| Project/Area Number |
15500266
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Neurochemistry/Neuropharmacology
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| Research Institution | Saitama Medical School |
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Principal Investigator |
SAITO Yumiko Saitama Medical School, Medicine, Assistant Professor, 医学部, 講師 (00215568)
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| Co-Investigator(Kenkyū-buntansha) |
MARUYAMA Kei Saitama Medical School, Medicine, Professor, 医学部, 教授 (30211577)
川村 勇樹 埼玉医科大学, 医学部, 助手 (50343463)
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| Project Period (FY) |
2003 – 2004
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| Project Status |
Completed (Fiscal Year 2004)
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| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2004: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 2003: ¥2,200,000 (Direct Cost: ¥2,200,000)
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| Keywords | feeding / G protein-coupled receptor / peptide / signal transduction / Gタンパク質 / カルシウム |
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| Research Abstract |
Melanin-concentrating hormone (MCH) is a hypothalamic neuropeptide that plays a key role in food intake. It acts through two G protein-coupled receptors (GPCRs), MCH1R and MCH2R, of which MCH1R is the primary regulator of food intake. We have previously reported that N-linked glycosylation of the extracellular domain of MCH1R is necessary for cell surface expression and signal transduction. We now report a role for the rat MCH1R C-terminal region. We constructed serial C-terminal truncation mutants and determined the resulting changes in protein expression, cell surface expression, ligand binding and MCH-stimulated calcium influx. By analyzing two mutants, ΔT317 (deletion of 36 C-terminal amino acids) and ΔR321 (deletion of 32 C-terminal amino acids), we found that the region between Phe^<318> and Arg^<321> was responsible for signal transduction. A more detailed analysis was performed with single or multiple residue mutations. Single mutations of Arg^<319>, Lys^<320> or Arg^<321> exhi
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bited a decrease in the cell surface expression, while mutations of either Arg^<319> or Lys^<320>, but not Arg^<321>, showed a significant reduction in the calcium influx. Simultaneous mutations of Arg^<319> and Lys^<320> produced a pronounced decrease in the efficacy of calcium influx stimulation compared with single mutations. A computational analysis revealed a dibasic amino acid motif that is conserved among many class 1 GPCRs and may be a part of the amphiphilic cytoplasmic helix 8. Our results therefore provide new insights into the role of the putative helix 8 in the regulation of GPCR function. Furthermore, we investigated the mechanism underlying the MCH-induced internalization pathway, which is important for the desensitization or regulation of the receptor response. Quantitative analysis by flow cytometry indicated that MCH1R undergoes rapid MCH-induced internalization through a PKC-, β-arrestin 2- and dynamin I-dependent pathway and that a portion of the C-terminal tail plays an important role in the internalization process. Less
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