The GRK2 Promoter Is Regulated by Early-Growth Response Transcription Factor EGR-1

Single cell transcription revealing key transcription factors in embryonic kidney development

The development of the kidney is a complex process involving the differentiation of renal progenitor cells into various specialized cell types, including renal tubular epithelial cells and podocytes. Understanding the molecular mechanisms that govern this differentiation process is crucial for unraveling the intricacies of kidney development. Recent advances in single-cell RNA sequencing technology have enabled researchers to explore the heterogeneity of renal progenitor cells at an unprecedented resolution, offering new insights into the distinct subpopulations and transcriptional landscapes within these cells. Our analysis revealed the presence of distinct subpopulations within renal progenitor cells. Furthermore, we identified key transcription factors that are crucial for the differentiation of these progenitors into renal tubular epithelial cells and podocytes. These findings provide new insights into the molecular mechanisms of kidney development, highlighting the role of specific transcription factors in the differentiation of renal progenitor cells. Although further research is needed to fully validate these findings and their therapeutic potential, this study provides a valuable foundation for future exploration of kidney regeneration strategies.

The roles of G protein-coupled receptor kinase 2 in renal diseases

G protein-coupled receptor (GPCR) kinase 2 (GRK2) is an integrative node in many signalling network cascades. An emerging study indicates that GRK2 can interact with GPCRs and non-GPCR substrates in both kinase-dependent and -independent modes. Alterations in the functional levels of GRK2 have been found in a variety of renal diseases, such as hypertension-related kidney injury, sepsis-associated acute kidney injury (S-AKI), cardiorenal syndrome (CRS), acute kidney injury (AKI), age-related kidney injury or hyperglycemia-related kidney injury. Abnormal GRK2 expression contribute to the development of renal diseases, making them promising molecular targets for treating renal diseases. Blocking the prostaglandin E2 (PGE2)-EP1-Gaq-Ca2+ signal pathway in glomerular mesangial cells (GMCs) by internalizing prostaglandin E2 receptor 1 (EP1) with GRK2 may be a potential treatment for diabetic nephropathy (DN). In addition, GRK2 inhibition may have therapeutic effects in a variety of renal diseases, such as SLE-related kidney injury, DN, age-related kidney injury, hypertension-related kidney injury, and CRS. However, there is still a long way to go for the large-scale application of GRK2 inhibition in the field of renal diseases. In this review, we discuss recent updates in understanding the role of GRK2 in kidney dysfunction. Furthermore, we explore the potential of GRK2 as a possible therapeutic target for renal pathologies. We believe it will shed light on the future development of small-molecule inhibitors of GRK, as well as the clinical applications in renal diseases.

Characterization of the G protein-coupled receptor kinase 6 promoter reveals a functional CREB binding site

Background

G protein-coupled receptor kinase 6 (GRK6) is part of the G protein-coupled receptor kinase family, whose members act as key regulators of seven-transmembrane receptor signalling. GRK6 seems to play a role in regulation of inflammatory processes, but mechanisms of transcriptional regulation of GRK6 expression in inflammatory cell lines have not been characterized. Protein kinase C (PKC) signalling is also involved in inflammatory regulation and an impact of PKC activation on GRK6 protein expression was described previously. Thus, the aim of this study was to 1) characterize the GRK6 promoter, and 2) investigate a potential influence of PKC on GRK6 expression.

Methods

Five deletion constructs of the GRK6 promoter were cloned. After transient transfection into a human T cell line, promoter activity was assessed using luciferase reporter gene assays. Putative transcription factor binding sites were identified, mutated, and binding was investigated using electrophoretic mobility shift assays (EMSA). Following stimulation with a PKC activator, GRK6 expression on mRNA and protein levels was assessed by reverse transcriptase qPCR and Western blots.

Results

Investigation of the GRK6 promoter revealed a putative cAMP responsive element (CRE), whose mutation led to decreased promoter activity (p = 0.0006). Functionality of the CRE binding protein (CREB) binding site was verified in EMSA blots. Stimulation with a PKC activator resulted in decreased GRK6 promoter activity (p = 0.0027), mRNA (p = 0.04) and protein expression.

Conclusion

We characterized the human GRK6 promoter and identified promoter activity to be influenced by a CREB binding site. PKC might be one determinant contributing to altered GRK6 expression.

SNPs in Sites for DNA Methylation, Transcription Factor Binding, and miRNA Targets Leading to Allele-Specific Gene Expression and Contributing to Complex Disease Risk: A Systematic Review

INTRODUCTION

The complex genetic diversity among human populations results from an assortment of factors acting at various sequential levels, including mutations, population migrations, genetic drift, and selection. Although there are a plethora of DNA sequence variations identified through genome-wide association studies (GWAS), the challenge remains to explain the mechanisms underlying interindividual phenotypic disparity accounting for disease susceptibility. Single nucleotide polymorphisms (SNPs) present in the sites for DNA methylation, transcription factor (TF) binding, or miRNA targets can alter the gene expression. The systematic review aimed to evaluate the complex crosstalk among SNPs, miRNAs, DNA methylation, and TFs for complex multifactorial disease risk.

METHODS

PubMed and Scopus databases were used from inception until May 15, 2019. Initially, screening of articles involved studies assessing the interaction of SNPs with TFs, DNA methylation, or miRNAs resulting in allele-specific gene expression in complex multifactorial diseases. We also included the studies which provided experimental validation of the interaction of SNPs with each of these factors. The results from various studies on multifactorial diseases were assessed.

RESULTS

A total of 11 articles for SNPs interacting with DNA methylation, 30 articles for SNPs interacting with TFs, and 11 articles for SNPs in miRNA binding sites were selected. The interactions of SNPs with epigenetic factors were found to be implicated in different types of cancers, autoimmune diseases, cardiovascular diseases, diabetes, and asthma.

CONCLUSION

The systematic review provides evidence for the interplay between genetic and epigenetic risk factors through allele-specific gene expression in various complex multifactorial diseases.

G protein-coupled receptor kinase 2 (GRK2) as a multifunctional signaling hub

Accumulating evidence indicates that G protein-coupled receptor kinase 2 (GRK2) is a versatile protein that acts as a signaling hub by modulating G protein-coupled receptor (GPCR) signaling and also via phosphorylation or scaffolding interactions with an extensive number of non-GPCR cellular partners. GRK2 multifunctionality arises from its multidomain structure and from complex mechanisms of regulation of its expression levels, activity, and localization within the cell, what allows the precise spatio-temporal shaping of GRK2 targets. A better understanding of the GRK2 interactome and its modulation mechanisms is helping to identify the GRK2-interacting proteins and its substrates involved in the participation of this kinase in different cellular processes and pathophysiological contexts.

High-glucose induces cardiac myocytes apoptosis through Foxo1 /GRK2 signaling pathway

High glucose-induced cardiac myocytes apoptosis has been well demonstrated, but the mechanism remains unknown. In this study, we found that exposure of cardiac H9c2 cells to high glucose promoted Foxo1 and GRK2 expression, and induced autophagy. Further investigation showed that high glucose simultaneously increased the expression of cytoplasmic and nuclear Foxo1. Inhibition of Foxo1 reduced GRK2 expression and blocked autophagy, enhancing high glucose-induced apoptosis. GRK2 knockdown did not significantly affect Foxo1 expression and autophagy, but attenuated high glucose-induced apoptosis. Intriguingly, GRK2 knockdown reduced ROS generation. NAC treatment not only reduced the levels of cytoplasmic and nuclear Foxo1, but also inhibited GRK2 expression and autophagy, remarkably reducing high glucose-induced apoptosis. Inhibition of autophagy did not notably affect the expression of Foxo1 and GRK2, but enlarged high glucose-induced apoptosis. ChIP assay and Luciferase reporter assay confirmed that Foxo1 positively regulated GRK2 transcription. These results suggested that Foxo1 was involved in glucose-induced apoptosis by regulating GRK2 expression and autophagy.

GRK2 and GRK5 as therapeutic targets and their role in maladaptive and pathological cardiac hypertrophy

INTRODUCTION

One in every four deaths in the United States is attributed to cardiovascular disease, hence the development and employment of novel and effective therapeutics are necessary to improve the quality of life and survival of affected patient. Pathological hypertrophy is a maladaptive response by the heart to relieve wall stress that could result from cardiovascular disease. Maladaptive hypertrophy can lead to further disease progression and complications such as heart failure; hence, efforts to target hypertrophy to prevent and treat further morbidity and mortality are necessary. Areas covered: This review summarizes the compelling literature that describes the mechanistic role of GRK2 and GRK5 in maladaptive cardiac hypertrophy; it examines the approaches to inhibit these kinases in hypertrophic animal models and furthermore, it assesses the potential of GRK2 and GRK5 as therapeutic targets for hypertrophy. Expert opinion: GRK2 and GRK5 are novel therapeutic targets for pathological hypertrophy and may have added benefits of ameliorating morbidity and mortality. Despite the lesser researched role of GRK2 in cardiac hypertrophy, it may be the advantageous strategy for treating cardiac hypertrophy because of its role in other maladaptive pathways. Anti-GRK2 therapy optimization and the discovery and development of specific GRK2 and GRK5 small-molecule inhibitors is necessary for the eventual application of successful, effective therapeutics.