Interplay between calcium and endoplasmic reticulum stress.

Cellular homeostasis is crucial for the healthy functioning of the organism. Disruption of cellular homeostasis activates endoplasmic reticulum (ER) stress coping responses including the unfolded protein response (UPR). There are three ER resident stress sensors responsible for UPR activation - IRE1α, PERK and ATF6. Ca signaling plays an important role in stress responses including the UPR and the ER is the main Ca storage organelle and a source of Ca for cell signaling. The ER contains many proteins involved in Ca import/export/ storage, Ca movement between different cellular organelles and ER Ca stores refilling. Here we focus on selected aspects of ER Ca homeostasis and its role in activation of the ER stress coping responses.