School of Biochemistry and Immunology, Trinity College, Dublin 2, Ireland.
MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life Sciences, University of Dundee, Dundee, UK.
Structure. 2020 Apr 7;28(4):406-417.e6. doi: 10.1016/j.str.2020.01.005. Epub 2020 Feb 3.
Rab8a is associated with the dynamic regulation of membrane protrusions in polarized cells. Rab8a is one of several Rab GTPases that are substrates of leucine-rich repeat kinase 2 (LRRK2), a serine/threonine kinase that is linked to Parkinson's disease. Rab8a is phosphorylated at T72 (pT72) in its switch 2 helix and recruits the phospho-specific effector RILPL2, which subsequently regulates ciliogenesis. Here, we report the crystal structure of phospho-Rab8a (pRab8a) in complex with the RH2 (RILP homology) domain of RILPL2. The complex is a heterotetramer with RILPL2 forming a central α-helical dimer that bridges two pRab8a molecules. The N termini of the α helices cross over, forming an X-shaped cap (X-cap) that orients Arg residues from RILPL2 toward pT72. X-cap residues critical for pRab8a binding are conserved in JIP3 and JIP4, which also interact with LRRK2-phosphorylated Rab10. We propose a general mode of recognition for phosphorylated Rab GTPases by this family of phospho-specific effectors.
Rab8a 与极化细胞中膜突的动态调节有关。Rab8a 是几个 Rab GTPases 之一，是富含亮氨酸重复激酶 2 (LRRK2) 的底物，LRRK2 是一种丝氨酸/苏氨酸激酶，与帕金森病有关。Rab8a 在其开关 2 螺旋中的 T72 位点 (pT72) 磷酸化，招募磷酸特异性效应因子 RILPL2，随后调节纤毛发生。在这里，我们报告了磷酸化 Rab8a (pRab8a) 与 RILPL2 的 RH2 (RILP 同源) 结构域复合物的晶体结构。该复合物是一个异四聚体，其中 RILPL2 形成一个中央 α 螺旋二聚体，桥接两个 pRab8a 分子。α 螺旋的 N 端交叉，形成一个 X 形帽 (X-cap)，将来自 RILPL2 的 Arg 残基定向到 pT72。对于 pRab8a 结合至关重要的 X-cap 残基在 JIP3 和 JIP4 中保守，它们也与 LRRK2 磷酸化的 Rab10 相互作用。我们提出了这个磷酸特异性效应因子家族识别磷酸化 Rab GTPases 的一般模式。
