Department of Biology, York University, 4700 Keele Street, Toronto, M3J 1P3, ON, Canada.
Department of Chemistry, York University, 4700 Keele Street, Toronto, M3J 1P3, ON, Canada.
Commun Biol. 2020 Nov 13;3(1):672. doi: 10.1038/s42003-020-01397-z.
Hematopoietic adaptor containing SH3 and SAM domains-1 (HACS1) is a signaling protein with two juxtaposed protein-protein interaction domains and an intrinsically unstructured region that spans half the sequence. Here, we describe the interaction between the HACS1 SH3 domain and a sequence near the third immunoreceptor tyrosine-based inhibition motif (ITIM3) of the paired immunoglobulin receptor B (PIRB). From surface plasmon resonance binding assays using a mouse and human PIRB ITIM3 phosphopeptides as ligands, the HACS1 SH3 domain and SHP2 N-terminal SH2 domain demonstrated comparable affinities in the micromolar range. Since the PIRB ITIM3 sequence represents an atypical ligand for an SH3 domain, we determined the NMR structure of the HACS1 SH3 domain and performed a chemical shift mapping study. This study showed that the binding site on the HACS1 SH3 domain for PIRB shares many of the same amino acids found in a canonical binding cleft normally associated with polyproline ligands. Molecular modeling suggests that the respective binding sites in PIRB ITIM3 for the HACS1 SH3 domain and the SHP2 SH2 domain are too close to permit simultaneous binding. As a result, the HACS1-PIRB partnership has the potential to amalgamate signaling pathways that influence both immune and neuronal cell fate.
造血衔接蛋白 SH3 和 SAM 结构域-1（HACS1）是一种信号蛋白，具有两个毗邻的蛋白-蛋白相互作用结构域和一个横跨序列一半的固有无规卷曲区域。在这里，我们描述了 HACS1 SH3 结构域与配对免疫球蛋白受体 B（PIRB）的第三个免疫受体酪氨酸抑制基序（ITIM3）附近序列之间的相互作用。从使用作为配体的小鼠和人 PIRB ITIM3 磷酸肽的表面等离子体共振结合测定中，HACS1 SH3 结构域和 SHP2 N 端 SH2 结构域在微摩尔范围内表现出可比的亲和力。由于 PIRB ITIM3 序列代表了 SH3 结构域的非典型配体，我们确定了 HACS1 SH3 结构域的 NMR 结构并进行了化学位移映射研究。该研究表明，HACS1 SH3 结构域与 PIRB 结合的结合位点共享许多与通常与多聚脯氨酸配体相关的典型结合裂缝中相同的氨基酸。分子建模表明，HACS1 SH3 结构域和 SHP2 SH2 结构域在 PIRB ITIM3 中的各自结合位点彼此过于接近，以致不能同时结合。因此，HACS1-PIRB 伙伴关系有可能合并影响免疫和神经元细胞命运的信号通路。
