Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, IL 60607-7170, USA.
J Cell Sci. 2021 Apr 15;134(8). doi: 10.1242/jcs.247833. Epub 2021 Apr 22.
GPR15 is a G-protein-coupled receptor (GPCR) that directs lymphocyte homing to the colon and skin. Recent studies have identified a chemokine-like protein GPR15L (also known as C10orf99) as a functional ligand of GPR15. In this study, we examined the structural elements that regulate the GPR15-GPR15L interaction with primary focus on post-translational modifications (PTMs) of receptor N-terminus and on the C-terminus of the ligand. Our findings reveal that the GPR15 receptor is sulfated on the N-terminal tyrosine residue(s) and disruption of tyrosine sulfation inhibits binding of GPR15L. In contrast, the disruption of O-glycosylation on the N-terminal threonine or serine residues, or the removal of α2,3-linked sialic acids from O-glycans, enhances the GPR15L binding. Thus, GPR15 represents a unique chemoattractant receptor in which different N-terminal PTMs regulate its ligand binding in a contrasting manner. We further demonstrate that, unlike canonical chemokines, GPR15L activity critically requires its extreme C-terminal residue and that its hydrophobicity may be a key attribute that facilitates an optimal interaction with the receptor. Our results reveal novel insights into chemoattractant receptor-ligand interaction and provide a valid footing for potential intervention targeting the GPR15-GPR15L axis.
GPR15 是一种 G 蛋白偶联受体 (GPCR)，可引导淋巴细胞归巢至结肠和皮肤。最近的研究鉴定出一种趋化因子样蛋白 GPR15L（也称为 C10orf99）是 GPR15 的功能性配体。在这项研究中，我们研究了调节 GPR15-GPR15L 相互作用的结构元件，主要关注受体 N 端的翻译后修饰 (PTM) 和配体的 C 端。我们的研究结果表明，GPR15 受体在 N 端酪氨酸残基上发生硫酸化，酪氨酸硫酸化的破坏抑制了 GPR15L 的结合。相比之下，破坏 N 端苏氨酸或丝氨酸上的 O-糖基化，或从 O-聚糖中去除α2,3 连接的唾液酸，会增强 GPR15L 的结合。因此，GPR15 代表了一种独特的趋化因子受体，其中不同的 N 端 PTM 以相反的方式调节其配体结合。我们进一步证明，与典型的趋化因子不同，GPR15L 的活性严重依赖于其极端的 C 端残基，其疏水性可能是促进与受体最佳相互作用的关键属性。我们的研究结果揭示了趋化因子受体-配体相互作用的新见解，并为针对 GPR15-GPR15L 轴的潜在干预提供了有效的基础。
