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Activation and Multiple‐Site Phosphorylation of Tyrosine Hydroxylase in Perfused Rat Adrenal Glands
Author(s) -
Haycock John W.,
Wakade Arun R.
Publication year - 1992
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1992.tb09276.x
Subject(s) - vasoactive intestinal peptide , phosphorylation , endocrinology , muscarine , medicine , adrenal medulla , tyrosine hydroxylase , stimulation , second messenger system , chemistry , tyrosine , protein phosphorylation , secretagogue , tyrosine phosphorylation , biology , catecholamine , protein kinase a , intracellular , biochemistry , dopamine , neuropeptide , receptor , muscarinic acetylcholine receptor
Tryptic digestion of tyrosine hydroxylase (TH) isolated from rat adrenal glands labeled with 32 P i produced five phosphopeptides. Based on the correspondence of these phosphopeptides with those identified in TH from rat pheochromocytoma cells, four phosphorylation sites (Ser 8 , Ser 19 , Ser 31 , and Ser 40 ) were inferred. Field stimulation of the splanchnic nerves at either 1 or 10 Hz (300 pulses) increased 32 P incorporation into TH. At 10 Hz, the phosphorylation of Ser 19 and Ser 40 was increased, whereas at 1 Hz, Ser 19 , Ser 31 , and Ser 40 phosphorylation was increased. Stimulation at either 1 or 10 Hz also increased the catalytic activity of TH, as measured in vitro (pH 7.2) at either 30 or 300 μ M tetrahydrobiopterin. Nicotine (3 μ M , 3 min) increased Ser 19 phosphorylation, vasoactive intestinal polypeptide (10 μ M , 3 min) increased Ser 40 phosphorylation, and muscarine (100 μ M , 3 min) increased TH phosphorylation primarily at Ser 19 and Ser 31 . Vasoactive intestinal polypeptide, but not nicotine or muscarine, mimicked the effects of field stimulation on TH activity. Thus, the regulation of rat adrenal medullary TH phosphorylation by nerve impulses is mediated by multiple first and second messenger systems, as previously shown for catecholamine secretion. However, different sets of second messengers are involved in the two processes. The action of vasoactive intestinal polypeptide as a secretagogue involves the mobilization of intracellular calcium, whereas its effects on TH phosphorylation are mediated by cyclic AMP. This latter effect of vasoactive intestinal polypeptide and the consequent increase in Ser 40 phosphorylation appear to be responsible for the rapid activation of TH by splanchnic nerve stimulation.