fig2

Figure 2. Regulation of apoptosis by miRNAs. All of miR-16, miR-15b, and miR-21 act on several molecular pathways, including Bak, Bcl-2, and Bax pathways during this process. miR-15b, miR-16, and Let-7 down regulate the expression of Bcl-2 (an anti-apoptotic protein) and trigger the release of cytochrome c (a pro-apoptotic factor). Down regulation of Bcl-2 reduces the mitochondrial membrane potential while cytosolic cytochrome c activates the caspase cascade, which subsequently leads to apoptosis. The role of miR-21 is two-fold: protection of neural cells and inhibition of apoptosis. Also, miR-21 down regulates PDCD4 to limit the activation of pro-apoptotic molecular pathways involving Bak and Bax. This, in turn, hinders apoptosis. Also, pro-apoptotic PTEN is down regulated by miR-21, resulting in an anti-apoptotic effect