title: Cyclic AMP signalling through PKA but not Epac is essential for neurturin-induced biphasic ERK1/2 activation and neurite outgrowths through GFRα2 isoforms.
abstract: Cyclic AMP (cAMP) and neurotrophic factors are known to interact closely to promote neurite outgrowth and neuronal regeneration. Glial cell line-derived neurotrophic factor (GDNF) and its family member neurturin (NTN) transduce signal through a multi-component receptor complex consisting of GDNF family receptor alpha 2 (GFRα2) and Ret receptor tyrosine kinase. Neurons from GFRα2-deficient mice do not promote axonal initiation when stimulated by NTN, consistent with the role of GFRα2 in neuronal outgrowth. Multiple alternatively spliced isoforms of GFRα2 are known to be expressed in the nervous system. GFRα2a and GFRα2c but not GFRα2b promoted neurite outgrowth. It is currently unknown if cAMP signalling is differentially regulated by these isoforms. In this study, NTN activation of GFRα2a and GFRα2c but not GFRα2b induced biphasic ERK1/2 activation and phosphorylation of the major cAMP target CREB. Interestingly, inhibition of cAMP signalling significantly impaired GFRα2a and GFRα2c-mediated neurite outgrowth while cAMP agonists cooperated with GFRα2b to induce neurite outgrowth. Importantly, the specific cAMP effector PKA but not Epac was essential for NTN-induced neurite outgrowth, through transcription and translation-dependent activation of late phase ERK1/2. Taken together, these results not only demonstrated the essential role of cAMP-PKA signalling in NTN-induced biphasic ERK1/2 activation and neurite outgrowth, but also suggested cAMP-PKA signalling as a hitherto unrecognized underlying mechanism contributing to the differential neuritogenic activities of GFRα2 isoforms.
authors: Department of Biochemistry, National University of Singapore, Lower Kent Ridge Road, Singapore 119260, Singapore.
authors: Guoqiang
authors: G
authors: Wan
authors: Lihan
authors: L
authors: Zhou
authors: Qing 'En
authors: Q'
authors: Lim
authors: Yung Hou
authors: YH
authors: Wong
authors: Heng-Phon
authors: HP
authors: Too
mesh_terms: D000111:Acetylcysteine / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D000242:Cyclic AMP / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism / Q000494:pharmacology*; D004917:Erythromycin / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000502:physiology; D051097:Glial Cell Line-Derived Neurotrophic Factor Receptors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D020935:MAP Kinase Signaling System / Q000502:physiology; D048052:Mitogen-Activated Protein Kinase 3 / Q000235:genetics / Q000378:metabolism*; D009416:Nerve Regeneration; D016501:Neurites / Q000502:physiology*; D051101:Neurturin / Q000378:metabolism / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism*; D051096:Proto-Oncogene Proteins c-ret / Q000235:genetics / Q000378:metabolism; D051381:Rats; D060888:Real-Time Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology*; D014162:Transfection
chemical_list: C494992:Gfra2 protein, rat; D051097:Glial Cell Line-Derived Neurotrophic Factor Receptors; D051101:Neurturin; D020033:Protein Isoforms; D004917:Erythromycin; C057513:erythromycin propionate-N-acetylcysteinate; D000242:Cyclic AMP; D051096:Proto-Oncogene Proteins c-ret; D017868:Cyclic AMP-Dependent Protein Kinases; D048052:Mitogen-Activated Protein Kinase 3; D000111:Acetylcysteine