Hegedűs Krisztina, Nagy Péter, Gáspári Zoltán, Juhász Gábor
Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, Budapest 1117, Hungary.
Faculty of Information Technology and Bionics, Pázmány Péter Catholic University, Budapest 1083, Hungary.
Biomed Res Int. 2014;2014:470482. doi: 10.1155/2014/470482. Epub 2014 May 8.
The large-scale turnover of intracellular material including organelles is achieved by autophagy-mediated degradation in lysosomes. Initiation of autophagy is controlled by a protein kinase complex consisting of an Atg1-family kinase, Atg13, FIP200/Atg17, and the metazoan-specific subunit Atg101. Here we show that loss of Atg101 impairs both starvation-induced and basal autophagy in Drosophila. This leads to accumulation of protein aggregates containing the selective autophagy cargo ref(2)P/p62. Mapping experiments suggest that Atg101 binds to the N-terminal HORMA domain of Atg13 and may also interact with two unstructured regions of Atg1. Another HORMA domain-containing protein, Mad2, forms a conformational homodimer. We show that Drosophila Atg101 also dimerizes, and it is predicted to fold into a HORMA domain. Atg101 interacts with ref(2)P as well, similar to Atg13, Atg8a, Atg16, Atg18, Keap1, and RagC, a known regulator of Tor kinase which coordinates cell growth and autophagy. These results raise the possibility that the interactions and dimerization of the putative HORMA domain protein Atg101 play critical roles in starvation-induced autophagy and proteostasis, by promoting the formation of protein aggregate-containing autophagosomes.
包括细胞器在内的细胞内物质的大规模周转是通过溶酶体中自噬介导的降解来实现的。自噬的起始由一种蛋白激酶复合物控制，该复合物由Atg1家族激酶、Atg13、FIP200/Atg17和后生动物特异性亚基Atg101组成。在这里，我们表明Atg101的缺失会损害果蝇中饥饿诱导的自噬和基础自噬。这导致含有选择性自噬货物ref(2)P/p62的蛋白质聚集体的积累。定位实验表明，Atg101与Atg13的N端HORMA结构域结合，也可能与Atg1的两个无结构区域相互作用。另一种含有HORMA结构域的蛋白质Mad2形成构象同源二聚体。我们表明果蝇Atg101也会二聚化，并且预计会折叠成一个HORMA结构域。Atg101也与ref(2)P相互作用，类似于Atg13、Atg8a、Atg16、Atg18、Keap1和RagC，RagC是一种已知的协调细胞生长和自噬的Tor激酶调节剂。这些结果增加了一种可能性，即假定的HORMA结构域蛋白Atg101的相互作用和二聚化通过促进含蛋白质聚集体的自噬体的形成，在饥饿诱导的自噬和蛋白质稳态中发挥关键作用。
