title: Differential regulation of the tyrosine hydroxylase and enkephalin neuropeptide transmitter genes in rat PC12 cells by short chain fatty acids: concentration-dependent effects on transcription and RNA stability.
abstract: At physiologic concentrations, butyrate regulates the expression of individual genes involving at least three mechanisms: (i) through induction of cis- and trans-acting butyrate-dependent transcription factors for selected genes, (ii) by inhibition of histone deacetylation and attendant chromatin remodeling and (iii) by affecting turnover of mRNAs. Our previous work illustrated gradual accumulation of mRNA for tyrosine hydroxylase (TH), the rate-limiting enzyme in catecholamine biosynthesis and the neuropeptide transmitter proenkephalin (ppEnk) in butyrate-differentiated PC12 cells (Nankova, B.B., Chua, J., Mishra, R., Kobasiuk, C.D., La Gamma, E.F. 2003. Nicotinic induction of preproenkephalin and tyrosine hydroxylase gene expression in butyrate-differentiated rat PC12 cells: a model for adaptation to gut-derived environmental signals. Pediatr. Res. 53, 113-118.). However, at higher physiological concentrations (6 mM), TH mRNA levels are significantly reduced while ppEnk mRNA transcripts remained elevated. These differential effects suggest suppression of endogenous TH gene transcription, targeted degradation of TH mRNA or both. By using nuclear run-on assays, we found that transcription increased for both endogenous TH and ppEnk genes, even at time points and concentrations when reduced steady-state levels of TH mRNA were observed. The reduction in TH mRNA was blocked by cycloheximide consistent with a protein-dependent mechanism. We also observed a dose-dependent accumulation of luciferase reporter molecules driven by TH promoter in transient transfection experiments, data that provide additional support for separate regulatory pathways. Significantly, butyrate-dependent decreases in TH mRNA were also reflected in a reduction in TH protein. Our results suggest a novel mode of regulation for TH by butyrate operating via both transcriptional and post-transcriptional mechanisms. We speculate that, depending on plasma concentrations of butyrate, this naturally occurring signaling molecule can function as an in vivo molecular switch to alter levels of TH mRNA, its protein and thus the biosynthesis of endogenous catecholamines.
authors.affiliation: Division of Newborn Medicine, Departments of Pediatrics, Biochemistry and Molecular Biology, New York Medical College, Valhalla, NY 10595, USA.
authors.forename: Santosh
authors.initials: S
authors.lastname: Parab
authors.forename: Bistra B
authors.initials: BB
authors.lastname: Nankova
authors.forename: Edmund F
authors.initials: EF
authors.lastname: La Gamma
mesh_terms: D000818:Animals; D002087:Butyrates / Q000378:metabolism* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004745:Enkephalins / Q000096:biosynthesis / Q000235:genetics*; D005232:Fatty Acids, Volatile / Q000494:pharmacology / Q000502:physiology*; D005786:Gene Expression Regulation / Q000187:drug effects / Q000235:genetics; D009420:Nervous System / Q000187:drug effects / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D016716:PC12 Cells; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000235:genetics; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D020871:RNA Stability / Q000187:drug effects / Q000235:genetics*; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D014158:Transcription, Genetic / Q000187:drug effects / Q000235:genetics*; D015533:Transcriptional Activation / Q000187:drug effects / Q000235:genetics; D014446:Tyrosine 3-Monooxygenase / Q000096:biosynthesis / Q000235:genetics*; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics
chemical_list: D002087:Butyrates; D004745:Enkephalins; D005232:Fatty Acids, Volatile; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D014446:Tyrosine 3-Monooxygenase