Question

Imagine that you could microinject cytochrome c into the cytosol of both wild-type cells and cells that were lacking both Bax and Bak, which are apoptosis-promoting members of the Bcl2 family of proteins. Would you expect one, both, or neither of the cell lines to undergo apoptosis? Explain your reasoning.

Answer 1

Neither of the cell lines would undergo apoptosis

the cells will undergo apoptosis only if they have all the three BCl₃ family proteins. If bax and bak is absent means they can not form a channel to take out the cytochrome c. In such cells they can't follow the apoptosis.

Step-by-step explanation:

Apoptosis will happen to the nutrient-deficient cells, cells that lost contact with the neighboring cells, etc. Cytochrome C can act as an apoptosis signal. Usually, cytochrome c will come out from the mitochondria. This is recognized by BCl₂ family proteins. This includes 3 subfamilies.

1) pro-apoptotic proteins (eg. bax, bak, bok)

2) anti-apoptotic proteins (eg. Bcl2, Bcl-XL, Bcl-W, etc)

3) BH₃ family proteins (eg. bad, bid, bim, etc).

The anti-apoptotic protein inhibit the apoptosis. When the cell reaches up to death, the BH₃ family proteins will inhibit the action of anti-apoptotic proteins. This will activate the pro-apoptotic proteins. Initially, the pro-apoptotic protein will stay in the mitochondrial membrane as monomers. When the cell needs death or apoptosis, these monomers will get organized and form a channel. These channels help to take apoptotic signals like cytochrome c to outside. And this leads to apoptosis.