中文摘要：

C5a Like Receptor2——5L2，又称G蛋白偶联受体77（GPR77），是C5aR（CD88）亚家族成员，在氨基酸序列上与C5aR（CD88）有35％的同源性。广泛分布于全身各组织细胞，在粒细胞和未成熟树突状细胞（immature dendritic ）及脾脏中有大量的表达。由于长期以来未发现其生理性配体而被称为孤儿受体（orphan receptor）。当前大量研究表明C5L2能与C5a，C3a，C4a，去精CSa（C5a des-An^74）和去精C3a（C3a des-Arg^77）结合，且与CSades-Arg^74结合能力比CD88与CSades-Arg^74高10倍。在结构、功能等方面与CD88也有很多相似之处。与CD88不同的是由于C5L2第三跨膜片断末端的DRY序列上精氨酸被亮氨酸替代，有一个更短的胞内第三环，缺乏丝氨酸，苏氨酸残基，所以不能强有力地与G蛋白偶联，和C5a结合后仅诱导转染细胞发生微弱的磷酸化，不引起细胞内钙的流动及转染细胞脱颗粒；C5L2与配体结合后不发生内化，并具有与配体缓慢的结合与解离的特性。作为过敏毒素受体，CSL2在过敏毒素C5a参与的相关疾病，如脓毒症（sepsis）、急性肺损伤（ALI）、急性呼吸窘迫综合征（ARDs）等的发生、发展以及对G蛋白偶联受体的研究都具有重要的意义。

英文摘要：

The anaphylatoxin C5a exerts a plethora of biologic activities critical in the pathogenesis of systemic inflammatory disease. Initially, a novel orphan receptor, C5L2, was detected on PMN and immature dendritic cells without evidence of intracellular signaling. The current studies report that C5L2, belonging to a subfamily of CSa receptor, has a high affinity for C5a and C5a des Arg^34, and shares 35% amino acid identity with CSaR（CD88）. C5L2 also has a moderate affinity for anaphylatoxin C3a, C3a des-Arg^77 and CAa. Because of an amino acid alteration in the so-called DRY sequence at the end of the third transmembrane segement, C5L2 does not support degranulation or increases in intracellular Ca^2 ＋ and is not rapidly internalized or stimulated chemotaxis in resporee to ligand binding. C5L2 has a slow ligand on and off rates. These biophysical properties of the C5L2 suggest that this receptor is an anaphylatoxin-binding protein with unique liond binding and signaling properies. C5L2 plays a role in the disease involved in anapltoxin C5a and has significance for the study of G protein coupled receptor. C5L2 is also a valuable tool for studying the biological activities of C5a and C5a des Arg^74.