Which protein is known for inhibiting apoptosis in cells?

BCL2 is known for its role in inhibiting apoptosis, which is the programmed cell death that occurs in multicellular organisms. This protein is integral to the regulation of the apoptotic process and functions by preventing the release of cytochrome c from mitochondria, a key event that initiates apoptosis. By inhibiting the apoptotic pathway, BCL2 contributes to cell survival, and its overexpression is commonly associated with various types of cancer, as it allows cancer cells to evade the normal death signals they would typically respond to.

In contrast, the other proteins mentioned are involved in different cellular processes. While ERBB2 (also known as HER2) plays a role in cell signaling related to growth and division, p53 is a critical tumor suppressor that promotes apoptosis in response to DNA damage, and the Rb protein is involved in cell cycle regulation and also promotes apoptosis under certain conditions. However, none of these proteins primarily focus on inhibiting apoptosis in the way BCL2 does.