Gene expression profiling indicate role of ER stress in miR-23a∼27a∼24-2 cluster induced apoptosis in HEK293T cells

Previously, we had reported that overexpression of miR-23a similar to 27a similar to 24-2 cluster induces caspase-dependent and -independent apoptosis via JNK in human embryonic kidney (HEK293T) cells. Herein, we describe the molecular mechanism(s) responsible for miR-23a similar to 27a similar to 24-2 cluster induced apoptosis. Gene expression profiling was used to characterize the transcriptional response to miR-23a similar to 27a similar to 24-2 cluster overexpression in HE K293T cells. The microarray analysis gave 1,025 differentially expressed genes and analysis of the gene expression data with Ingenuity Pathway Analysis (IPA) software revealed p53 signaling, oxidative stress response and mitochondrial dysfunction among the top processes being affected. This data substantiates our previous study where we had reported increase of ROS and the release of proapoptotic factors such as cytochrome c (cyt c) and apoptosis-inducing factor (AIF) from the mitochondria. Additionally, components of ER stress-mediated apoptosis pathway i.e., C/EBP homologous protein (CHOP/DDIT3/GADD153) and TRIB3, an Akt inhibitor were found to be significantly enriched. Also, the enhanced expression of ATF3 and ATF4 was observed at RNA as well as protein level in miR-23a similar to 27a similar to 24-2 cluster overexpressed HE K293T cells. Induction of BIM appeared to be specific, because ER stress caused only a minor change in the expression of the related BH3-only proteins BID or PUMA. The fact that miR-23a similar to 27a similar to 24-2 cluster triggered endoplasmic reticulum stress (ER stress) was further established by the increase in cytosolic calcium levels after overexpression of this cluster in HE K293T cells. These findings were also supported by PANTHER analysis wherein biological process categories of apoptosis and stress response were enriched. Taken together, this work underlines the role of ER stress in miR-23a similar to 27a similar to 24-2 cluster mediated apoptosis in HE K293T cells. Since the detailed knowledge of this cluster induced apoptosis has now been elucidated, the in vivo study of this cluster would help evaluate the prospect of its use as a therapeutic in diseases known to occur because of deregulation of apoptosis.