C-terminal splice variants of the μ-opioid receptor:: existence, distribution and functional characteristics
C-terminal splice variants of the μ-opioid receptor:: existence, distribution and functional characteristics
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DOI：
10.1111/j.1471-4159.2007.05057.x
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发表时间：
2008-02-01
影响因子：
4.7
通讯作者：
Kelly, Eamonn
中科院分区：
文献类型：
--
作者：
Oldfield, Sue;Braksator, Ellen;Kelly, Eamonn
用RT-PCR方法检测不同剪接变异体在大鼠中枢神经系统中的分布。MOR1、MOR1A和MOR1B的mRNA种类广泛分布于大鼠中枢神经系统，MOR1mRNA和MOR1AmRNA的表达水平总体高于MOR1B。我们没有发现令人信服的证据表明MOR1C、MOR1C1、MOR1C2和MOR1D在大鼠中枢神经系统中存在显著水平。为了研究激动剂诱导的MOR1、MOR1A和MOR1B调控的可能差异，我们在HEK293细胞中表达了这些结构和G蛋白偶联的内向整流钾通道亚基，并测量了(D-丙氨酸(2)、N-Me-苯丙氨酸(4)、甘氨酚(5))-脑啡肽(DAMGO)和吗啡诱导的G蛋白偶联内向整流钾电流的脱敏速度和程度。吗啡对3种剪接变异体均有快速脱敏作用(t(1/2)：1.2~1.7min)，但DAMGO对MOR1B的脱敏作用明显减慢(t(1/2)，4.2min)。通过表达动力蛋白显性的负性突变体来抑制内吞作用增加了DAMGO诱导的MOR1B的脱敏率。这些数据表明，p-阿片受体的一些剪接变体在大鼠中枢神经系统中广泛表达，但质疑文献中已报道的其他剪接变体的存在。此外，MOR1和MOR1A的脱敏速率不依赖于激动剂，而MOR1B的脱敏速率依赖于激动剂。
The distribution of the mRNA of different C-terminal splice variants of the p-opioid receptor in rat CNS was assessed by RT-PCR. The mRNA species for MOR1, MOR1A and MOR1 B were readily detectable and distributed widely throughout the rat CNS, with levels of MOR1 and MOR1A mRNA being overall greater than for MOR1B. We did not find convincing evidence that significant levels of MOR1C, MOR1C1, MOR1C2 and MOR1D are present in rat CNS. To examine possible differences in the agonist-induced regulation of MOR1, MOR1A and MOR1B, we expressed these constructs in HEK293 cells along with G-protein-coupled inwardly rectifying K+ channel subunits and measured the rate and extent of desensitisation of (D-Ala(2),N-Me-Phe(4),glycinol(5))-enkephalin (DAMGO)- and morphine-induced G-protein-coupled inwardly rectifying K+ currents. Morphine-induced desensitisation was rapid for all three splice variants (t(1/2): 1.2-1.7 min) but DAMGO-induced desensitisation was significantly slower for MOR1 B (t(1/2), 4.2 min). Inhibition of endocytosis by expression of a dynamin-dominant negative mutant increased the rate of DAMGO-induced desensitisation of MOR1 B. These data show that some splice variants of p-opioid receptor are widely expressed in rat CNS but question the existence of others that have been reported in the literature. In addition, whereas the rate of desensitisation of MOR1 and MOR1A is agonist-independent, that for MOR1 B is agonist-dependent.