Mu Baicong, Rutkowski David M, Grenci Gianluca, Vavylonis Dimitrios, Zhang Dan
Temasek Life Sciences Laboratory, 1 Research Link, National University of Singapore, 117604, Singapore.
Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117543, Singapore.
bioRxiv. 2024 Oct 21:2024.10.20.619261. doi: 10.1101/2024.10.20.619261.
Robust coordination of surface and volume changes is critical for cell integrity. Few studies have elucidated the plasma membrane (PM) remodeling events during cell surface and volume alteration, especially regarding PM sensing and its subsequent rearrangements. Here, using fission yeast protoplasts, we reveal a Ca-dependent mechanism for membrane addition that ensures PM integrity and allows its expansion during acute hypoosmotic cell swelling. We show that MscS-like mechanosensitive channels activated by PM tension control extracellular Ca influx, which triggers direct lipid transfer at endoplasmic reticulum (ER)-PM contact sites by conserved extended-synaptotagmins and accelerates exocytosis, enabling PM expansion necessary for osmotic equilibrium. Defects in any of these key events result in rapid protoplast rupture upon severe hypotonic shock. Our numerical simulations of hypoosmotic expansion further propose a cellular strategy that combines instantaneous non-vesicular lipid transfer with bulk exocytic membrane delivery to maintain PM integrity for dramatic cell surface/volume adaptation.
细胞表面和体积变化的稳健协调对于细胞完整性至关重要。很少有研究阐明细胞表面和体积改变过程中的质膜（PM）重塑事件，特别是关于PM感知及其随后的重排。在这里，我们使用裂殖酵母原生质体，揭示了一种依赖钙离子的膜添加机制，该机制可确保PM完整性，并使其在急性低渗细胞肿胀期间得以扩张。我们表明，由PM张力激活的MscS样机械敏感通道控制细胞外钙离子内流，这通过保守的延伸突触结合蛋白在内质网（ER）-PM接触位点触发直接脂质转移，并加速胞吐作用，从而实现渗透平衡所需的PM扩张。这些关键事件中的任何一个出现缺陷都会导致在严重低渗休克时原生质体迅速破裂。我们对低渗扩张的数值模拟进一步提出了一种细胞策略，该策略将瞬时非囊泡脂质转移与大量胞吐膜递送相结合，以维持PM完整性，从而实现显著的细胞表面/体积适应。
