Salah R S, Kuhn D M, Galloway M P
Department of Pharmacology, Wayne State University School of Medicine, Detroit, Michigan.
J Neurochem. 1989 May;52(5):1517-22. doi: 10.1111/j.1471-4159.1989.tb09202.x.
The hypothesis that dopamine (DA) autoreceptors modulate the phosphorylation of tyrosine hydroxylase (TH; EC 1.14.16.2) was investigated in rat striatal slices. Tissue was prelabeled with 32P inorganic phosphate, and TH recovered by immunoprecipitation with anti-TH rabbit serum. The TH monomer was resolved on sodium dodecyl sulfate polyacrylamide gels, and the extent of phosphorylation was determined by scanning densitometry of autoradiographs. Depolarization of striatal slices with 55 mM K+ markedly increased the incorporation of 32P into several proteins, including the TH monomer (Mr = 60,000). A similar increase in TH phosphorylation occurred in response to the adenylate cyclase activator forskolin and the cyclic AMP analog dibutyryl cyclic AMP. An increase in TH phosphorylation was not observed in response to the D1-selective agonist SKF 38393. The D2-selective DA autoreceptor agonist pergolide decreased the phosphorylation of TH below basal levels and blocked the increase in phosphorylation elicited by 55 mM K+. The inhibitory effect of pergolide was antagonized by the D2-selective antagonist eticlopride. Changes observed in the phosphorylation of TH were mirrored by changes in tyrosine hydroxylation in situ. These observations support the hypothesis that a reduction in TH phosphorylation is the mechanism by which DA autoreceptors modulate tyrosine hydroxylation in nigrostriatal nerve terminals.
在大鼠纹状体切片中研究了多巴胺（DA）自身受体调节酪氨酸羟化酶（TH；EC 1.14.16.2）磷酸化的假说。组织先用32P无机磷酸盐预标记，然后用抗TH兔血清通过免疫沉淀回收TH。TH单体在十二烷基硫酸钠聚丙烯酰胺凝胶上分离，磷酸化程度通过放射自显影片的扫描密度测定法确定。用55 mM K+使纹状体切片去极化显著增加了32P掺入几种蛋白质，包括TH单体（Mr = 60,000）。对腺苷酸环化酶激活剂福斯高林和环AMP类似物二丁酰环AMP的反应中，TH磷酸化也有类似增加。对D1选择性激动剂SKF 38393的反应未观察到TH磷酸化增加。D2选择性DA自身受体激动剂培高利特使TH磷酸化降至基础水平以下，并阻断了55 mM K+引起的磷酸化增加。培高利特的抑制作用被D2选择性拮抗剂依托必利拮抗。TH磷酸化的变化与原位酪氨酸羟化的变化相对应。这些观察结果支持以下假说：TH磷酸化减少是DA自身受体调节黑质纹状体神经末梢酪氨酸羟化的机制。
