CXCR3 requires tyrosine sulfation for ligand binding and a second extracellular loop arginine residue for ligand-induced chemotaxis
CXCR3 requires tyrosine sulfation for ligand binding and a second extracellular loop arginine residue for ligand-induced chemotaxis
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DOI：
10.1128/mcb.00556-06
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发表时间：
2006-08-01
影响因子：
5.3
通讯作者：
Luster, Andrew D.
中科院分区：
文献类型：
--
作者：
Colvin, Richard A.;Campanella, Gabriele S. V.;Luster, Andrew D.
CXCR3 是一种 G 蛋白偶联七跨膜结构域趋化因子受体，在效应 T 细胞和 NK 细胞运输中发挥重要作用。三种 γ 干扰素诱导趋化因子可激活 CXCR3：CXCL9 (Mig)、CXCL10 (IP-10) 和 CXCL11 (I-TAC)。在这里，我们鉴定了配体结合和激活所需的 CXCR3 胞外结构域。我们发现 CXCR3 在其 N 末端被硫酸化，并且所有三个配体的结合和激活都需要硫酸化。我们还发现，N 末端的近 16 个氨基酸残基是 CXCL10 和 CXCL11 结合和激活所必需的，但不是 CXCL9 激活所必需的。此外，我们发现第二个细胞外环中的残基8216是CXCR3介导的趋化性和钙动员所必需的，但不是配体结合或配体诱导的CXCR3内化所必需的。最后，细胞外环中的带电残基有助于受体-配体相互作用。这些发现表明，CXCR3 的趋化因子激活涉及与 CXCR3 胞外结构域中带负电残基的高亲和力配体结合相互作用，以及第二胞外环中的低亲和力受体激活相互作用。这种较低亲和力的相互作用是诱导趋化性所必需的，但不是配体诱导的 CXCR3 内化所必需的，这进一步表明 CXCR3 的不同结构域介导不同的功能。
CXCR3 is a G-protein-coupled seven-transmembrane domain chemokine receptor that plays an important role in effector T-cell and NK cell trafficking. Three gamma interferon-inducible chemokines activate CXCR3: CXCL9 (Mig), CXCL10 (IP-10), and CXCL11 (I-TAC). Here, we identify extracellular domains of CXCR3 that are required for ligand binding and activation. We found that CXCR3 is sulfated on its N terminus and that sulfation is required for binding and activation by all three ligands. We also found that the proximal 16 amino acid residues of the N terminus are required for CXCL10 and CXCL11 binding and activation but not CXCL9 activation. In addition, we found that residue 8216 in the second extracellular loop is required for CXCR3-mediated chemotaxis and calcium mobilization but is not required for ligand binding or ligand-induced CXCR3 internalization. Finally, charged residues in the extracellular loops contribute to the receptor-ligand interaction. These findings demonstrate that chemokine activation of CXCR3 involves both high-affinity ligand-binding interactions with negatively charged residues in the extracellular domains of CXCR3 and a lower-affinity receptor-activating interaction in the second extracellular loop. This lower-affinity interaction is necessary to induce chemotaxis but not ligand-induced CXCR3 internalization, further suggesting that different domains of CXCR3 mediate distinct functions.