Regulation of PDZ domain-containing 1 (PDZK1) expression by hepatocyte nuclear factor-1α (HNF1α) in human kidney

Susceptibility genes of hyperuricemia and gout

Gout is a chronic metabolic disease that seriously affects human health. It is also a major challenge facing the world, which has brought a heavy burden to patients and society. Hyperuricemia (HUA) is the most important risk factor for gout. In recent years, with the improvement of living standards and the change of dietary habits, the incidence of gout in the world has increased dramatically, and gradually tends to be younger. An increasing number of studies have shown that gene mutations may play an important role in the development of HUA and gout. Therefore, we reviewed the existing literature and summarized the susceptibility genes and research status of HUA and gout, in order to provide reference for the early diagnosis, individualized treatment and the development of new targeted drugs of HUA and gout.

Roles of circ_0000135/miR-140-3p/PDZK1 network in cervical cancer

PURPOSE

To explore the effect of circ_0000135/miR-140-3p/PDZ domain containing 1 (PDZK1) on the occurrence and development of cervical cancer.

METHODS

Clinical data were collected to verify circ_0000135/miR-140-3p/PDZK1 expression in cervical cancer. mRNA expressions of circ_0000135 and miR-140-3p were detected by real-time quantitative PCR. Correlation between circ_0000135 and miR-140-3p/miR-140-3p and PDZK1 was analyzed in vitro. Protein expression detection in cells was conducted by Western blot; while cell proliferation, invasion and cycle distribution by CCK8 assay, Transwell chamber assay and flow cytometry, respectively. Rescue and animal experiment were performed to verify the effect of circ_0000135/miR-140-3p/PDZK1 on cervical cancer.

RESULTS

circ_0000135 and PDZK1 expressions were increased, while those of miR-140-3p were decreased in cervical cancer tissues and cells (both P < 0.05). sh-circ_0000135 group had decreased cell viability, arrested cells in G0/G1 phase, decreased CyclinD1 expression, inhibited cell migration and invasion; sh-circ_0000135 group showed reduced tumor volume, weight, and lower Ki67 expression (all P < 0.05). circ_0000135 had conserved target of miR-140-3p. There was a direct interaction between circ_0000135 and miR-140-3p. miR-140-3p might have direct interaction with PDZK1. sh-circ_0000135 and/or miR-140-3p treatment showed obviously decreased PDZK1 expression, decreased cell activity, arrested cells in G0/G1 phase, downregulated cell migration and invasion; sh-circ_0000135 and/or miR-140-3p mimic treatment showed obviously decreased tumor volume, tumor weight, and Ki67 expression (all P < 0.05).

CONCLUSION

circ_0000135 may play an anti-tumor role on the progression of cervical cancer by sponging miR-140-3p to suppress the expression of PDZK1, providing a promising therapeutic target.

An evaluation method for uric acid uptake inhibition using primary human proximal tubule epithelial cells treated with insulin

The effects of uricosuric agents have been evaluated in vitro with indices of uric acid uptake into human urate transporter 1 (URAT1)-overexpressed oocytes or cells. In the present study, we evaluated a method using primary human renal proximal tubule epithelial cells (RPTECs). Pretreatment of RPTECs with insulin significantly increased the uptake of uric acid into these cells. The uric acid uptake was inhibited in a concentration-dependent manner by the URAT1 inhibitors benzbromarone and dotinurad. Therefore, effects of uricosuric agents can be evaluated by the novel method, which is closer to the physiological system compared with previous methods.

Urate transport in health and disease

Circulation of urate levels is determined by the balance between urate production and excretion, homeostasis regulated by the function of urate transporters in key epithelial tissues and cell types. Our understanding of these physiological processes and identification of the genes encoding the urate transporters has advanced significantly, leading to a greater ability to predict risk for urate-associated diseases and identify new therapeutics that directly target urate transport. Here, we review the identified urate transporters and their organization and function in the renal tubule, the intestinal enterocytes, and other important cell types to provide a fuller understanding of the complicated process of urate homeostasis and its role in human diseases. Furthermore, we review the genetic tools that provide an unbiased catalyst for transporter identification as well as discuss the role of transporters in determining the observed significant gender differences in urate-associated disease risk.

Function of Uric Acid Transporters and Their Inhibitors in Hyperuricaemia

Disorders of uric acid metabolism may be associated with pathological processes in many diseases, including diabetes mellitus, cardiovascular disease, and kidney disease. These diseases can further promote uric acid accumulation in the body, leading to a vicious cycle. Preliminary studies have proven many mechanisms such as oxidative stress, lipid metabolism disorders, and rennin angiotensin axis involving in the progression of hyperuricaemia-related diseases. However, there is still lack of effective clinical treatment for hyperuricaemia. According to previous research results, NPT1, NPT4, OAT1, OAT2, OAT3, OAT4, URAT1, GLUT9, ABCG2, PDZK1, these urate transports are closely related to serum uric acid level. Targeting at urate transporters and urate-lowering drugs can enhance our understanding of hyperuricaemia and hyperuricaemia-related diseases. This review may put forward essential references or cross references to be contributed to further elucidate traditional and novel urate-lowering drugs benefits as well as provides theoretical support for the scientific research on hyperuricemia and related diseases.

Interleukin-37 contributes to the pathogenesis of gout by affecting PDZ domain-containing 1 protein through the nuclear factor-kappa B pathway

OBJECTIVE

Our objective was to explore the molecular pathogenesis of the onset of gout and the mechanism underlying the effect of interleukin (IL)-37 on PDZ domain-containing 1 (PDZK1) protein through the nuclear factor-κB signaling pathway.

METHODS

Real-time PCR and western blotting were used to detect expression of PDZK1 mRNA and protein, respectively, in the HK-2 cell line. The inhibitors pyrrolidine dithiocarbamate (PDTC) and wortmannin were added to HK-2 cells stimulated by IL-37, and changes in PDZK1 protein were detected by western blotting.

RESULTS

Based on our previous research, we used 10 µmol/L PDTC. We detected no significant change in PDZK1 at the mRNA level among the IL-37, PDTC+IL-37, and wortmannin+IL-37 groups. With increasing IL-37 concentration, the protein level of PDZK1 increased. After adding wortmannin, the protein level of PDZK1 increased with increasing concentration of IL-37, albeit not significantly, and the level of PDZK1 remained lower than that with IL-37 alone. After adding PDTC, the protein level of PDZK1 showed a trend to decrease with increasing concentrations of IL-37 up to 40 ng/mL. The immunofluorescence results supported the western blot results.

CONCLUSIONS

IL-37 can affect protein expression of PDZK1, but not at the translational level, in the pathogenesis of gout.

Molecular Pathophysiology of Uric Acid Homeostasis

Uric acid, the end product of purine metabolism, plays a key role in the pathogenesis of gout and other disease processes. The circulating serum uric acid concentration is governed by the relative balance of hepatic production, intestinal secretion, and renal tubular reabsorption and secretion. An elegant synergy between genome-wide association studies and transport physiology has led to the identification and characterization of the major transporters involved with urate reabsorption and secretion, in both kidney and intestine. This development, combined with continued analysis of population-level genetic data, has yielded an increasingly refined mechanistic understanding of uric acid homeostasis as well as greater understanding of the genetic and acquired influences on serum uric acid concentration. The continued delineation of novel and established regulatory pathways that regulate uric acid homeostasis promises to lead to a more complete understanding of uric acid-associated diseases and to identify new targets for treatment.

Sex Differences in Urate Handling

Hyperuricemia, or elevated serum urate, causes urate kidney stones and gout and also increases the incidence of many other conditions including renal disease, cardiovascular disease, and metabolic syndrome. As we gain mechanistic insight into how urate contributes to human disease, a clear sex difference has emerged in the physiological regulation of urate homeostasis. This review summarizes our current understanding of urate as a disease risk factor and how being of the female sex appears protective. Further, we review the mechanisms of renal handling of urate and the significant contributions from powerful genome-wide association studies of serum urate. We also explore the role of sex in the regulation of specific renal urate transporters and the power of new animal models of hyperuricemia to inform on the role of sex and hyperuricemia in disease pathogenesis. Finally, we advocate the use of sex differences in urate handling as a potent tool in gaining a further understanding of physiological regulation of urate homeostasis and for presenting new avenues for treating the constellation of urate related pathologies.

Long noncoding RNA PENG upregulates PDZK1 expression by sponging miR-15b to suppress clear cell renal cell carcinoma cell proliferation

PDZK1 downregulation was reported to independently predict poor prognosis of clear cell renal cell carcinoma (ccRCC) patients and induce ccRCC development and progression. However, the underlying mechanism of PDZK1 downregulation remains unknown. Competing endogenous RNA (ceRNA) networks are emerging as new players in gene regulation and are associated with cancer development. ceRNAs regulate other RNA transcripts by competing for shared miRNAs. To investigate the role and mechanism of ceRNAs in PDZK1 downregulation and the development of ccRCC, we searched databases for miRNAs and lncRNAs that regulate PDZK1 expression in ccRCC tissues and assessed their effects in ccRCC. We found that miR-15b was expressed at higher levels in ccRCC tissues, and its upregulation was clinically associated with lower PDZK1 level, larger tumor size and shorter survival time of ccRCC patients. Conversely, a novel lncRNA (lncPENG) was expressed at a lower level in ccRCC tissues, and its downregulation was associated with the same effects as upregulation of miR-15b. Downregulation of miR-15b and upregulation of lncPENG resulted in a significant increase in PDZK1 level and inhibition of proliferation in vitro and in vivo. Mechanistically, lncPENG directly bound to miR-15b and effectively functioned as a sponge for miR-15b to modulate the expression of PDZK1. Thus, lncPENG may function as a ceRNA to attenuate miR-15b-dependent PDZK1 downregulation and inhibit cell proliferation, suggesting that it may be clinically valuable as a therapeutic target and a prognostic biomarker of ccRCC.

Target genes, variants, tissues and transcriptional pathways influencing human serum urate levels

Elevated serum urate levels cause gout and correlate with cardiometabolic diseases via poorly understood mechanisms. We performed a trans-ancestry genome-wide association study of serum urate in 457,690 individuals, identifying 183 loci (147 previously unknown) that improve the prediction of gout in an independent cohort of 334,880 individuals. Serum urate showed significant genetic correlations with many cardiometabolic traits, with genetic causality analyses supporting a substantial role for pleiotropy. Enrichment analysis, fine-mapping of urate-associated loci and colocalization with gene expression in 47 tissues implicated the kidney and liver as the main target organs and prioritized potentially causal genes and variants, including the transcriptional master regulators in the liver and kidney, HNF1A and HNF4A. Experimental validation showed that HNF4A transactivated the promoter of ABCG2, encoding a major urate transporter, in kidney cells, and that HNF4A p.Thr139Ile is a functional variant. Transcriptional coregulation within and across organs may be a general mechanism underlying the observed pleiotropy between urate and cardiometabolic traits.

The nuclear receptors PXR and LXR are regulators of the scaffold protein PDZK1

PDZK1 (NHERF3) interacts with membrane proteins whereby modulating their spatial arrangement, membrane stability, and function. One of the membrane proteins shown to be stabilized by interaction with PDZK1 is the HDL-receptor SR-BI (SCARB1). Testing the influence of TO 901317, a known activator of liver X receptor alpha (LXRα, NR1H3) which is a central regulator of the lipid homeostasis, Grefhorst et al. reported in 2012 that administration of TO 901317 did not affect PDZK1 expression and reduced the amount of SR-BI protein in mouse liver. Considering that TO 901317 also activates the xenosensor pregnane X receptor (PXR, NR1I2), it was aim of this study to further investigate the influence of LXRα and PXR activation on transcription of PDZK1. First, we tested the transactivation of PDZK1 by LXRα or PXR in cell-based reporter gene assays comparing the effect of prototypical ligands to that of TO 901317. Ligand mediated activation of LXRα increased, while that of PXR lowered luciferase activity. Further, we located the most likely binding site for LXRα and PXR on the PDZK1 promoter between -85 bp and -54 bp. The transcriptional regulation by LXRα was further supported showing enhanced mRNA expression of PDZK1 in HepG2 cells treated with the selective LXRα-agonist GW3965, while treatment with TO 901317 reduced the protein amount of PDZK1. Taken together, we provide evidence that both LXRα and PXR are transcriptional regulators of PDZK1 supporting the previous notion that the scaffold protein is part of cholesterol homeostasis and drug metabolism.