Autophagy unleashes noncanonical microRNA functions

Area of Science:

• Molecular Biology
• Cell Biology
• Genetics

Background:

• MicroRNAs (miRNAs) are key post-transcriptional gene regulators.
• Their function in non-canonical, low-molecular weight complexes is poorly understood.
• miRNAs are involved in RNA-induced silencing complex (RISC)-mediated gene repression.

Purpose of the Study:

• To investigate the function of miRNAs in low-molecular weight complexes.
• To elucidate the role of microRNA-126 (MIR126) in endothelial cell survival under stress.
• To uncover novel mechanisms of miRNA-mediated apoptosis regulation.

Main Methods:

• Analysis of miRNA trafficking and complex formation in endothelial cells.
• Investigating the interaction of MIR126-5p with MEX3A and AGO2.
• Studying the nuclear localization and function of MIR126-5p.
• Assessing the impact of pathway disruption on apoptosis and atherosclerosis in vivo.

Main Results:

• High-shear stress and MTORC inhibition induce autophagy, affecting MIR126 strand trafficking.
• MIR126-5p forms a complex with MEX3A and AGO2 on autophagosomes, facilitating nuclear entry.
• Nuclear MIR126-5p directly inhibits caspase-3 (CASP3) activity by preventing its dimerization and activation.
• Disruption of the MIR126-5p/MEX3A/AGO2 pathway or autophagy exacerbates endothelial apoptosis and atherosclerosis progression.

Conclusions:

• MIR126-5p acts as a non-canonical inhibitor of caspase-3, directly modulating protein function.
• This pathway represents a novel mechanism linking autophagy and apoptosis in endothelial cells.
• The MIR126-5p-mediated inhibition of CASP3 is essential for endothelial cell survival and protection against atherosclerosis.