title: Glial cell line-derived neurotrophic factor up-regulates GTP-cyclohydrolase I activity and tetrahydrobiopterin levels in primary dopaminergic neurones.
abstract: Glial cell line-derived neurotrophic factor (GDNF) protects dopaminergic neurones against toxic and physical damage. In addition, GDNF promotes differentiation and structural integrity of dopaminergic neurones. Here we show that GDNF can support the function of primary dopaminergic neurones by triggering activation of GTP-cyclohydrolase I (GTPCH I), a key enzyme in catecholamine biosynthesis. GDNF stimulation of primary dopaminergic neurones expressing both tyrosine 3-monooxygenase and GTPCH I resulted in a dose-dependent doubling of GTPCH I activity, and a concomitant increase in tetrahydrobiopterin levels whereas tyrosine 3-monooxygenase activity was not altered. Actinomycin D, asan inhibitor of de novo biosynthesis, abolished any GDNF-mediated up-regulation of GTPCH I activity. However, GTPCH I mRNA levels in primary dopaminergic neurones were not altered by GDNF treatment, suggesting that the mode of action for that up-regulation is not directly connected to the regulation of GTPCH I transcription. We conclude that GDNF, in addition to its action in structural differentiation, also promotes differentiation regarding expression and enzymatic activity of a crucial component in the dopaminergic biosynthetic pathway.
mesh_terms: D000818:Animals; D001708:Biopterins / Q000031:analogs & derivatives* / Q000378:metabolism*; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D003609:Dactinomycin / Q000494:pharmacology; D004298:Dopamine / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D006136:GTP Cyclohydrolase / Q000235:genetics / Q000378:metabolism*; D051100:Glial Cell Line-Derived Neurotrophic Factor; D008636:Mesencephalon / Q000166:cytology / Q000187:drug effects / Q000196:embryology / Q000378:metabolism; D009414:Nerve Growth Factors; D009419:Nerve Tissue Proteins / Q000494:pharmacology*; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects
chemical_list: C495041:Gdnf protein, rat; D051100:Glial Cell Line-Derived Neurotrophic Factor; D009414:Nerve Growth Factors; D009419:Nerve Tissue Proteins; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D003609:Dactinomycin; D001708:Biopterins; D014446:Tyrosine 3-Monooxygenase; D006136:GTP Cyclohydrolase; C003402:sapropterin; D004298:Dopamine