Department of Biology, University of Fribourg, 1700 Fribourg, Switzerland.
Department of Epidemiology, Preclinical Research and Advanced Diagnostics, National Institute for Infectious Diseases IRCCS "L. Spallanzani", 00149 Rome, Italy; Department of Pharmacology, Federal University of São Paulo (UNIFESP), São Paulo CEP 05508-000, Brazil.
Cell Rep. 2024 Sep 24;43(9):114689. doi: 10.1016/j.celrep.2024.114689. Epub 2024 Aug 27.
Autophagy initiation is regulated by the ULK1 kinase complex. To gain insights into functions of the holo-complex, we generated a deep interactome by combining affinity purification- and proximity labeling-mass spectrometry of all four complex members: ULK1, ATG13, ATG101, and RB1CC1/FIP200. Under starvation conditions, the ULK1 complex interacts with several protein and lipid kinases and phosphatases, implying the formation of a signalosome. Interestingly, several selective autophagy receptors also interact with ULK1, indicating the activation of selective autophagy pathways by nutrient starvation. One effector of the ULK1 complex is the HSC/HSP70 co-chaperone BAG2, which regulates the subcellular localization of the VPS34 lipid kinase complex member AMBRA1. Depending on the nutritional status, BAG2 has opposing roles. In growth conditions, the unphosphorylated form of BAG2 sequesters AMBRA1, attenuating autophagy induction. In starvation conditions, ULK1 phosphorylates BAG2 on Ser31, which supports the recruitment of AMBRA1 to the ER membrane, positively affecting autophagy.
自噬的起始受到 ULK1 激酶复合物的调控。为了深入了解该全酶复合物的功能，我们通过对四个复合物成员（ULK1、ATG13、ATG101 和 RB1CC1/FIP200）进行亲和纯化和邻近标记质谱分析，构建了一个深度互作组。在饥饿条件下，ULK1 复合物与几种蛋白和脂质激酶及磷酸酶相互作用，表明形成了一个信号体。有趣的是，几种选择性自噬受体也与 ULK1 相互作用，表明营养饥饿激活了选择性自噬途径。ULK1 复合物的一个效应因子是 HSP70 共伴侣 BAG2，它调节 VPS34 脂质激酶复合物成员 AMBRA1 的亚细胞定位。根据营养状况，BAG2 具有相反的作用。在生长条件下，非磷酸化形式的 BAG2 隔离 AMBRA1，从而减弱自噬的诱导。在饥饿条件下，ULK1 磷酸化 BAG2 的 Ser31 位，促进 AMBRA1 募集到内质网膜上，从而正向影响自噬。
