Department of Biology, University of Fribourg, Chemin du Musée 10, 1700 Fribourg, Switzerland.
Department of Biology, University of Fribourg, Chemin du Musée 10, 1700 Fribourg, Switzerland
Biol Open. 2020 Jul 2;9(6):bio053470. doi: 10.1242/bio.053470.
Members of the CAP/SCP/TAPS superfamily have been implicated in many different physiological processes, including pathogen defense, sperm maturation and fertilization. The mode of action of this class of proteins, however, remains poorly understood. The genome of encodes three CAP superfamily members, Pry1-3. We have previously shown that Pry1 function is required for the secretion of sterols and fatty acids. Here, we analyze the function of Pry3, a GPI-anchored cell wall protein. Overexpression of Pry3 results in strong reduction of mating efficiency, providing for a cell-based readout for CAP protein function. Mating inhibition is a conserved function of the CAP domain and depends on highly conserved surface exposed residues that form part of a putative catalytic metal-ion binding site. Pry3 displays polarized cell surface localization adjacent to bud scars, but is absent from mating projections. When overexpressed, however, the protein leaks onto mating projections, suggesting that mating inhibition is due to mislocalization of the protein. Trapping of the CAP domain within the cell wall through a GPI-anchored nanobody results in a dose-dependent inhibition of mating, suggesting that a membrane proximal CAP domain inhibits a key step in the mating reaction, which is possibly related to the function of CAP domain proteins in mammalian fertilization.This article has an associated First Person interview with the first author of the paper.
CAP/SCP/TAPS 超家族的成员参与了许多不同的生理过程，包括病原体防御、精子成熟和受精。然而，这类蛋白质的作用模式仍知之甚少。编码三个 CAP 超家族成员，Pry1-3。我们之前已经表明，Pry1 的功能对于固醇和脂肪酸的分泌是必需的。在这里，我们分析了 Pry3 的功能，Pry3 是一种糖基磷脂酰肌醇锚定的细胞壁蛋白。Pry3 的过表达导致交配效率的强烈降低，为 CAP 蛋白功能提供了基于细胞的读出。交配抑制是 CAP 结构域的保守功能，取决于高度保守的表面暴露残基，这些残基构成了假定的催化金属离子结合位点的一部分。Pry3 显示出与芽痕相邻的极化细胞表面定位，但不存在于交配突起中。然而，当过表达时，该蛋白会泄漏到交配突起上，表明交配抑制是由于蛋白的错误定位。通过糖基磷脂酰肌醇锚定纳米体将 CAP 结构域困在细胞壁内，会导致交配的剂量依赖性抑制，这表明膜近端 CAP 结构域抑制了交配反应中的一个关键步骤，这可能与 CAP 结构域蛋白在哺乳动物受精中的功能有关。本文有一篇与该论文第一作者的相关第一人称采访。
