Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37240, USA.
Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY 40536, USA.
J Cell Sci. 2023 Jul 15;136(14). doi: 10.1242/jcs.260675. Epub 2023 Jul 25.
Accumulating evidence in several model organisms indicates that reduced sphingolipid biosynthesis promotes longevity, although underlying mechanisms remain unclear. In yeast, sphingolipid depletion induces a state resembling amino acid restriction, which we hypothesized might be due to altered stability of amino acid transporters at the plasma membrane. To test this, we measured surface abundance for a diverse panel of membrane proteins in the presence of myriocin, a sphingolipid biosynthesis inhibitor, in Saccharomyces cerevisiae. Unexpectedly, we found that surface levels of most proteins examined were either unaffected or increased during myriocin treatment, consistent with an observed decrease in bulk endocytosis. In contrast, sphingolipid depletion triggered selective endocytosis of the methionine transporter Mup1. Unlike methionine-induced Mup1 endocytosis, myriocin triggered Mup1 endocytosis that required the Rsp5 adaptor Art2, C-terminal lysine residues of Mup1 and the formation of K63-linked ubiquitin polymers. These findings reveal cellular adaptation to sphingolipid depletion by ubiquitin-mediated remodeling of nutrient transporter composition at the cell surface.
越来越多的证据表明，在几种模式生物中，减少鞘脂生物合成可促进长寿，尽管其潜在机制尚不清楚。在酵母中，鞘脂耗竭诱导出一种类似于氨基酸限制的状态，我们假设这可能是由于质膜上氨基酸转运体的稳定性发生改变。为了验证这一点，我们在酿酒酵母中测量了有丝分裂原（一种鞘脂生物合成抑制剂）存在时，多种膜蛋白的表面丰度。出乎意料的是，我们发现大多数检测到的蛋白质的表面水平在有丝分裂原处理期间要么不受影响，要么增加，这与整体内吞作用的观察到的下降一致。相比之下，鞘脂耗竭会触发甲硫氨酸转运蛋白 Mup1 的选择性内吞作用。与甲硫氨酸诱导的 Mup1 内吞作用不同，有丝分裂原触发的 Mup1 内吞作用需要 Rsp5 衔接蛋白 Art2、Mup1 的 C 末端赖氨酸残基和 K63 连接的泛素聚合物的形成。这些发现揭示了细胞通过泛素介导的对营养物转运蛋白组成的重塑来适应鞘脂耗竭。
