Analysis of CS5 co-receptor molecule that specifically inhibits chemotaxis of polymorphonuclear leukocytes

RP S19的交联二聚体作为C5a受体的激动剂吸引单核细胞。另一方面，该分子作为C5a受体拮抗剂抑制多形核白细胞（PMN）的趋化性。我们最初确定了RP S19二聚体与单核细胞C5a受体的配体部分。RP S19二聚体通过两步机制与C5a受体结合。第一配体和第二配体分别为lys41 - his42 - lys43 -和- leu131 - asp132 - arg133 -。接下来，我们确定了RPS19二聚体分子上的一个开关片段，该片段在C5a受体介导的PMN趋化性中将激动剂功能转化为拮抗剂。该开关片段位于Ile134到Lys144 （IAGQVAAANKK）之间，位于第二配体片段之后。我们假设PMN在C5a受体附近有一个分子，该分子负向调节被激活的C5a受体引起的细胞内信号。然后我们一直在尝试识别共受体分子。我们在PMN cDNA库和单核细胞cDNA库之间准备了一个减法cDNA文库。我们试图制备具有第二配体片段和带有荧光标记光敏化学修饰剂的开关片段的类似肽。然而，我们尚未成功地鉴定出PMN C5a受体的共受体分子。

The cross-linked dimer of RP S19 attracted monocytes as an agonist of C5a receptor. On the other hand, the same molecule inhibited the chemotaxis of polymorphonuclear leukocytes (PMN) as an antagonist of the C5a receptor. We initially identified the ligand moieties of the RP S19 dimer to the C5a receptor of monocytes. The RP S19 dimer bound to the C5a receptor by a two-step mechanism. The first ligand and second ligand moieties were identified to be-Lys41-His42-Lys43- and -Leu131-Asp132-Arg133-, respectively.Next, we identified a switch moiety on the RPS19 dimer molecule, which converted the agonist function to the antagonist in the C5a receptor-mediated chemotaxis of PMN. The switch moiety was identified to be from Ile134 to Lys144 (IAGQVAAANKK), which was present following to the second ligand moiety.We made a hypothesis that PMN had a molecule near the C5a receptor, which negatively regulated the intracellular signaling raised by the activated C5a receptor. Then we have been trying to identify the co-receptor molecule. We have prepared a subtraction cDNA library between a PMN cDNA pool and a monocyte cDNA pool. We have tried to prepare an analogue peptide with the second ligand moiety and the switch moiety that bore a fluorescence-labeled photosensitive chemical modifier. However, we have not succeeded to identify the co-receptor molecule of the PMN C5a receptor.