ECM stiffness regulates calcium influx into mitochondria via tubulin and VDAC1 activity.

Calcium ions (Ca 2+ ) play pivotal roles in regulating numerous cellular functions, including metabolism and growth, in normal and cancerous cells. Consequently, Ca 2+ signaling is a vital determinant of cell fate and influences both cell survival and death. These intracellular signals are susceptible to modulation by various factors, including changes in the extracellular environment, which leads to mechanical alterations. However, the effect of extracellular matrix (ECM) stiffness variations on intracellular Ca 2+ signaling remains underexplored. In this study, we aimed to elucidate the mechanisms of Ca 2+ regulation through the mitochondria, which are crucial to Ca 2+ homeostasis. We investigated how Ca 2+ regulatory mechanisms adapt to different levels of ECM stiffness by simultaneously imaging the mitochondria and endoplasmic reticulum (ER) in live cells using genetically encoded biosensors. Our findings revealed that the uptake of mitochondrial Ca 2+ through Voltage-Dependent Anion Channel 1 (VDAC1), facilitated by intracellular tubulin, is influenced by ECM stiffness. Unraveling these Ca 2+ regulatory mechanisms under various conditions offers a novel perspective for advancing biomedical studies involving Ca 2+ signaling.