Vascular abnormalities in mice deficient for the G protein-coupled receptor GPR4 that functions as a pH sensor
Vascular abnormalities in mice deficient for the G protein-coupled receptor GPR4 that functions as a pH sensor
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DOI：
10.1128/mcb.01909-06
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发表时间：
2007-02-01
影响因子：
5.3
通讯作者：
Witte, Owen N.
中科院分区：
文献类型：
--
作者：
Yang, Li V.;Radu, Caius G.;Witte, Owen N.
GPR4是一种G蛋白偶联受体，表达于血管、肺、肾等组织。体外异位过表达研究表明，GPR4可以感知细胞外pH的变化，从而导致环磷酸腺苷(CAMP)的产生。为了研究其在体内的生物学作用，我们通过同源重组产生了GPR4缺陷小鼠。虽然GPR4缺失的成年小鼠看起来表型正常，但新生儿表现出更高的围产期死亡率。在N3和N5 C57BL/6遗传背景上，GPR4(-/-)组合的平均产羔数比GPR4(+/+)组合小30%左右。部分基因敲除的胚胎和新生儿出现自发性出血、皮下血管扩张和扭曲，以及血管平滑肌细胞覆盖缺陷。GPR4缺失儿的肾小球系膜细胞也显著减少。部分新生儿出现呼吸窘迫伴呼吸道衬里细胞化生。为了研究GPR4是否参与了血管pH感知的功能，在确定的pH条件下，使用了体外主动脉环实验。与野生型主动脉相比，GPR4缺失的主动脉微血管生长受到酸性细胞外pH的抑制较小。用GPR4下游效应物cAMP的类似物治疗，可消除绕过GPR4基因敲除表型的微血管生长。这些结果表明，GPR4缺乏导致发育过程中的部分穿透性血管异常，该受体在血管pH感知中发挥作用。
GPR4 is a G protein-coupled receptor expressed in the vasculature, lung, kidney, and other tissues. In vitro ectopic overexpression studies implicated GPR4 in sensing extracellular pH changes leading to cyclic AMP (cAMP) production. To investigate its biological roles in vivo, we generated GPR4-deficient mice by homologous recombination. Whereas GPR4-null adult mice appeared phenotypically normal, neonates showed a higher frequency of perinatal mortality. The average litter size from GPR4(-/-) intercrosses was similar to 30% smaller than that from GPR4(+/+) intercrosses on N3 and N5 C57BL/6 genetic backgrounds. A fraction of knockout embryos and neonates had spontaneous hemorrhages, dilated and tortuous subcutaneous blood vessels, and defective vascular smooth muscle cell coverage. Mesangial cells in kidney glomeruli were also significantly reduced in GPR4-null neonates. Some neonates exhibited respiratory distress with airway lining cell metaplasia. To examine whether GPR4 is functionally involved in vascular pH sensing, an ex vivo aortic ring assay was used under defined pH conditions. Compared to wild-type aortas, microvessel outgrowth from GPR4-null aortas was less inhibited by acidic extracellular pH. Treatment with an analog of cAMP, a downstream effector of GPR4, abolished microvessel outgrowth bypassing the GPR4-knockout phenotype. These results suggest that GPR4 deficiency leads to partially penetrant vascular abnormalities during development and that this receptor functions in blood vessel pH sensing.