Department of Biology, Texas A&M University, College Station, TX 77843-3474, USA.
J Cell Sci. 2022 Sep 15;135(18). doi: 10.1242/jcs.260107. Epub 2022 Sep 21.
Dictyostelium discoideum is a unicellular eukaryote that eats bacteria, and eventually outgrows the bacteria. D. discoideum cells accumulate extracellular polyphosphate (polyP), and the polyP concentration increases as the local cell density increases. At high cell densities, the correspondingly high extracellular polyP concentrations allow cells to sense that they are about to outgrow their food supply and starve, causing the D. discoideum cells to inhibit their proliferation. In this report, we show that high extracellular polyP inhibits exocytosis of undigested or partially digested nutrients. PolyP decreases plasma membrane recycling and apparent cell membrane fluidity, and this requires the G protein-coupled polyP receptor GrlD, the polyphosphate kinase Ppk1 and the inositol hexakisphosphate kinase I6kA. PolyP alters protein contents in detergent-insoluble crude cytoskeletons, but does not significantly affect random cell motility, cell speed or F-actin levels. Together, these data suggest that D. discoideum cells use polyP as a signal to sense their local cell density and reduce cell membrane fluidity and membrane recycling, perhaps as a mechanism to retain ingested food when the cells are about to starve. This article has an associated First Person interview with the first author of the paper.
黏菌（Dictyostelium discoideum）是一种可食用细菌的单细胞真核生物，最终会生长到细菌无法满足其生长需求的程度。黏菌细胞会积累细胞外多聚磷酸盐（polyP），并且随着局部细胞密度的增加，polyP 浓度也会增加。在高细胞密度下，相应的高细胞外多聚磷酸盐浓度会使细胞意识到它们即将耗尽食物供应而饥饿，从而导致黏菌细胞抑制其增殖。在本报告中，我们表明高细胞外多聚磷酸盐会抑制未消化或部分消化的营养物质的胞吐作用。多聚磷酸盐会降低质膜的循环利用和明显的细胞膜流动性，这需要 G 蛋白偶联的多聚磷酸盐受体 GrlD、多聚磷酸激酶 Ppk1 和肌醇六磷酸激酶 I6kA。多聚磷酸盐会改变去污剂不溶性粗细胞骨架中的蛋白质含量，但不会显著影响随机细胞运动性、细胞速度或 F-肌动蛋白水平。综上所述，这些数据表明，黏菌细胞可能利用多聚磷酸盐作为信号来感知其局部细胞密度，并降低细胞膜流动性和质膜循环利用，这也许是一种在细胞即将饥饿时保留摄入食物的机制。本文附有该论文第一作者的相关第一人称采访。
