Regulation of tyrosine hydroxylase and tetrahydrobiopterin biosynthetic enzymes in PC12 cells by NGF, EGF and IFN-gamma.
The regulation of catecholamine and tetrahydrobiopterin synthesis was investigated in cultured rat pheochromocytoma PC12 cells following treatments with nerve growth factor (NGF), epidermal growth factor (EGF) and interferon-gamma (IFN-gamma). NGF and EGF, but not IFN-gamma, caused an increase after 24 h in the levels of BH4 and catecholamines, and the activities of tyrosine hydroxylase and GTP cyclohydrolase, the rate-limiting enzymes in catecholamine and BH4 synthesis, respectively. Actinomycin D, a transcriptional inhibitor, blocked treatment-induced elevations in tyrosine hydroxylase and GTP cyclohydrolase activities. NGF, EGF or IFN-gamma did not affect the activity of sepiapterin reductase, the final enzyme in BH4 biosynthesis. Rp-cAMP, an inhibitor of cAMP-mediated responses, blocked the induction of tyrosine hydroxylase by NGF or EGF; inhibition of protein kinase C partially blocked the EGF effect, but not the NGF effect, NGF also induced GTP cyclohydrolase in a cAMP-dependent manner, while the EGF effect was not blocked by Rp-cAMP or protein kinase C inhibitors. Sphingosine induced GTP cyclohydrolase in a protein kinase C-independent manner without affecting tyrosine hydroxylase activity. Our results suggest that both tyrosine hydroxylase and GTP cyclohydrolase are induced in a coordinate and transcription-dependent manner by NGF and EGF, while conditions exist where the induction of tyrosine hydroxylase and GTP cyclohydrolase is not coordinately regulated.
Anastasiadis
P Z
PZ
William T. Gossett Neurology Laboratories, Henry Ford Health Sciences Center, Detroit, MI 48202, USA.
Kuhn
D M
DM
Blitz
J
J
Imerman
B A
BA
Louie
M C
MC
Levine
R A
RA
D000818:Animals; D001708:Biopterins / Q000031:analogs & derivatives* / Q000096:biosynthesis; D002478:Cells, Cultured; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D007371:Interferon-gamma / Q000494:pharmacology*; D009414:Nerve Growth Factors / Q000494:pharmacology*; D016716:PC12 Cells / Q000187:drug effects*; D051381:Rats; D013997:Time Factors; D014446:Tyrosine 3-Monooxygenase / Q000187:drug effects*
D009414:Nerve Growth Factors; D001708:Biopterins; D004815:Epidermal Growth Factor; D007371:Interferon-gamma; D014446:Tyrosine 3-Monooxygenase; C003402:sapropterin