Two zebrafish G2A homologs activate multiple intracellular signaling pathways in acidic environment.
Two zebrafish G2A homologs activate multiple intracellular signaling pathways in acidic environment.
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两种斑马鱼 G2A 同源物在酸性环境中激活多个细胞内信号通路。
DOI：
10.1016/j.bbrc.2015.11.075
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
H. Tomura
中科院分区：
文献类型：
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作者：
Y. Ichijo;Y. Mochimaru;M. Azuma;K. Satou;J. Negishi;T. Nakakura;N. Oshima;C. Mogi;K. Sato;K. Matsuda;F. Okajima;H. Tomura
人G2 A被各种刺激物激活，如溶血磷脂酰胆碱（LPC）、9-羟基十八碳二烯酸（9-HODE）和质子。该受体与多种细胞内信号传导途径偶联，包括Gs-蛋白/cAMP/CRE、G12/13-蛋白/Rho/SRE和Gq-蛋白/磷脂酶C/NFAT途径。在本研究中，我们研究了斑马鱼G2 A同源物（zG 2A-a和zG 2A-b）是否可以响应这些刺激并激活多种细胞内信号通路。我们还研究了是否组氨酸残基和碱性氨基酸残基的N-末端的同源物也发挥类似的作用，由人类G2 A残基发挥，如果同源物的正义质子。我们发现zG 2A-a在pH8.0时表现出较高的CRE、SRE和NFAT活性，而zG 2A-b在pH8.0时仅表现出较高的SRE活性。从pH 7.4至6.3的细胞外酸化改善了表达zG 2A-a的细胞中的这些活性。另一方面，酸化改善zG 2A-b表达细胞中的SRE活性，但不改善CRE和NFAT活性。LPC或9-HODE没有改变任何同源物的活性。将zG 2A-a N端174位组氨酸残基替换为天冬酰胺残基可减弱质子诱导的CRE和NFAT活性，但对SRE活性无影响。将zG 2A-a N端第32位的精氨酸残基替换为丙氨酸残基也减弱了其高的和质子诱导的CRE和NFAT活性。相反，取代没有减弱SRE活性。从zG 2A-b的N-末端至丙氨酸残基的第10位处的精氨酸残基的取代也不减弱其高或质子诱导的SRE活性。这些结果表明，斑马鱼G2 A同源物被质子激活，而不是LPC和9-HODE，同源物的激活机制类似于人类G2 A。
Human G2A is activated by various stimuli such as lysophosphatidylcholine (LPC), 9-hydroxyoctadecadienoic acid (9-HODE), and protons. The receptor is coupled to multiple intracellular signaling pathways, including the Gs-protein/cAMP/CRE, G12/13-protein/Rho/SRE, and Gq-protein/phospholipase C/NFAT pathways. In the present study, we examined whether zebrafish G2A homologs (zG2A-a and zG2A-b) could respond to these stimuli and activate multiple intracellular signaling pathways. We also examined whether histidine residue and basic amino acid residue in the N-terminus of the homologs also play roles similar to those played by human G2A residues if the homologs sense protons. We found that the zG2A-a showed the high CRE, SRE, and NFAT activities, however, zG2A-b showed only the high SRE activity under a pH of 8.0. Extracellular acidification from pH 7.4 to 6.3 ameliorated these activities in zG2A-a-expressing cells. On the other hand, acidification ameliorated the SRE activity but not the CRE and NFAT activities in zG2A-b-expressing cells. LPC or 9-HODE did not modify any activity of either homolog. The substitution of histidine residue at the 174thposition from the N-terminus of zG2A-a to asparagine residue attenuated proton-induced CRE and NFAT activities but not SRE activity. The substitution of arginine residue at the 32nd position from the N-terminus of zG2A-a to the alanine residue also attenuated its high and the proton-induced CRE and NFAT activities. On the contrary, the substitution did not attenuate SRE activity. The substitution of the arginine residue at the 10th position from the N-terminus of zG2A-b to the alanine residue also did not attenuate its high or the proton-induced SRE activity. These results indicate that zebrafish G2A homologs were activated by protons but not by LPC and 9-HODE, and the activation mechanisms of the homologs were similar to those of human G2A.