血清通过调节mGluR1介导的信号通路调控细胞的生长与凋亡

血清因子能调节细胞的生长与凋亡,但是其分子机制尚不清楚.通过细胞培养基中血清存在与否,研究了代谢型谷氨酸受体1(mGluR1)介导的胞外信号调节激酶(ERK),蛋白激酶B(PKB/AKT)通路的活化及其对细胞生长与凋亡的影响.在过量表达mGluR1的HEK293细胞中,血清饥饿促进了mGluR1对ERK,AKT信号通路的活化;细胞凋亡剂STS应激损伤时,受体激动剂DHPG可降低细胞活性,促进细胞凋亡.在大鼠胶质瘤细胞中,与过表达mGluR1的HEK293细胞的结果相反,血清有助于mGluR1对ERK,AKT通路的活化作用;STS应激损伤时,内源性mGluR1的活化抑制了细胞凋亡.结果表明:血清中存在的细胞因子,通过细胞中表达水平不同的mGluR1受体,调节受体介导的信号通路,从而调控细胞生长与凋亡.本文可能揭示了一种血清调节细胞生长与凋亡的新机制.     

CAL与mGluR1相互作用抑制mGluR1过度激活诱导的细胞毒性作用

代谢型谷氨酸受体1(mGluR1)过度激活介导的谷氨酸兴奋性毒性是帕金森病(PD)的主要发病机制之一。在临床试验中应用mGluRs的负性变构调节剂缓解PD病人的运动障碍已有报道,但由于精确调控mGluRs表达或活性的局限性,目前,在PD的治疗中仍存在一些问题。因此,寻找能够精确调控mGluR1表达及活性的小分子药物或内源性基因,将有可能成为解决目前PD治疗中存在问题的有效方法。本文通过体内和体外实验,对囊性纤维跨膜调节器相关配体(CAL)在mGluR1过度激活诱导的细胞毒性中的作用和机制进行研究。研究结果显示,在工具细胞HEK293中,应用mGluR1的激动剂激活受体,CAL与mGluR1的相互作用明显增强(P< 0.05),且CAL通过与mGluR1相互作用,抑制mGluR1过度激活诱导的细胞凋亡及其下游信号通路的激活。在鱼藤酮诱导的PD大鼠模型中,过表达CAL通过抑制mGluR1下游通路的激活,减少鱼藤酮引起的神经损伤(P< 0.001)。本文揭示了一种调控mGluR1活性的新机制,希望为神经系统疾病的治疗和相关研究提供新思路。     

酸性鞘磷脂水解酶和MAPK信号通路在UVA诱导细胞凋亡中的作用

为了探讨酸性鞘磷脂水解酶 (ASM)和MAPK信号通路在UVA诱导的细胞凋亡中的作用 ,用DNA梯形条带 (DNAladder)和荧光显微镜鉴定细胞凋亡 ,Western印迹分析MAPK信号通路的激活情况 .结果显示 :①经UVA照射 ,正常的淋巴母细胞JY出现严重的细胞凋亡 ,而ASM遗传性缺陷的淋巴母细胞MS1 4 1 8出现轻微凋亡 ;给予ASM特异性抑制剂NB6 ,UVA诱导的JY细胞凋亡明显减轻 ,表明UVA诱导的细胞凋亡依赖于ASM .②UVA照射后 ,磷酸化ERK含量在MS1 4 1 8细胞中明显升高 ,在JY细胞中受到抑制 ;UVA照射前给予NB6 ,JY细胞中磷酸化ERK含量上升 ,表明ASM能抑制ERK的激活 .③UVA照射后 ,磷酸化JNK含量在MS1 4 1 8细胞中几乎没有变化 ,而在JY细胞中含量升高 ;UVA照射前给予NB6 ,JY细胞中磷酸化JNK含量没有明显升高 ,表明ASM激活JNK通路 .④NB6对UVA激活的p38MAPK信号通路没有影响 ,表明p38的激活与ASM关系不大 .研究表明 ,UVA诱导的细胞凋亡是通过激活ASM、激活JNK信号通路并抑制ERK信号通路来完成的     

肠道病毒A71型致人扁桃体上皮细胞系UT-SCC-60B凋亡和S期阻滞的研究

肠道病毒A71型(Enterovirus A71,EV-A71)是手足口病的重要病原体,为研究EV-A71感染人扁桃体上皮细胞后对细胞凋亡和细胞周期的影响,确定ERK1/2、JNK1/2、PI3K/Akt和含半胱氨酸的天冬氨酸蛋白水解酶(Cysteinyl aspartate specific proteinase,Caspase)的作用,本文以人扁桃体上皮细胞系UT-SCC-60B为细胞模型,CCK-8试剂盒检测EV-A71对UT-SCC-60B的抑制率、流式细胞仪检测EV-A71感染组和抑制剂处理组的凋亡和细胞周期、Caspase活力检测试剂盒测定Caspase-3,Caspase-8,Caspase-9活力。EV-A71以感染剂量和感染时间依赖方式抑制UT-SCC-60B增殖;EV-A71感染致UT-SCC-60B发生细胞凋亡,抑制ERK1/2、JNK1/2和PI3K/Akt能够降低UT-SCC-60B细胞凋亡比例;EV-A71感染UT-SCC-60B后发生S期阻滞,抑制ERK1/2、JNK1/2、PI3K/Akt和Caspase阻止UT-SCC-60B发生S期阻滞;EV-A71感染UT-SCC-60B能够活化Caspase-3,Caspase-8,Caspase-9且ERK1/2、JNK1/2和PI3K/Akt调控Caspase-3,Caspase-8,Caspase-9活力。因此,EV-A71能够导致人扁桃体上皮细胞UT-SCC-60B发生凋亡和S期阻滞,并且ERK1/2、JNK1/2、PI3K/Akt和Caspase参与凋亡和S期阻滞的调控。     

ERK1/2在食管鳞状细胞癌中促进细胞增殖、抑制凋亡及其调控机制的研究

探讨ERK1/2在食管鳞状细胞癌(ESCC)中对肿瘤细胞增殖、凋亡的调控及其机制。平板克隆、细胞凋亡和细胞周期实验结果发现ERK1/2 MAPK通路抑制可减弱Eca109细胞克隆形成和增殖,促进细胞凋亡,减慢细胞周期;进一步发现ERK1/2 MAPK通路抑制可以反转由mi R-21过表达诱导的Eca109细胞增殖、凋亡和周期的变化;q RT-PCR和Western-blot免疫印迹结果发现ERK1/2 MAPK信号通路抑制可以下调内源性mi R-21表达和反转外源性mi R-21诱导的ERK1/2 MAPK信号通路活化。实验结果提示ERK1/2 MAPK通路抑制可能通过下调Eca109细胞中mi R-21表达阻碍Eca109细胞增殖、促进细胞凋亡和减慢细胞周期,最终导致ESCC细胞生长抑制。     

经MAPK信号转导通路介导的糖皮质激素的作用机制

糖皮质激素(GC)通过膜受体快速激活细胞内信号传导通路的机制,主要涉及ERK,JNK/SAPK和P38等MAPK家族的重要成员.GC在许多细胞中对ERK起抑制作用,在不同的细胞中,GC能激活JNK或抑制其活性,即具有一定的细胞特异性.GC还直接或间接地激活P38途径.GC激活MAPK介导的信号传导通路,产生一系列生物学效应,如抑制细胞的生长的繁殖,介导细胞的凋亡等.     

Ras影响肿瘤的另一种机制:自噬

自噬是细胞在应激条件下或营养缺乏时,清除和降解过量或不必要的蛋白质、受损或老化的细胞器,从而维持代谢平衡的一种机制。ras是经典的癌基因,活化的Ras蛋白既可通过激活Rac1/Mkk7/JNK或Raf-1/MEK/ERK通路促进自噬,也可通过激活PI3K/Akt/m TOR1通路抑制自噬。根据细胞所处环境的不同,Ras诱导自噬对肿瘤的形成和发展产生抑制或促进作用。Ras抑制剂也可诱导自噬影响肿瘤的发展。通过干预ras基因调控肿瘤细胞自噬功能,是一种潜在的肿瘤治疗策略。     

E1A激活基因阻遏子(CREG)过表达通过抑制p38/JNK信号分子活化对抗人血管平滑肌细胞凋亡

血管平滑肌细胞(VSMCs)凋亡参与了动脉粥样硬化(AS)及冠状动脉介入治疗(PCI)术后再狭窄(RS)等心血管疾病的发生发展过程．E1A激活基因阻遏子(CREG)是新近发现的一种分泌型糖蛋白,在维持细胞和组织稳态方面发挥重要作用．前期研究发现CREG蛋白过表达能够对抗血清饥饿诱导的人血管平滑肌细胞(hVSMCs)凋亡,进一步探讨CREG对hVSMCs凋亡的调控作用及相关的分子机制．以逆转录病毒稳定转染的CREG过表达及表达抑制的hVSMCs为模型,应用两种药物Staurosporine (STS) 和Etoposide (VP-16) 诱导细胞发生凋亡,检测细胞凋亡和相关信号通路变化．结果显示,在药物干预后,CREG表达抑制时细胞凋亡明显增多,而CREG过表达明显抑制hVSMCs凋亡．同时也发现,CREG表达抑制时p38及JNK活性明显增强,而CREG过表达时p38和JNK活性被抑制．经腺病毒转染和药物干预抑制p38表达后,细胞凋亡均受到抑制,而且在p38活性被抑制的同时,JNK活化也受到抑制．说明p38和JNK表现为协同作用．结果也显示,VSMCs分化指标SM α-actin和SM MHC与CREG表达呈一致趋势,而细胞外基质蛋白Fibronection与CREG表达呈负相关．以上结果提示,CREG在维持VSMCs表型转换方面发挥重要作用,并且通过p38和JNK信号转导通路对hVSMCs凋亡进行调控．CREG可能对于AS和PCI术后RS的防治具有重要价值．     

UVB 诱导凋亡时MAPK 和Mst1/caspase-3 信号通路调节 H2B 磷酸化作用

凋亡是真核细胞执行的高度协调的程序性自杀机制. 细胞凋亡时, 组蛋白的修饰与核
内事件有关. 尤其H2B 被Mst1 激酶磷酸化后, 参与调节核内凋亡事件染色质凝聚作用. 本研究
发现, UVB诱导细胞凋亡时, H2B发生磷酸化作用, 并且受MAPK家族(ERK1/2, JNK1/2 和p38),
Mst1 和caspase-3 信号通路调控. UVB能够以时间依赖方式激活MAPK家族激酶, 进而介导H2B
磷酸化, 但是H2B 乙酰化作用不受影响. 分别阻断ERK1/2, JNK1/2 或p38 任何一种激酶, 均能
抑制H2B 磷酸化作用. 而且, UVB 也能激活caspase-3, 活化的caspase-3 激活下游Mst1. 受到激
活的Mst1 直接磷酸化H2B, 导致染色质凝聚. 但是caspase-3 和Mst1 信号通路被完全阻断时, 只
能部分抑制H2B 磷酸化作用, 同时MAPK 家族激酶的活化不受影响. 因此, 细胞在受到UVB
诱导发生凋亡时, MAPK 和caspase-3/Mst1 信号途径分别独立调节H2B 磷酸化和染色质凝聚
作用.     

PBK/TOPK在乳腺癌细胞中介导MEK非依赖性ERK激活中作用机制分析

该文探讨了乳腺癌细胞中表皮生长因子(EGF)介导的MEK非依赖性ERK激活通路。Western blot检测EGF刺激下,siRNA抑制MEK1/2后的T47D细胞的p-ERK水平,以验证T47D细胞中存在EGF介导的MEK非依赖性ERK激活的通路。接着使用可能参与MEK非依赖性ERK激活的激酶的小分子抑制剂抑制相关激酶(AC、PKC、Src、PI3K、PDK1和Akt)活性后,检测T47D细胞EGF介导ERK的磷酸化水平。siRNA抑制MEK1/2表达后,T47D细胞在EGF刺激后的仍保留部分p-ERK,即在T47D细胞中,存在EGF介导的MEK非依赖性的ERK磷酸化通路。小分子抑制剂抑制AC、PKC、Src对MEK非依赖性ERK激活途径影响不大。而使用小分子抑制剂抑制PI3K、PDK1和Akt后,ERK的磷酸化水平显著降低,提示PI3K/Akt通路下游的激酶参与T47D中EGF介导的MEK非依赖性ERK激活途径。siRNA干扰PI3K/Akt通路下游PBK/TOPK后并使用U0126抑制MEK功能后,几乎检测不到p-ERK,提示PBK/TOPK参与T47D细胞中EGF介导的MEK非依赖性ERK激活途径。乳腺癌抗雌激素药物耐药株T47D细胞存在EGF介导的MEK非依赖性ERK激活途径,且该途径受PI3K/Akt下游的PBK/TOPK调控。     

Type 2 metabotropic glutamate receptor (mGluR2) fails to negatively couple to cGMP in stably transfected cells

The group II metabotropic glutamate receptors 2 and 3 (mGluR2 and mGluR3) share sequence homology, common pharmacology and negative coupling to cAMP. We recently discovered that mGluR3 also is negatively coupled through a G-protein to the cGMP transduction pathway in rat cerebellar granule cells and astrocytes. To test the hypothesis that mGluR2 also has access to the cGMP pathway, C6 glioma cells were stably transfected with mGluR2 and mGluR3 cDNA and their coupling to cGMP levels was characterized. In contrast to many other cell lines, C6 has a robust cGMP response that makes it attractive in the study of receptor coupling to this second messenger pathway. Consistent with prior studies, the mGluR3 receptor was negatively coupled to cGMP and this coupling was blocked by PTX. In contrast, mGluR2 agonists failed to reduce sodium nitroprusside stimulated cGMP levels in transfected cell lines where the receptor was negatively coupled to cAMP. These data provide further support for the functional divergence between these two closely related receptors.     

Enhancement of glutamate uptake mediates the neuroprotection exerted by activating group II or III metabotropic glutamate receptors on astrocytes

We investigated whether the activation of astroglial group II and III metabotropic glutamate receptors (mGluRs) could exert neuroprotective effects and whether the neuroprotection was related to glutamate uptake. Our results showed that the activation of astroglial group II or III mGluRs exerted neuroprotection against 1-methyl-4-phenylpyridinium (MPP+) astroglial conditioned medium-induced neurotoxicity in midbrain neuron cultures. Furthermore, MPP+ decreased glutamate uptake of primary astrocytes and C6 glioma cells, which was recovered by activating group II or III mGluRs. Specific group II or III mGluRs antagonists completely abolished the neuroprotective effects and the enhancement of glutamate uptake of their respective agonists. Our results showed that the primary cultured rat astrocytes and C6 glioma cells expressed receptor proteins for group II mGluR2/3, group III mGluR4, mGluR6 and mGluR7. C6 glioma cells expressed mRNA for group II mGluR3, group III mGluR4, mGluR6, mGluR7 and mGluR8. In conclusion, we confirmed that the activation of astroglial mGluRs exerted neuroprotection, and demonstrated that the mechanism underlying this protective role was at least partially related to the enhancement of glutamate uptake.     

Metabotropic glutamate receptors are differentially regulated under elevated intraocular pressure

Glaucoma is a leading cause of blindness, ultimatively resulting in the apoptotic death of retinal ganglion cells. However, molecular mechanisms involved in ganglion cell death are poorly understood. While the involvement of ionotropic glutamate receptors has been extensively studied, virtually nothing is known about its metabotropic counterparts. Here, we compared the retinal gene expression of metabotropic glutamate receptors (mGluR) in eyes with normal and elevated intraocular pressure (IOP) of DBA/2J mice, a model for secondary angle-closure glaucoma using RT-PCR and immunohistochemistry. Elevated IOP in DBA/2J mice significantly increased retinal gene expression of mGluR1a, mGluR2, mGluR4a, mGluR4b, mGluR6 and mGluR7a when compared to C57BL/6 control animals, while mGluR5a/b and mGluR8a were decreased and no difference was observed for mGluR3 and mGluR8b. Specific antibodies detected an increase of mGluR1a and mGluR5a/b in both synaptic layers and in the ganglion cell layer of the retina under elevated IOP. Because ganglion cell death in DBA/2J mice occurs most likely by apoptotic mechanisms, we demonstrated up-regulation of mGluRs in neurons undergoing apoptosis. In summary, we support the idea that the specific gene regulation of mGluRs is a part of the glaucoma-like pathological process that develops in the eyes of DBA/2J mice.     

N-Acetylaspartylglutamate Selectively Activates mGluR3 Receptors in Transfected Cells

Abstract: In previous studies, we demonstrated that the neuropeptide, N -acetylaspartylglutamate (NAAG), meets the traditional criteria for a neurotransmitter and selectively activates metabotropic glutamate receptor mGluR2 or mGluR3 in cultured cerebellar granule cells and glia. Sequence homology and pharmacological data suggest that these two receptors are highly related structurally and functionally. To define more rigorously the receptor specificity of NAAG, cloned rat cDNAs for mGluR1–6 were transiently or stably transfected into Chinese hamster ovary cells and human embryonic kidney cells and assayed for their second messenger responses to the two endogenous neurotransmitters, glutamate and NAAG, as well as to metabotropic receptor agonists, trans -1-aminocyclopentane-1,3-dicarboxylate ( trans -ACPD) and l -2-amino-4-phosphonobutyrate ( l -AP4). Despite the high degree of relatedness of mGluR2 and mGluR3, NAAG selectively activated the mGluR3 receptor. NAAG activated neither mGluR2 nor mGluR1, mGluR4, mGluR5, or mGluR6. The mGluR agonist, trans -ACPD, activated each of the transfected receptors, whereas l -AP4 activated mGluR4 and mGluR6, consistent with the published selectivity of these agonists. Hybrid cDNA constructs of the extracellular domains of mGluR2 and mGluR3 were independently fused with the transmembrane and cytoplasmic domain of mGluR1a. This latter receptor domain is coupled to phosphoinositol turnover, and its activation increases intracellular calcium. The cells transfected with these chimeric receptors responded to activation by glutamate and trans -ACPD with increases in intracellular calcium. NAAG activated the chimeric receptor that contained the extracellular domain of mGluR3 and did not activate the mGluR2 chimera.     

Is the heterologous expression of metabotropic glutamate receptors (mGluRs) an appropriate method to study the mGluR function? Experience with human embryonic kidney 293 cells transfected with mGluR1

The cloning of metabotropic glutamate receptors (mgluRs) has initiated a new approach to the study of their function: the introduction of mGluR cDNA into cells that do not normally express mGluRs, thus allowing the heterologous receptor expression. We have transfected human embryonic kidney (HEK) 293 cells with the full length mGluRla cDNA and with its truncated variant which encodes the receptor termed mGluRlT (a receptor lacking the long intracellular domain and similar to the splice variant mGluR1c). Transient transfection of HEK-293 cells with mGluR1a, but not the mGluR1T cDNA, resulted in a significant increase in inositol phosphate (IP) formation in absence of any mGluR agonists. This effect was completely dependent on the presence of extracellular calcium, and unlike the agonist-stimulated IP formation it was insensitive to pertussis toxin. The prolonged activation of IP formation might affect the cell physiology. In an attempt to obtain stably transfected cells, we transfected about 1.5 × 10⁶ HEK-293 cells with the plasmide conveying the full-length mGluR1a cDNA and the neomicin-resistance gene. Only 12 clones survived the antibiotic selection, and only one of these 12 clones continued to divide. The size of mRNA from the clone was smaller than the full-length mGluR1a mRNA. The shortened mRNA, revealed in the clone, apparently encoded a functional mGluR that was sensitive to glutamate, but unlike the mGluR1a, it did not respond to 1S,3R-ACPD (1S,3R-aminocyclopentane-1,3-dicarboxylic acid). A prudent use of the heterologous cell transfection technique is necessary in studying the xfunction and the pharmacology of mGluRs.     

Effect and mechanism of mGluR6 on the biological function of rat embryonic neural stem cells

Here, we investigated the effects and molecular mechanisms of metabotropic glutamate receptor 6 (mGluR6) on rat embryonic neural stem cells (NSCs). Overexpression of mGluR6 significantly promoted the proliferation of NSCs and increased the diameter of neutrospheres after treatment for 24 h, 48 h and 72 h. Overexpression of mGluR6 promoted G1 to S phase transition, with significantly decreased cell ratio in G1/G0 phase but significantly increased cell ratio in S phase. Additionally, mGluR6 overexpression for 48 h decreased the early and late apoptosis significantly. Moreover, overexpression of mGluR6 significantly increased the expression of p-ERK1/2, Cyclin D1 and CDK2, while the expression of p-p38 was significantly decreased. On the contrary, these effects of mGluR6 overexpression were reversed by mGluR6 knockdown. In conclusion, mGluR6 promotes the proliferation of NSCs by activation of ERK1/2-Cyclin D1/CDK2 signaling pathway and inhibits the apoptosis of NSCs by blockage of the p38 MAPK signaling pathway.     

Differential Involvement of Metabotropic and p75 Neurotrophin Receptors in Effects of Nerve Growth Factor and Neurotrophin-3 on Cultured Purkinje Cell Survival

Abstract: We have examined the role of the p75 neurotrophin receptor in survival-promoting effects of nerve growth factor (NGF) and neurotrophin-3 (NT-3) on cultured Purkinje cells. Previously, we showed that NGF promotes Purkinje cell survival in conjunction with (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (ACPD), an agonist of metabotropic excitatory amino acid receptors, whereas NT-3 by itself increases cell number. We now present evidence that p75 plays different roles in Purkinje cell responses to the two neurotrophins. A metabotropic receptor of the mGluR1 subtype may interact with p75 function, so as to regulate Purkinje cell responsiveness to neurotrophins. When cerebellar cultures were grown for 6 days in the presence of ACPD and a mutant form of NGF that does not bind to p75, no increase in Purkinje cell number was observed. Moreover, the survival-promoting effect of wild-type NGF and ACPD could be inhibited by a neutralizing antiserum to p75 or by a pyrazoloquinazolinone inhibitor of neurotrophin binding to p75. In contrast, the response to NT-3 was potentiated by anti-p75 treatment and by the quinazolinone. These data indicate the mediation of p75 in the trophic response to NGF-ACPD and a negative modulatory role of p75 in the action of NT-3. To probe the role of ACPD in the p75-dependent response to NGF, metabotropic receptor subtype-specific ligands were tested. The pattern of agonist specificity implicated the mGluR1 subtype, a receptor that is expressed at high levels by Purkinje cells and linked to activation of protein kinase C (PKC). Down-regulation or blockade of PKC abolished the response to NGF-ACPD. Consistent with the opposite roles of p75 in effects of the two neurotrophins, blockade of mGluR1 or PKC potentiated the survival response elicited by NT-3. In sum, our data suggest that afferent excitatory transmitters activate specific metabotropic receptors to elicit a p75-mediated action of NGF. NT-3 acts on Purkinje cells by a different mechanism that is not absolutely p75-dependent and that is reduced by neurotrophin access to p75 and metabotropic receptor activity.     

Activation of type 4 metabotropic glutamate receptor promotes cell apoptosis and inhibits proliferation in bladder cancer

Bladder cancer, the second most common genitourinary malignancy, severely endangers the human health. Rising evidence suggests that metabotropic glutamate receptors (mGluRs) are involve in tumor progression. In this study, we observed that metabotropic glutamate receptor 4 (mGluR4) was functionally expressed in normal and cancerous bladder cells and its expression was positively correlated with high bladder cancer grading. We further confirmed that the activation of mGluR4 by VU0155041, an mGluR4-specific agonist, decreased cyclic adenosine monophosphate (cAMP) concentration and cell viability, promoted apoptosis and inhibited proliferation in bladder cancer cells, whereas MSOP (group III mGluR antagonist) or mGluR4 knockdown eliminated the effects of mGluR4 activity. Western blotting revealed the decreased cyclin D1 expression, increased procaspase-8/9/3 cleavage, and unbalanced Bcl-2/Bax expression in bladder cancer cell lines after mGluR4 activation, and likewise MSOP and mGluR4 knockdown abrogated the actions of mGluR4 activity. In vivo study showed that mGluR4 activation significantly inhibited tumor growth of bladder cancer via suppressing proliferation and promoting apoptosis. Furthermore, upregulation of phosphatase and tensin homolog (PTEN) and inhibition of Akt phosphorylation were also observed after mGluR4 activation. Similar with VU0155041, the Akt-specific inhibitor markedly promoted apoptosis and inhibited proliferation. Nevertheless, the PTEN-specific inhibitor significantly abolished the mGluR4 activation-induced cell apoptosis and proliferative inhibition in bladder cancer cell lines. These results indicate that mGluR4 can regulate the switch between survival and death via the cAMP/PTEN/AKT signaling pathway in bladder cancer cells. Our findings suggest that mGluR4 has diagnostic and prognostic potential for bladder cancer, and the development of mGluR4 agonist may be a promising strategy for bladder cancer treatment.     

Structural organization of the mouse metabotropic glutamate receptor subtype 3 gene and its regulation by growth factors in cultured cortical astrocytes.

Metabotropic glutamate receptors (mGluRs) belong to the class of G protein-coupled receptors and consist of eight different subtypes. We have characterized the structural organization of the mouse mGluR3 gene by genomic cloning in combination with rapid amplification of 5'- and 3'-cDNA ends and examined regulatory expression of mGluR3 mRNA in cultured cortical astrocytes. The mGluR3 gene consists of six exons and spans over 95 kb. Exon 1 and its preceding putative promoter are located distantly from the following protein-coding region. In the mGluR family, mGluR3 and mGluR5 are both expressed in neuronal and glial cells and are upregulated during the early postnatal period. They are, however, coupled to two distinct signaling cascades and have been shown to exert opposite influences on some functions of cultured astrocytes. In cultured astrocytes, mGluR3 and mGluR5 mRNA levels were significantly increased by exposure to epidermal growth factor (EGF), basic fibroblast growth factor (bFGF), or transforming growth factor-alpha; and EGF was more efficacious than bFGF in producing this increase. Hence, mGluR3 and mGluR5 mRNAs are concertedly upregulated in cultured astrocytes by specific growth factors. This finding suggests that the two mGluR subtypes may play an important role in maintaining the proper balance of astrocyte functions via two distinct signal transduction mechanisms.