Final answer:
Proapoptotic proteins play a key role in inhibiting the BH3-only proteins Bax and Bak in the intrinsic pathway of apoptosis. This regulation is essential for the mitochondrial release of cytochrome c and the subsequent activation of caspases necessary for programmed cell death.
Step-by-step explanation:
In the intrinsic pathway to apoptosis, a specific type of proteins known as proapoptotic proteins inhibit the BH3-only proteins (Bax and Bak). These proteins are crucial for the regulation of apoptosis, as they can promote the release of cytochrome c from the mitochondria, leading to the activation of caspases which are proteolytic enzymes that play a significant role in the execution phase of cell apoptosis. The BH123 proteins that include Bax and Bak are part of the Bcl-2 family, and their activity is regulated by various members of this family, including both pro and anti-apoptotic proteins.
One example of a regulatory mechanism is the suppression of Bax-induced apoptosis in yeast by the Vesicle-associated membrane protein (VAMP) of Arabidopsis, which acts downstream of the oxidative burst. In the context of therapeutic applications, Protein kinase N3 siRNA and BikDD plasmid DNA are examples of molecules that have been studied for their potential to influence apoptotic pathways and consequent therapeutic effects for diseases such as cancer.