Question

You have the equipment to microinject cytochrome c into the cytosol of cells (i.e., with a microscopically thin needle to inject this protein into the cells). You perform this microinjection into both 1) wild-type cells and 2) cells in which both Bax and Bak, which are the death-promoting members of the Bcl-2 family, are defective (ie, both Bax and Bak are either missing or functionally inactive). Would you expect one, both, or neither of the cell types (wild-type and/or Bax/Bak mutant) to undergo apoptosis? Briefly explain your reasoning, making sure to explain the molecular mechanisms by which cytochrome c can affect apoptosis.

Answer 1

Answer=Both Cell Types (Wild and Bax/Bak Mutant) will undergo apoptosis

Explanation-

Bax and Bak makes outer mitochondrial membrane porous (permeable) for Cytochrome C so help in releasing Cytochrome C in Cytosol so if Bax/Bak mutant in a cell and Cytochrome C is injected into this cell then there is no impact of Bax/Bak mutant because Cytochrome C already present in the cytosol in both types of cell(Wild and Mutant).

In caspase dependent intrinsic apoptotic pathway the Mitochondria plays an central role by releasing Cytochrome C in Cytosol.The basic role of cytochrome C is to trigger the activation of caspase-9.Cytochrome C triggers the interaction of the cytosolic adapter protein Apaf-1 with procaspase-9 in a complex called apoptosome.The incorporation of procaspase-9 in to apoptosome triggers the auto activation cleavage.Caspase 9 in turn cleaves procaspase-3 to generate caspase-3 which cleaves targets that cause apoptosis of the cell.