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

Calcium ions (Ca²⁺) play pivotal roles in regulating numerous cellular functions, including metabolism and growth, in normal and cancerous cells. Consequently, Ca²⁺ 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 Ca²⁺ signaling remains underexplored. In this study, we aimed to elucidate the mechanisms of Ca²⁺ regulation through the mitochondria, which are crucial to Ca²⁺ homeostasis. We investigated how Ca²⁺ 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 Ca²⁺ through Voltage-Dependent Anion Channel 1 (VDAC1), facilitated by intracellular tubulin, is influenced by ECM stiffness. Unraveling these Ca²⁺ regulatory mechanisms under various conditions offers a novel perspective for advancing biomedical studies involving Ca²⁺ signaling.