Schraufstätter I U, Burger M, Hoch R C, Oades Z G, Takamori H
Department of Immunology, Scripps Research Institute, La Jolla, California 92037, USA.
Biochem Biophys Res Commun. 1998 Mar 6;244(1):243-8. doi: 10.1006/bbrc.1998.8246.
The CXCR2 is phosphorylated at the C-terminal intracytoplasmic portion within 15 sec following the addition of IL-8 or MGSA. Cells transfected with a truncated form of the receptor missing the last 12 amino acids (T3) showed normal binding affinity, but were no longer phosphorylated; individual alanine replacement indicated that Ser346 and 348 were the primary sites of phosphorylation. In studies of the importance of phosphorylation in CXCR2 desensitization, cells expressing wild type CXCR2 lost GTP gamma S binding above basal rate after the first exposure to IL-8, while cells with the T3 mutant retained 60% of their capacity to induce GTP gamma S exchange upon a second exposure to IL-8. In contrast, receptor internalization was not affected by the loss of phosphorylation of the T3 mutant. Further receptor truncation led to decreasing binding affinities for IL-8 and MGSA and a decreased rate of GTP gamma S exchange following addition of excess ligand which suggests involvement of this region in G-protein coupling.
在添加白细胞介素-8（IL-8）或黑色素生长刺激活性因子（MGSA）后的15秒内，CXC趋化因子受体2（CXCR2）在其C端胞质内部分发生磷酸化。用缺失最后12个氨基酸的受体截短形式（T3）转染的细胞表现出正常的结合亲和力，但不再发生磷酸化；单个丙氨酸替代表明，丝氨酸346和348是磷酸化的主要位点。在关于磷酸化在CXCR2脱敏中的重要性的研究中，表达野生型CXCR2的细胞在首次暴露于IL-8后，其高于基础水平的GTPγS结合能力丧失，而具有T3突变体的细胞在第二次暴露于IL-8时仍保留60%的诱导GTPγS交换的能力。相比之下，受体内化不受T3突变体磷酸化缺失的影响。进一步的受体截短导致对IL-8和MGSA的结合亲和力降低，以及在添加过量配体后GTPγS交换速率降低，这表明该区域参与了G蛋白偶联。
