Gong X, Gong W, Kuhns D B, Ben-Baruch A, Howard O M, Wang J M
Intramural Research Support Program,SAIC-Frederick, NCI-FCRDC, Frederick, Maryland 21702, USA.
J Biol Chem. 1997 May 2;272(18):11682-5. doi: 10.1074/jbc.272.18.11682.
Monocyte chemotactic protein (MCP)-2 is a member of the C-C chemokine subfamily, which shares more than 60% sequence homology with MCP-1 and MCP-3 and about 30% homology with macrophage inflammatory protein (MIP)-1alpha, regulated on activation of normal T cell expressed (RANTES), and MIP-1beta. Despite this considerable sequence homology to other C-C chemokines, MCP-2 appears to have unique functional properties in comparison with other C-C chemokines such as MCP-1 and MCP-3. Although evidence obtained from studies on leukocytes suggested that MCP-2 may share the receptors with these C-C chemokines, the actual functional receptors for MCP-2 have not yet been identified. In this study, by using radioiodinated MCP-2, we identified high affinity binding sites for MCP-2 on human peripheral blood monocytes. The MCP-2 binding was competed for by MCP-1 and MCP-3, but less well by MIP-1alpha or RANTES. In experiments using cells transfected with C-C chemokine receptors, 125I-MCP-2 bound to human embryonic kidney 293 cells transfected with CCR1 or CCR2B, known to also bind MIP-1alpha/RANTES and MCP-1, respectively, but both shared by MCP-3. The binding of 125I-MCP-2 to these receptor-transfected cells was displaced completely by chemokines that bind to these receptors. Both CCR1- and CCR2B-transfected 293 cells showed significant migration in response to MCP-2, in addition to responding to other specific chemokines. These results clearly demonstrate that MCP-2, unlike MCP-1, uses both CCR1 as well as CCR2B as its functional receptors, and this accounts for the unique activities of MCP-2.
单核细胞趋化蛋白（MCP）-2是C-C趋化因子亚家族的一员，它与MCP-1和MCP-3的序列同源性超过60%，与巨噬细胞炎性蛋白（MIP）-1α、正常T细胞表达和分泌调节因子（RANTES）以及MIP-1β的同源性约为30%。尽管与其他C-C趋化因子有相当高的序列同源性，但与MCP-1和MCP-3等其他C-C趋化因子相比，MCP-2似乎具有独特的功能特性。虽然从白细胞研究中获得的证据表明MCP-2可能与这些C-C趋化因子共用受体，但MCP-2的实际功能受体尚未确定。在本研究中，我们使用放射性碘化的MCP-2，在人外周血单核细胞上鉴定出了MCP-2的高亲和力结合位点。MCP-1和MCP-3可竞争MCP-2的结合，但MIP-1α或RANTES的竞争较弱。在使用转染了C-C趋化因子受体的细胞进行的实验中，125I-MCP-2与转染了CCR1或CCR2B的人胚肾293细胞结合，已知CCR1和CCR2B分别还与MIP-1α/RANTES和MCP-1结合，但MCP-3与它们都有共享。与这些受体结合的趋化因子可完全取代125I-MCP-2与这些受体转染细胞的结合。除了对其他特定趋化因子有反应外，转染了CCR1和CCR2B的293细胞对MCP-2也有明显的迁移反应。这些结果清楚地表明，与MCP-1不同，MCP-2同时使用CCR1和CCR2B作为其功能受体，这解释了MCP-2的独特活性。
