Inhibition of the processing of miR-25 by HIPK2-Phosphorylated-MeCP2 induces NOX4 in early diabetic nephropathy

Abstract

Phosphorylated methyl-CpG binding protein2 (p-MeCP2) suppresses the processing of several microRNAs (miRNAs). Homeo-domain interacting protein kinase2 (HIPK2) phosphorylates MeCP2, a known transcriptional repressor. However, it is not known if MeCP2 and HIPK2 are involved in processing of miRNAs implicated in diabetic nephropathy. p-MeCP2 and HIPK2 levels were significantly increased, but Seven in Absentia Homolog1 (SIAH1), which mediates proteasomal degradation of HIPK2, was decreased in the glomeruli of streptozotocin injected diabetic mice. Among several miRNAs, miR-25 and its precursor were significantly decreased in diabetic mice, whereas primary miR-25 levels were significantly increased. NADPH oxidase4 (NOX4), a target of miR-25, was significantly increased in diabetic mice. Protein levels of p-MeCP2, HIPK2, and NOX4 were increased in high glucose (HG)- or TGF-β-treated mouse glomerular mesangial cells (MMCs). miR-25 (primary, precursor, and mature) and mRNA levels of genes indicated in the in vivo study showed similar trends of regulation in MMCs treated with HG or TGF-β. The HG- or TGF-β-induced upregulation of p-MeCP2, NOX4 and primary miR-25, but downregulation of precursor and mature miR-25, were attenuated by Hipk2 siRNA. These results demonstrate a novel role for the SIAH1/HIPK2/MeCP2 axis in suppressing miR-25 processing and thereby upregulating NOX4 in early diabetic nephropathy.

The nutrient sensor OGT regulates Hipk stability and tumorigenic-like activities inDrosophila

“…Given the nutrient-sensing nature of O-GlcNAc, it is conceivable that HIPK2 O-GlcNAcylation might contribute to the nutrient sensitivity of HIPK2 abundance. Intriguingly, a study shows that HIPK2 protein levels increased in a mouse model of diabetes, and the authors attributed the effect to down-regulation of the E3 ubiquitin ligase Siah-1 (52). Hence, the nutritional regulation of HIPK2 might be achieved by multiple strategies like direct O-GlcNAcylation and impairment of proteasome system, or their cooperative effects.…”

Interactions Among Non-Coding RNAs in Diabetic Nephropathy

“…Another miRNA is the miR-25 that negatively regulates NADPH oxidase-4 (Nox4) expression (an enzyme that produces ROS), and its expression was reduced in the renal tissue of DN rats (Fu et al, 2010). Importantly, the miR-25 expression is also regulated by Homeodomain-interacting protein kinase-2 (Hipk2) (Oh et al, 2016), indicating a complex regulation of HIPK2-miR-25-NOX4 in the maintenance of ROS. Furthermore, NOX4 gene expression is also regulated by miR-423-5p, that were downregulated in kidney tissues of DN patients (Xu et al, 2018), further re-affirm the complex and tight regulation of NOX4 gene.…”

Noncoding RNAs as therapeutic targets in early stage diabetic kidney disease

“…HIPK2 is a key regulator of kidney fibrosis [ 115 ], significantly inhibits miR-25 processing (miR-25 reduction and NOX4 increase) through phosphorylation of MeCP2, and was detected in diabetic kidney and MMC treated with TGF-β1. Therefore, the connection from HIPK2 to MeCP2 through miRNA processing is a potential mechanism underlying early stage DKD [ 116 ]. Nox4 was also identified as a target of miR-146a, which was down-regulated in high-glucose-treated endothelial cells [ 117 ].…”

“…Approaches to upregulate functional miR-NAs are more challenging than inhibition because stable and active molecules are required, although in - vivo delivery methods including adeno-associated virus vectors [ 129 ] and bacteriophage MS2 virus-like particles have been tested for overexpressing miRNAs [ 155 ]. Targeting negative regulators of miRNAs, such as lin28 (inhibitor of let-7 processing) [ 72 – 75 ] or HIPK2 (inhibitor of miR-25 processing) [ 114 – 116 , 156 , 157 ] by siRNA, antisense inhibitors, or chemical inhibitors might be possible ( Fig. 1 ).…”