Expression of Human DNAJ (Heat Shock Protein-40) B3 in Humanized UDP-glucuronosyltransferase 1 Mice

DNAJB3 attenuates ER stress through direct interaction with AKT

Metabolic stress involved in several dysregulation disorders such as type 2 diabetes mellitus (T2DM) results in down regulation of several heat shock proteins (HSPs) including DNAJB3. This down regulation of HSPs is associated with insulin resistance (IR) and interventions which induce the heat shock response (HSR) help to increase the insulin sensitivity. Metabolic stress leads to changes in signaling pathways through increased activation of both c-jun N-terminal kinase-1 (JNK1) and the inhibitor of κB inflammatory kinase (IKKβ) which in turn leads to inactivation of insulin receptor substrates 1 and 2 (IRS-1 and IRS-2). DNAJB3 interacts with both JNK1 and IKKβ kinases to mitigate metabolic stress. In addition DNAJB3 also activates the PI3K-PKB/AKT pathway through increased phosphorylation of AKT1 and its substrate AS160, a Rab GTPase-activating protein, which results in mobilization of GLUT4 transporter protein and improved glucose uptake. We show through pull down that AK T1 is an interacting partner of DNAJB3, further confirmed by isothermal titration calorimetry (ITC) which quantified the avidity of AKT1 for DNAJB3. The binding interface was identified by combining protein modelling with docking of the AKT1-DNAJB3 complex. DNAJB3 is localized in the cytoplasm and ER, where it interacts directly with AKT1 and mobilizes AS160 for glucose transport. Inhibition of AKT1 resulted in loss of GLUT4 translocation activity mediated by DNAJB3 and also abolished the protective effect of DNAJB3 on tunicamycin-induced ER stress. Taken together, our findings provide evidence for a direct protein-protein interaction between DNAJB3 and AKT1 upon which DNAJB3 alleviates ER stress and promotes GLUT4 translocation.

Transcriptional Regulation of Structural and Functional Adaptations in a Developing Adulthood Myocardium

The development of the heart follows a synergic action of several signaling pathways during gestational, pre- & postnatal stages. The current study aimed to investigate whether the myocardium experiences transcriptional changes during the transition from post-natal to adult hood stages. Herein, we used C57/B16/J mice at 4 (28- days; post-natal/PN) and 20 weeks (adulthood/AH) of ages and employed the next generation RNAseq (NGS) to profile the transcriptome and echocardiography analysis to monitor the structural/functional changes in the heart. NGS-based RNA-seq revealed that 1215 genes were significantly upregulated and 2549 were down regulated in the AH versus PN hearts, indicating a significant transcriptional change during this transition.

A synchronized cardiac transcriptional regulation through cell cycle, growth hormones, redox homeostasis and metabolic pathways was noticed in both PN and AH hearts. Echocardiography reveals significant structural and functional (i.e. systolic/diastolic) changes during the transition of PN to adult stage. Particularly, a progressive decline in ejection fraction and cardiac output was observed in AH hearts. These structural adaptations are in line with critical signaling pathways that drive the maturation of heart during AH. Overall, we have presented a comprehensive transcriptomic analysis along with structural-functional relationship during the myocardial development in adult mice.

Role of the DNAJ/HSP40 family in the pathogenesis of insulin resistance and type 2 diabetes

Insulin resistance (IR) underpins a wide range of metabolic disorders including type 2 diabetes (T2D), metabolic syndrome and cardiovascular diseases. IR is characterized by a marked reduction in the magnitude and/or delayed onset of insulin to stimulate glucose disposal. This condition is due to defects in one or several intracellular intermediates of the insulin signaling cascade, ranging from insulin receptor substrate (IRS) inactivation to reduced glucose phosphorylation and oxidation. Genetic predisposition, as well as other precipitating factors such as aging, obesity, and sedentary lifestyles are among the risk factors underlying the pathogenesis of IR and its subsequent progression to T2D. One of the cardinal hallmarks of T2D is the impairment of the heat shock response (HSR). Human and animal studies provided compelling evidence of reduced expression of several components of the HSR (i.e. Heat shock proteins or HSPs) in diabetic samples in a manner that correlates with the degree of IR. Interventions that induce the HSR, irrespective of the means to achieve it, proved their effectiveness in enhancing insulin sensitivity and improving glycemic index. However, most of these studies have been focused on HSP70 family. In this review, we will focus on the novel role of DNAJ/HSP40 cochaperone family in metabolic diseases associated with IR.

Identification of a New QTL Region on Mouse Chromosome 1 Responsible for Male Hypofertility: Phenotype Characterization and Candidate Genes

Male fertility disorders often have their origin in disturbed spermatogenesis, which can be induced by genetic factors. In this study, we used interspecific recombinant congenic mouse strains (IRCS) to identify genes responsible for male infertility. Using ultrasonography, in vivo and in vitro fertilization (IVF) and electron microscopy, the phenotyping of several IRCS carrying mouse chromosome 1 segments of Mus spretus origin revealed a decrease in the ability of sperm to fertilize. This teratozoospermia included the abnormal anchoring of the acrosome to the nucleus and a persistence of residual bodies at the level of epididymal sperm midpiece. We identified a quantitative trait locus (QTL) responsible for these phenotypes and we have proposed a short list of candidate genes specifically expressed in spermatids. The future functional validation of candidate genes should allow the identification of new genes and mechanisms involved in male infertility.

MicroRNA-877-5p is involved in the trovafloxacin-induced liver injury

Trovafloxacin develops severe hepatotoxicity; however, the underlying mechanism of the trovafloxacin-induced liver injury has not been cleared. It has been shown that microRNAs (miRNAs) can be involved in the development of drug-induced liver injuries. We performed a miRNA microarray analysis to identify hepatic miRNAs that were induced or reduced by trovafloxacin in mice. It was demonstrated that miR-877-5p was the most increased miRNA in the mouse liver 24h after the trovafloxacin administration. To investigate the role of miR-877-5p in the liver, we established miR-877-5p-overexpressed HepG2 cells. Microarray analysis detected altered expressions in 2077 (>2-fold) and 1547 (<0.5-fold) genes in the miR-877-5p overexpressing cells compared to the mock cells. Especially, SLCO4C1, PEPCK, MT1M, HIST1H2BM, LGI1, and PLA2G2A were markedly increased or decreased in the miR-877-5p overexpressing cells. We conducted a correlation analysis between the expression levels of miR-877-5p and the six genes in eight miR-877-5p stably-expressed clones. It was shown that the PEPCK expression levels were correlated with miR-877-5p expression levels. PEPCK is associated with development of apoptotic cell death; therefore, the increased miR- 877-5p-induced PEPCK can be a trigger that is involved in the development of trovafloxacin-induced liver injury.