The physiological determinants of drug-induced lysosomal stress resistance

Many weakly basic, lipophilic drugs accumulate in lysosomes and exert complex, pleiotropic effects on organelle structure and function. Thus, modeling how perturbations of lysosomal physiology affect the maintenance of lysosomal ion homeostasis is necessary to elucidate the key factors which determine the toxicological effects of lysosomotropic agents, in a cell-type dependent manner. Accordingly, a physiologically-based mathematical modeling and simulation approach was used to explore the dynamic, multi-parameter phenomenon of lysosomal stress. With this approach, parameters that are either directly involved in lysosomal ion transportation or lysosomal morphology were transiently altered to investigate their downstream effects on lysosomal physiology reflected by the changes they induce in lysosomal pH, chloride, and membrane potential. In addition, combinations of parameters were simultaneously altered to assess which parameter was most critical for recovery of normal lysosomal physiology. Lastly, to explore the relationship between organelle morphology and induced stress, we investigated the effects of parameters controlling organelle geometry on the restoration of normal lysosomal physiology following a transient perturbation. Collectively, our results indicate a key, interdependent role of V-ATPase number and membrane proton permeability in lysosomal stress tolerance. This suggests that the cell-type dependent regulation of V-ATPase subunit expression and turnover, together with the proton permeability properties of the lysosomal membrane, is critical to understand the differential sensitivity or resistance of different cell types to the toxic effects of lysosomotropic drugs.诸多弱碱性亲脂性药物可在溶酶体（lysosomes）中蓄积，并对细胞器的结构与功能产生复杂的多效性影响。因此，构建溶酶体生理扰动如何影响溶酶体离子稳态维持的模型，对于阐明以细胞类型依赖性方式决定溶酶体靶向药物毒理学效应的关键因子而言至关重要。据此，本研究采用基于生理的数学建模与仿真方法，探究溶酶体应激这一动态多参数现象。借助该方法，研究人员对直接参与溶酶体离子转运或调控溶酶体形态的参数进行瞬时扰动，以探究其对溶酶体生理的下游效应——该效应可通过溶酶体pH值、氯离子浓度与膜电位的变化得以体现。此外，研究人员同时对多组参数进行联合扰动，以评估哪些参数对于溶酶体生理的正常恢复最为关键。最后，为探究细胞器形态与诱导应激之间的关联，本研究针对瞬时扰动后调控细胞器几何形状的参数对溶酶体生理正常恢复的影响展开了分析。综上，本研究结果表明，液泡型ATP酶（V-ATPase）的数量与膜质子通透性在溶酶体应激耐受性中发挥关键且相互依存的作用。这提示，调控V-ATPase亚基表达与周转的细胞类型依赖性机制，结合溶酶体膜的质子通透性特性，对于理解不同细胞类型对溶酶体靶向药物毒理学效应的差异性敏感性或抗性至关重要。