Thandi Sukhwinder, Blank Jonathan L, Challiss R A John
Department of Cell Physiology and Pharmacology, University of Leicester, University Road, Leicester, UK.
J Neurochem. 2002 Dec;83(5):1139-53. doi: 10.1046/j.1471-4159.2002.01217.x.
The coupling of the group I metabotropic glutamate receptors, mGlu1a and mGlu5a, to the extracellular signal-regulated protein kinase (ERK) pathway has been studied in Chinese hamster ovary cell-lines where receptor expression is under inducible control. Both mGlu receptors stimulated comparable, robust and agonist concentration-dependent ERK activations in the CHO cell-lines. The mGlu1a receptor-mediated ERK response was almost completely attenuated by pertussis toxin (PTx) pretreatment, whereas the mGlu5a-ERK response, and the phosphoinositide response to activation of either receptor, was PTx-insensitive. mGlu1a and mGlu5a receptor coupling to ERK occurred via mechanisms independent of phosphoinositide 3-kinase activity and intracellular and/or extracellular Ca2+ concentration. While acute treatment with a protein kinase C (PKC) inhibitor did not attenuate agonist-stimulated ERK activation, down-regulation of PKCs by phorbol ester treatment for 24 h did attenuate both mGlu1a and mGlu5a receptor-mediated responses. Further, inhibition of Src non-receptor tyrosine kinase activity by PP1 attenuated the ERK response generated by both receptor subtypes, but only mGlu1a receptor-ERK activation was attenuated by PDGF receptor tyrosine kinase inhibitor AG1296. These findings demonstrate that, although expressed in a common cell background, these closely related mGlu receptors utilize different G proteins to cause ERK activation and may recruit different tyrosine kinases to facilitate this response.
在中国仓鼠卵巢细胞系中研究了I型代谢型谷氨酸受体mGlu1a和mGlu5a与细胞外信号调节蛋白激酶（ERK）途径的偶联，该细胞系中受体表达受诱导控制。在CHO细胞系中，两种mGlu受体均刺激了相当程度的、强烈的且依赖激动剂浓度的ERK激活。mGlu1a受体介导的ERK反应几乎完全被百日咳毒素（PTx）预处理所减弱，而mGlu5a-ERK反应以及对任一受体激活的磷酸肌醇反应对PTx不敏感。mGlu1a和mGlu5a受体与ERK的偶联通过独立于磷酸肌醇3激酶活性以及细胞内和/或细胞外Ca2+浓度的机制发生。虽然用蛋白激酶C（PKC）抑制剂进行急性处理并未减弱激动剂刺激的ERK激活，但用佛波酯处理24小时使PKC下调确实减弱了mGlu1a和mGlu5a受体介导的反应。此外，PP1对Src非受体酪氨酸激酶活性的抑制减弱了两种受体亚型产生的ERK反应，但只有mGlu1a受体-ERK激活被血小板衍生生长因子受体酪氨酸激酶抑制剂AG1296减弱。这些发现表明，尽管在共同的细胞背景中表达，但这些密切相关的mGlu受体利用不同的G蛋白来引起ERK激活，并且可能募集不同的酪氨酸激酶来促进这种反应。
