PDF(Pubmed)
Abstract：
Lysosomes are central players in cellular catabolism, signaling, and metabolic regulation. Cellular and environmental stresses that damage lysosomal membranes can compromise their function and release toxic content into the cytoplasm. Here, we examine how cells respond to osmotic stress within lysosomes. Using sensitive assays of lysosomal leakage and rupture, we examine acute effects of the osmotic disruptant glycyl-L-phenylalanine 2-naphthylamide (GPN). Our findings reveal that low concentrations of GPN rupture a small fraction of lysosomes, but surprisingly trigger Ca2+ release from nearly all. Chelating cytoplasmic Ca2+ makes lysosomes more sensitive to GPN-induced rupture, suggesting a role for Ca2+ in lysosomal membrane resilience. GPN-elicited Ca2+ release causes the Ca2+-sensor Apoptosis Linked Gene-2 (ALG-2), along with Endosomal Sorting Complex Required for Transport (ESCRT) proteins it interacts with, to redistribute onto lysosomes. Functionally, ALG-2, but not its ESCRT binding-disabled ΔGF122 splice variant, increases lysosomal resilience to osmotic stress. Importantly, elevating juxta-lysosomal Ca2+ without membrane damage by activating TRPML1 also recruits ALG-2 and ESCRTs, protecting lysosomes from subsequent osmotic rupture. These findings reveal that Ca2+, through ALG-2, helps bring ESCRTs to lysosomes to enhance their resilience and maintain organelle integrity in the face of osmotic stress.
摘要：
溶酶体是细胞分解代谢的核心参与者，信令,和代谢调节。损害溶酶体膜的细胞和环境压力可能损害其功能并将毒性内容物释放到细胞质中。这里,我们研究了细胞对溶酶体内渗透应激的反应。使用溶酶体渗漏和破裂的灵敏测定法，我们研究了渗透破坏剂甘氨酰-L-苯丙氨酸2-萘甲酰胺（GPN）的急性作用。我们的发现表明，低浓度的GPN会破坏一小部分溶酶体，但令人惊讶的是触发了几乎所有的Ca2+释放。螯合细胞质Ca2+使溶酶体对GPN诱导的破裂更敏感，提示Ca2+在溶酶体膜弹性中的作用。GPN引起的Ca2+释放引起Ca2+传感器凋亡连锁基因-2(ALG-2),以及与之相互作用的内体分选复合物（ESCRT）蛋白质，重新分配到溶酶体上.功能上,ALG-2，但不是其ESCRT结合禁用的ΔGF122剪接变体，增加溶酶体对渗透胁迫的复原力。重要的是,通过激活TRPML1升高近膜溶酶体Ca2+而无膜损伤也募集ALG-2和ESCRT，保护溶酶体免受随后的渗透破裂。这些发现揭示了Ca2+,通过ALG-2，有助于将ESCRT带到溶酶体，以增强其弹性并在面对渗透压力时保持细胞器的完整性。
