Endoplasmic reticulum & mitochondrial calcium homeostasis: The interplay with viruses.

Calcium ions (Ca) act as secondary messengers in a plethora of cellular processes and play crucial role in cellular organelle function and homeostasis. The average resting concentration of Ca is nearly 100 nM and in certain cells it can reach up to 1 µM. The high range of Ca concentration across the plasma membrane and intracellular Ca stores demands a well-coordinated maintenance of free Ca via influx, efflux, buffering and storage. Endoplasmic Reticulum (ER) and Mitochondria depend on Ca for their function and also serve as major players in intracellular Ca homeostasis. The ER-mitochondria interplay helps in orchestrating cellular calcium homeostasis to avoid any detrimental effect resulting from Ca overload or depletion. Since Ca plays a central role in many biological processes it is an essential component of the virus-host interactions. The large gradient across membranes enable the viruses to easily modulate this buffered environment to meet their needs. Viruses exploit Ca signaling to establish productive infection and evade the host immune defense. In this review we will detail the interplay between the viruses and cellular & ER-mitochondrial calcium signaling and the significance of these events on viral life cycle and disease pathogenesis.