MicroRNA‐502‐3p regulates the GABAergic synapse function in Alzheimer’s disease

Abstract

AbstractBackgroundAlzheimer’s disease (AD) is most common dementia in the aged individuals. Synapse dysfunction is the early event in the brain that initiate AD progression. Studies found the reduced inhibitory GABAergic synapse function in AD subjects.MethodsGlobal microRNA (miRNA) affymetrix analysis was performed on synaptosomal fractions from AD subjects and cognitively normal individuals. In silico analysis and luciferase assays were performed to confirm the miR‐502‐3p binding at the GABRA1 mRNA. MiR‐502‐3p agomiRs (overexpression) and antagomiRs (suppression) studies were performed on mouse primary hippocampal (HT22) neurons. The GABA receptor functions were accessed by electrophysiology studies using patch clamp analysis.ResultsOur global microRNA (miRNA) affymetrix study of synaptosomal fraction identified miR‐501‐3p/miR‐502‐3p as potential miRNAs. Data analysis showed the higher expression of miR‐502‐3p in the AD synapse relative to cognitively healthy synapse. On the other hand, Gamma‐Aminobutyric Acid Type A Receptor Subunit Alpha1 (GABRA1) levels were found to be reduced in AD synapse. In silico analysis and luciferase assay confirmed that miR‐502‐3p binds to multiple sites at the GABRA1 mRNA and suppresses its translation. In vitro studies using mouse primary hippocampal (HT22) neurons unveiled that miR‐502‐3p agomiRs (overexpression) decreased HT22 cell survival and antagomiRs (suppression) treated cells showed improved cell survival. qRT‐PCR, immunoblotting and immunostaining analysis conformed the reduced levels of GABRA1 by miR‐502‐3p overexpression, while suppression of miR‐502‐3p increases the GABRA1 protein levels. Further, electrophysiology studies using patch clamp analysis showed reduced GABA receptor functions and impaired chloride ion (Cl−) channel by over expression of miR‐502‐3p. On the other hand, reduced expression of miR‐502‐3p showed increased GABA receptor functions and Cl− influx into the cells.ConclusionOur initial observations confirmed that miR‐502‐3p modulate GABRA1 receptor functions. Therefore, miR‐502‐3p could be a therapeutic target to improve the GABAergic synapse function in AD.