School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, U.S.A.
Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390, U.S.A.
Biosci Rep. 2024 Oct 30;44(10). doi: 10.1042/BSR20240200.
GABARAP is a member of the ATG8 family of ubiquitin-like autophagy related proteins. It was initially discovered as a facilitator of GABA-A receptor translocation to the plasma membrane and has since been shown to promote the intracellular transport of a variety of other proteins under non-autophagic conditions. We and others have shown that GABARAP interacts with the Type II phosphatidylinositol 4-kinase, PI4K2A, and that this interaction is important for autophagosome-lysosome fusion. Here, we identify a 7-amino acid segment within the PI4K2A catalytic domain that contains the GABARAP interaction motif (GIM). This segment resides in an exposed loop that is not conserved in the other mammalian Type II PI 4-kinase, PI4K2B, explaining the specificity of GABARAP binding to the PI4K2A isoform. Mutation of the PI4K2A GIM inhibits GABARAP binding and PI4K2A-mediated recruitment of cytosolic GABARAP to subcellular organelles. We further show that GABARAP binds to mono-phosphorylated phosphoinositides, PI3P, PI4P, and PI5P, raising the possibility that these lipids contribute to the binding energies that drive GABARAP-protein interactions on membranes.
GABARAP 是泛素样自噬相关蛋白 ATG8 家族的成员。它最初被发现是 GABA-A 受体易位到质膜的促进因子，此后已被证明在非自噬条件下促进多种其他蛋白质的细胞内运输。我们和其他人已经表明，GABARAP 与 II 型磷酸肌醇 4-激酶（PI4K2A）相互作用，并且这种相互作用对于自噬体-溶酶体融合很重要。在这里，我们确定了 PI4K2A 催化结构域内的一个 7 个氨基酸片段，该片段包含 GABARAP 相互作用基序（GIM）。该片段位于暴露的环中，在其他哺乳动物 II 型 PI4-激酶 PI4K2B 中不保守，这解释了 GABARAP 与 PI4K2A 同工型特异性结合的原因。PI4K2A GIM 的突变抑制 GABARAP 结合和 PI4K2A 介导的将胞质 GABARAP 募集到亚细胞器。我们进一步表明，GABARAP 结合单磷酸化的磷酸肌醇，PI3P、PI4P 和 PI5P，这增加了这些脂质有助于驱动膜上 GABARAP-蛋白相互作用的结合能的可能性。
