The Wellcome Centre for Integrative Parasitology, School of Infection & Immunity, University of Glasgow, Glasgow, UK.
Department of Cell and Molecular Biology, Ribeirão Preto Medical School, University of São Paulo, São Paulo, Brazil.
J Eukaryot Microbiol. 2023 Nov-Dec;70(6):e12994. doi: 10.1111/jeu.12994. Epub 2023 Aug 7.
Selection and internalization of cargo via clathrin-mediated endocytosis requires adaptor protein complexes. One complex, AP-2, acts during cargo selection at the plasma membrane. African trypanosomes lack all components of the AP-2 complex, except for a recently identified orthologue of the AP-2-associated protein kinase 1, AAK1. In characterized eukaryotes, AAK1 phosphorylates the μ2 subunit of the AP-2 complex to enhance cargo recognition and uptake into clathrin-coated vesicles. Here, we show that kinetoplastids encode not one, but two AAK1 orthologues: one (AAK1L2) is absent from salivarian trypanosomes, while the other (AAK1L1) lacks important kinase-specific residues in a range of trypanosomes. These AAK1L1 and AAK1L2 novelties reinforce suggestions of functional divergence in endocytic uptake within salivarian trypanosomes. Despite this, we show that AAK1L1 null mutant Trypanosoma brucei, while viable, display slowed proliferation, morphological abnormalities including swelling of the flagellar pocket, and altered cargo uptake. In summary, our data suggest an unconventional role for a putative pseudokinase during endocytosis and/or vesicular trafficking in T. brucei, independent of AP-2.
通过网格蛋白介导的内吞作用选择和内化货物需要衔接蛋白复合物。一个复合物 AP-2 在质膜上的货物选择过程中起作用。非洲锥虫缺乏 AP-2 复合物的所有成分，除了最近鉴定的 AP-2 相关蛋白激酶 1（AAK1）的同源物。在已鉴定的真核生物中，AAK1 磷酸化 AP-2 复合物的 μ2 亚基，以增强货物的识别和摄取到网格蛋白包被的小泡中。在这里，我们表明，动基体门原生动物编码的不是一个，而是两个 AAK1 同源物：一个（AAK1L2）在唾液生物锥虫中缺失，而另一个（AAK1L1）在一系列锥虫中缺乏重要的激酶特异性残基。这些 AAK1L1 和 AAK1L2 的新颖性加强了在唾液生物锥虫中内吞作用吸收的功能分化的建议。尽管如此，我们表明 AAK1L1 缺失突变型 Trypanosoma brucei 虽然存活，但增殖缓慢，形态异常，包括鞭毛囊肿胀，以及货物摄取改变。总之，我们的数据表明，在 T. brucei 中，一种假定的拟激酶在胞吞作用和/或囊泡运输中可能具有非传统作用，而与 AP-2 无关。
