Department of Neurology and Neurosurgery, Montreal Neurological Institute (the Neuro), McGill University, Montreal, QC, Canada.
Nat Commun. 2024 Jan 31;15(1):919. doi: 10.1038/s41467-024-44957-1.
Lysosomes help maintain cellular proteostasis, and defects in lysosomal positioning and function can cause disease, including neurodegenerative disorders. The spatiotemporal distribution of lysosomes is regulated by small GTPases including Rabs, which are activated by guanine nucleotide exchange factors (GEFs). DENN domain proteins are the largest family of Rab GEFs. Using a cell-based assay, we screened DENND6A, a member of the DENN domain protein family against all known Rabs and identified it as a potential GEF for 20 Rabs, including Rab34. Here, we demonstrate that DENND6A activates Rab34, which recruits a RILP/dynein complex to lysosomes, promoting lysosome retrograde transport. Further, we identify DENND6A as an effector of Arl8b, a major regulatory GTPase on lysosomes. We demonstrate that Arl8b recruits DENND6A to peripheral lysosomes to activate Rab34 and initiate retrograde transport, regulating nutrient-dependent lysosomal juxtanuclear repositioning. Loss of DENND6A impairs autophagic flux. Our findings support a model whereby Arl8b/DENND6A/Rab34-dependent lysosomal retrograde trafficking controls autophagy.
溶酶体有助于维持细胞内蛋白质平衡，溶酶体定位和功能的缺陷可导致疾病，包括神经退行性疾病。溶酶体的时空分布受小 GTPase 调节，包括被鸟嘌呤核苷酸交换因子 (GEF) 激活的 Rabs。DENN 结构域蛋白是 Rab GEF 中最大的家族。我们使用基于细胞的测定方法筛选了 DENND6A，这是 DENN 结构域蛋白家族的成员，用于筛选所有已知的 Rab，并将其鉴定为 20 个 Rab（包括 Rab34）的潜在 GEF。在这里，我们证明 DENND6A 激活 Rab34，后者招募 RILP/动力蛋白复合物到溶酶体上，促进溶酶体逆行运输。此外，我们将 DENND6A 鉴定为 Arl8b 的效应物，Arl8b 是溶酶体上的主要调节 GTPase。我们证明 Arl8b 将 DENND6A 募集到周边溶酶体以激活 Rab34 并启动逆行运输，从而调节营养依赖性溶酶体核周再定位。DENND6A 的缺失会损害自噬通量。我们的研究结果支持以下模型，即 Arl8b/DENND6A/Rab34 依赖性溶酶体逆行运输控制自噬。
