC channels may mediate some of these conductances since their expression in vitro leads to PLC-dependent cation influx. We found that the TRPC3 protein was highly enriched in neurons of the central nervous system (CNS). The temporal and spatial distribution of TRPC3 paralleled that of the neurotrophin receptor TrkB. Activation of TrkB by brain-derived nerve growth factor (BDNF) led to production of a PLC-dependent, nonselective cation conductance in pontine neurons. Evidence is provided that TRPC3 contributes to this current in vivo. Thus, activation of TrkB and PLC leads to a TRPC3-dependent cation influx in CNS neurons.     

Complex regulation of the TRPC3, 6 and 7 channel subfamily by diacylglycerol and phosphatidylinositol-4,5-bisphosphate

TRPC3, 6 and 7 channels constitute a subgroup of non-selective, calcium-permeable cation channels within the TRP superfamily that are activated by products of phospholipase C-mediated breakdown of phosphatidylinositol-4,5-bisphosphate (PIP(2)). A number of ion channels, including other members of the TRP superfamily, are regulated directly by PIP(2). However, there is little information on the regulation of the TRPC channel subfamily by PIP(2). Pretreatment of TRPC7-expressing cells with a drug that blocks the synthesis of polyphosphoinositides inhibited the ability of the synthetic diacylglycerol, oleyl-acetyl glycerol, to activate TRPC7. In excised patches, TRPC7 channels were robustly activated by application of PIP(2) or ATP, but not by inositol 1,4,5-trisphosphate. Similar results were obtained with TRPC6 and TRPC3, although the effects of PIP(2) were somewhat less and with TRPC3 there was no significant effect of ATP. In the cell-attached configuration, TRPC7 channels could be activated by the synthetic diacylglycerol analog, oleyl-acetyl glycerol. However, this lipid mediator did not activate TRPC7 channels in excised patches. In addition, channel activation by PIP(2) in excised patches was significantly greater than that observed with oleyl-acetyl glycerol in the cell-attached configuration. These findings reveal complex regulation of TRPC channels by lipid mediators. The results also reveal for the first time direct activation by PIP(2) of members of the TRPC ion channel subfamily.     

TRPC1, Orai1, and STIM1 in SOCE: Friends in tight spaces

Store-operated calcium entry (SOCE) is a ubiquitous Ca²⁺ entry pathway that is activated in response to depletion of ER-Ca²⁺ stores and critically controls the regulation of physiological functions in miscellaneous cell types. The transient receptor potential canonical 1 (TRPC1) is the first member of the TRPC channel subfamily to be identified as a molecular component of SOCE. While TRPC1 has been shown to contribute to SOCE and regulate various functions in many cells, none of the reported TRPC1-mediated currents resembled I_CRAC, the highly Ca²⁺-selective store-dependent current first identified in lymphocytes and mast cells. Almost a decade after the cloning of TRPC1 two proteins were identified as the primary components of the CRAC channel. The first, STIM1, is an ER-Ca²⁺ sensor protein involved in activating SOCE. The second, Orai1 is the pore-forming component of the CRAC channel. Co-expression of STIM1 and Orai1 generated robust I_CRAC. Importantly, STIM1 was shown to also activate TRPC1 via its C-terminal polybasic domain, which is distinct from its Orai1-activating domain, SOAR. In addition, TRPC1 function critically depends on Orai1-mediated Ca²⁺ entry which triggers recruitment of TRPC1 into the plasma membrane where it is then activated by STIM1. TRPC1 and Orai1 form discrete STIM1-gated channels that generate distinct Ca²⁺ signals and regulate specific cellular functions. Surface expression of TRPC1 can be modulated by trafficking of the channel to and from the plasma membrane, resulting in changes to the phenotype of TRPC1-mediated current and [Ca²⁺]_i signals. Thus, TRPC1 is activated downstream of Orai1 and modifies the initial [Ca²⁺]_i signal generated by Orai1 following store depletion. This review will summarize the important findings that underlie the current concepts for activation and regulation of TRPC1, as well as its impact on cell function.     

TRPC3 channels are required for synaptic transmission and motor coordination

In the mammalian central nervous system, slow synaptic excitation involves the activation of metabotropic glutamate receptors (mGluRs). It has been proposed that C1-type transient receptor potential (TRPC1) channels underlie this synaptic excitation, but our analysis of TRPC1-deficient mice does not support this hypothesis. Here, we show unambiguously that it is TRPC3 that is needed for mGluR-dependent synaptic signaling in mouse cerebellar Purkinje cells. TRPC3 is the most abundantly expressed TRPC subunit in Purkinje cells. In mutant mice lacking TRPC3, both slow synaptic potentials and mGluR-mediated inward currents are completely absent, while the synaptically mediated Ca2+ release signals from intracellular stores are unchanged. Importantly, TRPC3 knockout mice exhibit an impaired walking behavior. Taken together, our results establish TRPC3 as a new type of postsynaptic channel that mediates mGluR-dependent synaptic transmission in cerebellar Purkinje cells and is crucial for motor coordination.