Aromatic D-amino acids act as chemoattractant factors for human leukocytes through a G protein-coupled receptor, GPR109B
Aromatic D-amino acids act as chemoattractant factors for human leukocytes through a G protein-coupled receptor, GPR109B
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DOI：
10.1073/pnas.0811844106
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发表时间：
2009-03-10
影响因子：
11.1
通讯作者：
Sakurai, Takeshi
中科院分区：
文献类型：
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作者：
Irukayama-Tomobe, Yoko;Tanaka, Hirokazu;Sakurai, Takeshi
GPR109B （HM74）是一种假定的G蛋白偶联受体（GPCR），其同源配体尚未被表征。GPR109B与另一种被鉴定为高亲和力烟酸受体的GPR109A序列高度相似。而烟酸对GPR109B的亲和力很低。在本研究中，我们发现某些芳香d -氨基酸，包括d -苯丙氨酸、d -色氨酸及其代谢物d -犬尿氨酸，通过激活百日毒（PTX）敏感的G蛋白，降低了转染GPR109B cDNA的细胞中腺苷酸环化酶的活性。这些d -氨基酸还以ptx敏感的方式在表达GPR109B的细胞中引起细胞内Ca2+水平的短暂升高。相反，这些d -氨基酸对表达GPR109A的细胞没有任何影响。我们发现GPR109B mRNA在人中性粒细胞中大量表达。d -苯丙氨酸和d -色氨酸诱导人中性粒细胞细胞内Ca2+水平的短暂增加和cAMP水平的降低。此外，通过RNA干扰敲低GPR109B可以抑制d -氨基酸诱导的人中性粒细胞细胞cAMP水平的下降。这些d -氨基酸诱导了新鲜制备的人中性粒细胞的趋化活性。我们还发现，d -苯丙氨酸和d -色氨酸在转染GPR109B cDNA的Jurkat细胞中诱导趋化反应，而在模拟转染的Jurkat细胞中则没有。这些结果表明，这些芳香d -氨基酸通过激活GPR109B在人中性粒细胞中引起趋化反应。
GPR109B (HM74) is a putative G protein-coupled receptor (GPCR) whose cognate ligands have yet to be characterized. GPR109B shows a high degree of sequence similarity to GPR109A, another GPCR that was identified as a high-affinity nicotinic acid (niacin) receptor. However, the affinity of nicotinic acid to GPR109B is very low. In this study, we found that certain aromatic D-amino acids, including D-phenylalanine, D-tryptophan, and the metabolite of the latter, D-kynurenine, decreased the activity of adenylate cyclase in cells transfected with GPR109B cDNA through activation of pertussis toxin (PTX)-sensitive G proteins. These D-amino acids also elicited a transient rise of intracellular Ca2+ level in cells expressing GPR109B in a PTX-sensitive manner. In contrast, these D-amino acids did not show any effects on cells expressing GPR109A. We found that the GPR109B mRNA is abundantly expressed in human neutrophils. D-phenylalanine and D-tryptophan induced a transient increase of intracellular Ca2+ level and a reduction of cAMP levels in human neutrophils. Furthermore, knockdown of GPR109B by RNA interference inhibited the D-amino acids-induced decrease of cellular cAMP levels in human neutrophils. These D-amino acids induced chemotactic activity of freshly prepared human neutrophils. We also found that D-phenylalanine and D-tryptophan induced chemotactic responses in Jurkat cells transfected with the GPR109B cDNA but not in mock-transfected Jurkat cells. These results suggest that these aromatic D-amino acids elicit a chemotactic response in human neutrophils via activation of GPR109B.