Transcriptional and post-transcriptional regulation of tyrosine hydroxylase messenger RNA in PC12 cells during persistent stimulation by VIP and PACAP38: differential regulation by protein kinase A and protein kinase C-dependent pathways.
VIP and PACAP38 are closely related peptides that are released in the adrenal gland and sympathetic ganglia and regulate catecholamine synthesis and release. We used PC12 cells as a model system to examine receptor and second messenger pathways by which each peptide stimulates transcriptional and post-transcriptional mechanisms that regulate the level of the mRNA for tyrosine hydroxylase (TH), the rate-limiting enzymatic step in catecholamine synthesis. Concentration-response studies revealed that PACAP38 had both greater efficacy and potency than VIP. The specific PAC1 receptor antagonist PACAP[6-38] blocked the effects of each peptide on TH mRNA content while the PACAP/VIP type II receptor antagonist (N-AC-Tyr(1)-D-Phe(2))-GRF-(1-29)-NH(2) was without effect. At equipotent concentrations, each peptide stimulated a transient increase in TH gene transcription lasting less than 3h. Continuous VIP treatment stimulated a transient increase in TH mRNA lasting less than 24h. In contrast, continuous exposure to PACAP38 stimulated a stable increase in TH mRNA that persisted for 2 days in the absence of elevated transcription, pointing to different post-transcriptional effects of the two peptides. PACAP38 alone had no effect on the magnitude of TH gene transcription or TH mRNA in A126-1B2 PKA-deficient PC12 cells. However, when combined with dexamethasone, PACAP38 produced a synergistic increase in TH mRNA in the absence of PACAP38-stimulated TH gene transcription. In contrast, VIP had no effect on either TH mRNA content or TH gene transcription in this model. PACAP38, but not VIP, stimulated PKC activity. Calphostin C antagonized the effect of PACAP38 on the persistent post-transcriptional elevation in TH mRNA. Thus, the results support the conclusion that VIP and PACAP38 each stimulate PAC1 receptors to increase TH gene transcription through a PKA-controlled pathway, but their divergent post-transcriptional effects result at least partly from differing abilities to stimulate PKC.
Corbitt
J
J
Department of Pharmacology, University of Texas Health Science Center, San Antonio, Texas, USA.
Hagerty
T
T
Fernandez
E
E
Morgan
W W
WW
Strong
R
R
D000818:Animals; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology; D003907:Dexamethasone / Q000494:pharmacology; D004357:Drug Synergism; D004790:Enzyme Induction / Q000187:drug effects; D009281:Naphthalenes / Q000494:pharmacology; D009363:Neoplasm Proteins / Q000096:biosynthesis / Q000235:genetics; D009479:Neuropeptides / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D016716:PC12 Cells / Q000187:drug effects* / Q000201:enzymology; D010446:Peptide Fragments / Q000494:pharmacology; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D011493:Protein Kinase C / Q000502:physiology; D012323:RNA Processing, Post-Transcriptional / Q000187:drug effects*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D051236:Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide; D051237:Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide, Type I; D011979:Receptors, Pituitary Hormone / Q000037:antagonists & inhibitors / Q000187:drug effects; D018005:Receptors, Vasoactive Intestinal Peptide / Q000187:drug effects; D013997:Time Factors; D014158:Transcription, Genetic / Q000187:drug effects*; D014446:Tyrosine 3-Monooxygenase / Q000096:biosynthesis* / Q000235:genetics; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology*
C495403:Adcyap1 protein, rat; C495505:Adcyap1r1 protein, rat; D009281:Naphthalenes; D009363:Neoplasm Proteins; D009479:Neuropeptides; D010446:Peptide Fragments; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D012333:RNA, Messenger; D051236:Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide; D051237:Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide, Type I; D011979:Receptors, Pituitary Hormone; D018005:Receptors, Vasoactive Intestinal Peptide; C075647:pituitary adenylate-cyclase-activating-peptide (6-38); D014660:Vasoactive Intestinal Peptide; D003907:Dexamethasone; D014446:Tyrosine 3-Monooxygenase; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; C058819:calphostin C