IDENTIFICATION OF CCR8 AS THE SPECIFIC RECEPTOR FOR THE HUMAN BETA-CHEMOKINE I-309 - CLONING AND MOLECULAR CHARACTERIZATION OF MURINE CCR8 AS THE RECEPTOR FOR TCA-3

Chemokine receptor-like 1 (CKR-L1) was described recently as a putativ e seven-transmembrane human receptor with many of the structural featu res of chemokine receptors, To identify the ligand of CKR-L1, we have studied chemokine-induced calcium mobilization in 293 cells transfecte d with CKR-L1, Of 20 different chemokines tested, only I-309 was able to elicit a significant calcium mobilization. In addition, I-309 induc ed the transfectants to migrate in vitro. As expected for chemokine re ceptor-mediated effects, pertussis toxin, but not cholera toxin, inhib ited both the calcium flux and migration of the CKR-L1 transfectants i n response to I-309, All of these data support the conclusion that I-3 09 is a functional ligand for CKR-L1, According to the current chemoki ne receptor nomenclature, we have designated this gene as CCR8, The mu rine CCR8 (mCCR8) gene was cloned, and its predicted amino acid sequen ce showed a 71% identity with that of human CCR8. As human CCR8, mCCR8 is expressed in thymus, Both I-309 and its murine homologue TCA-3 wer e able to induce calcium mobilization in transiently transfected 293-E BNA cells expressing mCCR8. The affinity of the binding of I-125-label ed TCA-3 to mCCR8 was high (K-d approximate to 2 nM); the binding was prevented completely by an excess of cold TCA-3, and only partially co mpeted (40%) by I-309, The identification of I-309 and TCA3 as the fun ctional ligands for CCR8 receptors will help to unravel the role of th ese proteins in physiologic and pathologic situations.