Colocalization of the mu-opioid receptor and calcium/calmodulin-dependent kinase II in distinct pain-processing brain regions.
Colocalization of the mu-opioid receptor and calcium/calmodulin-dependent kinase II in distinct pain-processing brain regions.
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发表时间：
2000
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通讯作者：
I. Brüggemann;S. Schulz;D. Wiborny;V. Höllt
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作者：
I. Brüggemann;S. Schulz;D. Wiborny;V. Höllt
μ阿片受体（MOR 1）介导吗啡和其他几种阿片类药物的主要镇痛作用。然而，这些药物的临床获益受到耐受性和依赖性发展的限制。在体外，μ-阿片受体在长时间的激动剂暴露期间经历快速同源脱敏。我们最近已经确定了丝氨酸残基，Ser（261）和Ser（266），在第三胞内环内的两个共识钙/钙调蛋白依赖性蛋白激酶II（CaMKII）的激动剂诱导的磷酸化和脱敏的μ-阿片受体在HEK 293细胞所需的网站。由于μ-阿片受体在体内调节的具体模式被认为取决于蛋白激酶的细胞和组织特异性补体，我们研究了MOR 1和CaMKII在大鼠大脑中使用特异性抗体之间的空间关系。我们发现，MOR 1和CaMKII α，这是一个主要的CaMKII亚型在中枢神经系统中表达共存于不同的疼痛处理的大脑区域，包括脊髓背角和背根神经节的浅层。在高倍放大下，很明显，几乎所有表达MOR 1的伤害性脊髓神经元也都含有CaMKII。在幼稚或盐水处理的动物的μ阿片受体几乎完全局限于质膜，而CaMKII定位于整个细胞质的囊泡样结构。皮下给药μ-阿片受体激动剂埃托啡后，大部分μ-阿片受体蛋白从质膜重新分布到胞质溶胶中，在胞质溶胶中它经常与CaMKII共定位。总之，我们确定CaMKII作为一种潜在的蛋白激酶，凭借其与MOR 1的共定位，可以使μ阿片受体磷酸化，从而有助于阿片类镇痛药耐受性的发展。
The mu-opioid receptor (MOR1) mediates the main analgesic effects of morphine and several other opioids. However, the clinical benefit of these drugs is limited by the development of tolerance and dependence. In vitro the mu-opioid receptor undergoes a rapid homologous desensitization during prolonged agonist exposure. We have recently identified the serine residues, Ser(261) and Ser(266), within the third intracellular loop as two consensus calcium/calmodulin-dependent protein kinase II (CaMKII) sites required for agonist-induced phosphorylation and desensitization of the mu-opioid receptor in HEK 293 cells. Since the specific pattern of mu-opioid receptor regulation in vivo is thought to depend on the cell- and tissue-specific complement of protein kinases, we examined the spatial relation between MOR1 and CaMKII in rat brain using specific antibodies. We found that MOR1 and CaMKII alpha which is a major CaMKII isoform expressed in the central nervous system co-exist in distinct pain-processing brain regions including the superficial layers of the spinal cord dorsal horn and dorsal root ganglia. At high power magnification it was evident that virtually all MOR1-expressing nociceptive spinal cord neurons also co-contain CaMKII. In naive or saline-treated animals the mu-opioid receptor was almost exclusively confined to the plasma membrane, while CaMKII was localized to vesicle-like structures throughout the cytoplasm. After subcutaneous administration of the mu-opioid receptor agonist, etorphine, a large proportion of the mu-opioid receptor proteins redistributed from the plasma membrane into the cytosol where it was frequently co-localized with CaMKII. Together, we identify CaMKII as a potential protein kinase, which by virtue of its colocalization with MOR1 may be in a position to phosphorylate the mu-opioid receptor and may thus contribute to the development of tolerance to opioid analgesics.