The endoplasmic reticulum-the caring mother of the cell.

In eukaryotic cells, various cellular functions are compartmentalized and performed by sophisticated and specialized organelles. However, the membrane-bounded organelles need to communicate with each other and with the cytoplasm, and sense the outside through the plasma membrane to coordinate various functions and to maintain cellular homeostasis. To maintain homeostasis, the information on the cellular state must be collected and appropriate responses initiated. The endoplasmic reticulum fulfils these functions. In this review, I will discuss various aspects of how the ER senses and relays information and acts to protect the cell, in what sometimes could be interpreted as an altruistic behavior.