title: Ghrelin suppresses Purkinje neuron P-type Ca(2+) channels via growth hormone secretagogue type 1a receptor, the βγ subunits of Go-protein, and protein kinase a pathway.
abstract: Although ghrelin receptors have been demonstrated to be widely expressed in the central nervous system and peripheral tissues of mammals, it is still unknown whether ghrelin functions in cerebellar Purkinje neurons. In this study, we identified a novel functional role for ghrelin in modulating P-type Ca(2+) channel (P-type channel) currents (IBa) as well as action-potential firing in rat Purkinje neurons. Our results show that ghrelin at 0.1μM reversibly decreased IBa by ~32.3%. This effect was growth hormone secretagogue receptor 1a (GHS-R1a)-dependent and was associated with a hyperpolarizing shift in the voltage-dependence of inactivation. Intracellular application of GDP-β-S and pretreatment with pertussis toxin abolished the inhibitory effects of ghrelin. Dialysis of cells with the peptide QEHA (but not the scrambled peptide SKEE), and a selective antibody raised against the G-protein αo subunit both blocked the ghrelin-induced response. Ghrelin markedly increased protein kinase A (PKA) activity, and intracellular application of PKI 5-24 as well as pretreatment of the cells with the PKA inhibitor KT-5720 abolished ghrelin-induced IBa decrease, while inhibition of PKC had no such effects. At the cellular level, ghrelin induced a significant increase in action-potential firing, and blockade of GHS-R1a by BIM-28163 abolished the ghrelin-induced hyperexcitability. In summary, these results suggest that ghrelin markedly decreases IBa via the activation of GHS-R1a, which is coupled sequentially to the activities of Go-protein βγ subunits and the downstream PKA pathway. This could contribute to its physiological functions, including the spontaneous firing of action potentials in cerebellar Purkinje neurons.
authors.affiliation: Department of Neurology, Shanghai Jiaotong University Affiliated Sixth People's Hospital, Shanghai 200233, PR China.
authors.forename: Yameng
authors.initials: Y
authors.lastname: Sun
authors.affiliation: Department of Neurology, Shanghai Pudong New District Zhoupu Hospital, Shanghai 201138, PR China.
authors.forename: Nan
authors.initials: N
authors.lastname: Shi
authors.affiliation: National Shanghai Center for New Drug Safety Evaluation and Research, Shanghai 201203, PR China.
authors.forename: Hua
authors.initials: H
authors.lastname: Li
authors.affiliation: Department of Neurology, Shanghai Pudong New District Zhoupu Hospital, Shanghai 201138, PR China. Electronic address: liukangyong555@163.com.
authors.forename: Kangyong
authors.initials: K
authors.lastname: Liu
authors.affiliation: Department of Neurology, Shanghai Pudong New District Zhoupu Hospital, Shanghai 201138, PR China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Neurology, Shanghai Jiaotong University Affiliated Sixth People's Hospital, Shanghai 200233, PR China.
authors.forename: Wenqi
authors.initials: W
authors.lastname: Chen
authors.affiliation: Department of Neurology, Shanghai Jiaotong University Affiliated Sixth People's Hospital, Shanghai 200233, PR China. Electronic address: sunxiaojiangsh@163.com.
authors.forename: Xiaojiang
authors.initials: X
authors.lastname: Sun
mesh_terms: D000818:Animals; D020865:Calcium Channels, P-Type / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D017868:Cyclic AMP-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation / Q000502:physiology; D044387:GTP-Binding Protein beta Subunits / Q000235:genetics / Q000378:metabolism*; D044388:GTP-Binding Protein gamma Subunits / Q000235:genetics / Q000378:metabolism*; D054439:Ghrelin / Q000235:genetics / Q000378:metabolism*; D011689:Purkinje Cells / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D054440:Receptors, Ghrelin / Q000235:genetics / Q000378:metabolism*
chemical_list: D020865:Calcium Channels, P-Type; D044387:GTP-Binding Protein beta Subunits; D044388:GTP-Binding Protein gamma Subunits; D054439:Ghrelin; D054440:Receptors, Ghrelin; D017868:Cyclic AMP-Dependent Protein Kinases
keywords: Ghrelin; P-type Ca(2+) channels; Protein kinase A; Purkinje neuron