Key Laboratory of Immune Microenvironment and Disease (Ministry of Education), Tianjin Institute of Immunology, the Province and Ministry Co-Sponsored Collaborative Innovation Center for Medical Epigenetics, Department of Immunology, School of Basic Medical Sciences, Tianjin Institute of Urology, The Second Hospital of Tianjin Medical University, Tianjin, China.
Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Tianjin Medical University, Tianjin, China.
Autophagy. 2023 Oct;19(10):2702-2718. doi: 10.1080/15548627.2023.2223468. Epub 2023 Jun 13.
HSPA8 (heat shock protein family A (Hsp70) member 8) plays a significant role in the autophagic degradation of proteins, however, its effect on protein stabilization and anti-bacterial autophagy remains unknown. Here, it is discovered that HSPA8, as a binding partner of RHOB and BECN1, induce autophagy for intracellular bacteria clearance. Using its NBD and LID domains, HSPA8 physically binds to RHOB residues 1-42 and 89-118 as well as to BECN1 ECD domain, preventing RHOB and BECN1 degradation. Intriguingly, HSPA8 contains predicted intrinsically disordered regions (IDRs), and drives liquid-liquid phase separation (LLPS) to concentrate RHOB and BECN1 into HSPA8-formed liquid-phase droplets, resulting in improved RHOB and BECN1 interactions. Our study reveals a novel role and mechanism of HSPA8 in modulating anti-bacterial autophagy, and highlights the effect of LLPS-related HSPA8-RHOB-BECN1 complex on enhancing protein interaction and stabilization, which improves the understanding of autophagy-mediated defense against bacteria.
HSPA8（热休克蛋白家族 A（Hsp70）成员 8）在蛋白质的自噬降解中发挥重要作用，但其对蛋白质稳定和抗细菌自噬的影响尚不清楚。在这里，研究发现 HSPA8 作为 RHOB 和 BECN1 的结合伴侣，诱导自噬以清除细胞内细菌。HSPA8 通过其 NBD 和 LID 结构域，与 RHOB 的残基 1-42 和 89-118 以及 BECN1 的 ECD 结构域物理结合，从而防止 RHOB 和 BECN1 的降解。有趣的是，HSPA8 含有预测的无规卷曲区域（IDR），并通过液-液相分离（LLPS）将 RHOB 和 BECN1 浓缩到 HSPA8 形成的液相液滴中，从而增强了 RHOB 和 BECN1 的相互作用。本研究揭示了 HSPA8 在调节抗细菌自噬中的新作用和机制，并强调了与 LLPS 相关的 HSPA8-RHOB-BECN1 复合物对增强蛋白质相互作用和稳定性的影响，从而加深了对自噬介导的细菌防御的理解。
