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Tyrosine Hydroxylase Phosphorylation in Bovine Adrenal Chromaffin Cells: The Role of Intracellular Ca 2+ in the Histamine H 1 Receptor‐Stimulated Phosphorylation of Ser 8 , Ser 19 , Ser 31 , and Ser 40
Author(s) -
Bunn Stephen J.,
Sim Alistair T. R.,
Herd Lynn M.,
Austin Leone M.,
Dunkley Peter R.
Publication year - 1995
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 - 10.1046/j.1471-4159.1995.64031370.x
Subject(s) - phosphorylation , extracellular , chromaffin cell , intracellular , tyrosine hydroxylase , catecholamine , chemistry , medicine , endocrinology , biology , adrenal medulla , biochemistry , dopamine
Tyrosine hydroxylase (TOH), the rate‐limiting enzyme in catecholamine biosynthesis, is regulated by phosphorylation. Activation of histaminergic H 1 receptors on cultured bovine adrenal chromaffin cells stimulated a rapid increase in TOH phosphorylation (within 5 s) that was sustained for at least 5 min. The initial increase in TOH phosphorylation (up to 1 min) was essentially unchanged by the removal of extracellular Ca 2+ . In contrast, the H 1 ‐mediated response was abolished by preloading the cells with BAPTA acetoxymethyl ester (50 µ M ) and significantly reduced by prior exposure to caffeine (10 m M for 10 min) to deplete intracellular Ca 2+ . Trypticphosphopeptide analysis by HPLC revealed that the H 1 response in the presence or absence of extracellular Ca 2+ resulted in a major increase in the phosphorylation of Ser 19 with smaller increases in that of Ser 40 and Ser 31 . In contrast, although a brief stimulation with nicotine (30 µ M for 60 s) also resulted in a major increase in Ser 19 phosphorylation, this response was abolished in the absence of extracellular Ca 2+ . These data indicate that the mobilization of intracellular Ca 2+ plays a crucial role in supporting H 1 ‐mediated TOH phosphorylation and may thus have a potentially important role in regulating catecholamine synthesis.