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Liu L, Deng Y, Cai Y, Lu P, Guo Y, Zhang C, Li Q, Zhang T, Han M, Xu G. Ablation of Gsa impairs renal tubule proliferation after injury via CDK2/cyclin E. Am J Physiol Renal Physiol 2020; 318:F793-F803. [PMID: 32036696 DOI: 10.1152/ajprenal.00367.2019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Acute kidney injury has a high global morbidity associated with an increased risk of death and chronic kidney disease. Renal tubular epithelial cell regeneration following injury may be a decisive factor in renal repair or the progression of acute kidney injury to chronic kidney disease, but the underlying mechanism of abnormal renal tubular repair remains unclear. In the present study, we investigated the role of heterotrimeric G stimulatory protein α-subunit (Gsa) in renal tubular epithelial cell regeneration. We generated renal tubule epithelium-specific Gsa knockout (GsaKspKO) mice to show the essential role of Gsa in renal tubular epithelial cell regeneration in two AKI models: acute aristolochic acid nephropathy (AAN) and unilateral ischemia-reperfusion injury (UIRI). GsaKspKO mice developed more severe renal impairment after AAN and UIRI, higher serum creatinine levels, and more substantial tubular necrosis than wild-type mice. More importantly, Gsa inactivation impaired renal tubular epithelial cell proliferation by reducing bromodeoxyuridine+ cell numbers in the AAN model and inhibiting cyclin-dependent kinase 2/cyclin E1 expression in the UIRI model. This reduced proliferation was further supported in vitro with Gsa-targeting siRNA. Downregulation of Gsa inhibited tubular epithelial cell proliferation in HK-2 and mIMCD-3 cells. Furthermore, Gsa downregulation inhibited cyclin-dependent kinase 2/cyclin E1 expression, which was dependent on the Raf-MEK-ERK signaling pathway. In conclusion, Gsa is required for tubular epithelial cell regeneration during kidney repair after AKI. Loss of Gsa impairs renal tubular epithelial cell regeneration by blocking the Raf-MEK-ERK pathway.
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Affiliation(s)
- Lele Liu
- Department of Nephrology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Yuanjun Deng
- Department of Nephrology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Yang Cai
- Department of Nephrology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Pingfan Lu
- Department of Nephrology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Yiyan Guo
- Department of Nephrology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Chunjiang Zhang
- Department of Nephrology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Qian Li
- Department of Nephrology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Tianjing Zhang
- Department of Nephrology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Min Han
- Department of Nephrology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Gang Xu
- Department of Nephrology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
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Zhang B, Tran U, Wessely O. Polycystin 1 loss of function is directly linked to an imbalance in G-protein signaling in the kidney. Development 2018. [PMID: 29530879 DOI: 10.1242/dev.158931] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The development of the kidney relies on the establishment and maintenance of a precise tubular diameter of its functional units, the nephrons. This process is disrupted in polycystic kidney disease (PKD), resulting in dilations of the nephron and renal cyst formation. In the course of exploring G-protein-coupled signaling in the Xenopus pronephric kidney, we discovered that loss of the G-protein α subunit, Gnas, results in a PKD phenotype. Polycystin 1, one of the genes mutated in human PKD, encodes a protein resembling a G-protein-coupled receptor. Furthermore, deletion of the G-protein-binding domain present in the intracellular C terminus of polycystin 1 impacts functionality. A comprehensive analysis of all the G-protein α subunits expressed in the Xenopus pronephric kidney demonstrates that polycystin 1 recruits a select subset of G-protein α subunits and that their knockdown - as in the case of Gnas - results in a PKD phenotype. Mechanistically, the phenotype is caused by increased endogenous G-protein β/γ signaling and can be reversed by pharmacological inhibitors as well as knocking down Gnb1. Together, our data support the hypothesis that G proteins are recruited to the intracellular domain of PKD1 and that this interaction is crucial for its function in the kidney.
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Affiliation(s)
- Bo Zhang
- Cleveland Clinic Foundation, Lerner Research Institute, Department of Cellular and Molecular Medicine, 9500 Euclid Avenue/NC10, Cleveland, OH 44195, USA.,LSU Health Sciences Center, Department of Cell Biology and Anatomy, 1901 Perdido Street, New Orleans, LA 70112, USA
| | - Uyen Tran
- Cleveland Clinic Foundation, Lerner Research Institute, Department of Cellular and Molecular Medicine, 9500 Euclid Avenue/NC10, Cleveland, OH 44195, USA
| | - Oliver Wessely
- Cleveland Clinic Foundation, Lerner Research Institute, Department of Cellular and Molecular Medicine, 9500 Euclid Avenue/NC10, Cleveland, OH 44195, USA
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Shi W, Xu G, Wang C, Sperber SM, Chen Y, Zhou Q, Deng Y, Zhao H. Heat shock 70-kDa protein 5 (Hspa5) is essential for pronephros formation by mediating retinoic acid signaling. J Biol Chem 2015; 290:577-89. [PMID: 25398881 PMCID: PMC4281759 DOI: 10.1074/jbc.m114.591628] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2014] [Revised: 11/09/2014] [Indexed: 12/17/2022] Open
Abstract
Heat shock 70-kDa protein 5 (Hspa5), also known as binding immunoglobulin protein (Bip) or glucose-regulated protein 78 (Grp78), belongs to the heat shock protein 70 kDa family. As a multifunctional protein, it participates in protein folding and calcium homeostasis and serves as an essential regulator of the endoplasmic reticulum (ER) stress response. It has also been implicated in signal transduction by acting as a receptor or co-receptor residing at the plasma membrane. Its function during embryonic development, however, remains largely elusive. In this study, we used morpholino antisense oligonucleotides (MOs) to knock down Hspa5 activity in Xenopus embryos. In Hspa5 morphants, pronephros formation was strongly inhibited with the reduction of pronephric marker genes Lim homeobox protein 1 (lhx1), pax2, and β1 subunit of Na/K-ATPase (atp1b1). Pronephros tissue was induced in vitro by treating animal caps with all-trans-retinoic acid and activin. Depletion of Hspa5 in animal caps, however, blocked the induction of pronephros as well as reduced the expression of retinoic acid (RA)-responsive genes, suggesting that knockdown of Hspa5 attenuated RA signaling. Knockdown of Hspa5 in animal caps resulted in decreased expression of lhx1, a transcription factor directly regulated by RA signaling and essential for pronephros specification. Co-injection of Hspa5MO with lhx1 mRNA partially rescued the phenotype induced by Hspa5MO. These results suggest that the RA-Lhx1 signaling cascade is involved in Hspa5MO-induced pronephros malformation. This study shows that Hspa5, a key regulator of the unfolded protein response, plays an essential role in pronephros formation, which is mediated in part through RA signaling during early embryonic development.
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Affiliation(s)
- Weili Shi
- From the Key Laboratory for Regenerative Medicine, Ministry of Education, School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong Special Administrative Region (SAR), China
| | - Gang Xu
- School of Chinese Medicine, Hong Kong Baptist University, 7 Baptist University Road, Kowloon Tong, Hong Kong SAR, China
| | - Chengdong Wang
- From the Key Laboratory for Regenerative Medicine, Ministry of Education, School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong Special Administrative Region (SAR), China, Shenzhen Research Institute, The Chinese University of Hong Kong, Shenzhen 518057, China
| | - Steven M Sperber
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, New York 10029-6574
| | - Yonglong Chen
- Key Laboratory of Regenerative Biology, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China, and
| | - Qin Zhou
- Division of Molecular Nephrology and Creative Training Center for Undergraduates, Ministry of Education Key Laboratory of Laboratory Medicine Diagnostics, College of Laboratory Medicine, Chongqing Medical University, Chongqing 400016, China
| | - Yi Deng
- Department of Biology, South University of Science and Technology of China, Shenzhen 518055, China,
| | - Hui Zhao
- From the Key Laboratory for Regenerative Medicine, Ministry of Education, School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong Special Administrative Region (SAR), China, Shenzhen Research Institute, The Chinese University of Hong Kong, Shenzhen 518057, China,
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Cerqueira DM, Tran U, Romaker D, Abreu JG, Wessely O. Sterol carrier protein 2 regulates proximal tubule size in the Xenopus pronephric kidney by modulating lipid rafts. Dev Biol 2014; 394:54-64. [PMID: 25127994 DOI: 10.1016/j.ydbio.2014.07.025] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2013] [Revised: 05/29/2014] [Accepted: 07/30/2014] [Indexed: 11/29/2022]
Abstract
The kidney is a homeostatic organ required for waste excretion and reabsorption of water, salts and other macromolecules. To this end, a complex series of developmental steps ensures the formation of a correctly patterned and properly proportioned organ. While previous studies have mainly focused on the individual signaling pathways, the formation of higher order receptor complexes in lipid rafts is an equally important aspect. These membrane platforms are characterized by differences in local lipid and protein compositions. Indeed, the cells in the Xenopus pronephric kidney were positive for the lipid raft markers ganglioside GM1 and Caveolin-1. To specifically interfere with lipid raft function in vivo, we focused on the Sterol Carrier Protein 2 (scp2), a multifunctional protein that is an important player in remodeling lipid raft composition. In Xenopus, scp2 mRNA was strongly expressed in differentiated epithelial structures of the pronephric kidney. Knockdown of scp2 did not interfere with the patterning of the kidney along its proximo-distal axis, but dramatically decreased the size of the kidney, in particular the proximal tubules. This phenotype was accompanied by a reduction of lipid rafts, but was independent of the peroxisomal or transcriptional activities of scp2. Finally, disrupting lipid micro-domains by inhibiting cholesterol synthesis using Mevinolin phenocopied the defects seen in scp2 morphants. Together these data underscore the importance for localized signaling platforms in the proper formation of the Xenopus kidney.
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Affiliation(s)
- Débora M Cerqueira
- Cleveland Clinic Foundation, Lerner Research Institute, Department Cellular and Molecular Medicine, 9500 Euclid Avenue/NC10 Cleveland, OH 44195, USA; Universidade Federal do Rio de Janeiro, Instituto de Ciências Biomédicas-CCS, Av. Carlos Chagas Filho, 373 bloco F2 sala 15, Rio de Janeiro 21949-590, Brazil
| | - Uyen Tran
- Cleveland Clinic Foundation, Lerner Research Institute, Department Cellular and Molecular Medicine, 9500 Euclid Avenue/NC10 Cleveland, OH 44195, USA
| | - Daniel Romaker
- Cleveland Clinic Foundation, Lerner Research Institute, Department Cellular and Molecular Medicine, 9500 Euclid Avenue/NC10 Cleveland, OH 44195, USA
| | - José G Abreu
- Universidade Federal do Rio de Janeiro, Instituto de Ciências Biomédicas-CCS, Av. Carlos Chagas Filho, 373 bloco F2 sala 15, Rio de Janeiro 21949-590, Brazil
| | - Oliver Wessely
- Cleveland Clinic Foundation, Lerner Research Institute, Department Cellular and Molecular Medicine, 9500 Euclid Avenue/NC10 Cleveland, OH 44195, USA.
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MicroRNAs are critical regulators of tuberous sclerosis complex and mTORC1 activity in the size control of the Xenopus kidney. Proc Natl Acad Sci U S A 2014; 111:6335-40. [PMID: 24733901 DOI: 10.1073/pnas.1320577111] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
MicroRNAs (miRNAs) are major posttranscriptional regulators of a wide variety of biological processes. However, redundancy among most miRNAs has made it difficult to identify their in vivo functions. We previously demonstrated that global inhibition of miRNA biogenesis in Xenopus resulted in a dramatically smaller pronephric kidney. This suggested that microRNAs play a pivotal role in organ size control. Here we now provide a detailed mechanistic explanation for this phenotype. We identified that the activation of the mechanistic target of rapamycin complex 1 (mTORC1) by Insulin and insulin-like growth factor (Igf) 2 is an important regulator in kidney growth, which in turn is modulated by microRNAs. Molecular analyses demonstrate that microRNAs set a threshold for mTORC1 signaling by down-regulating one of its core negative regulators, tuberous sclerosis 1 (Tsc1). Most importantly, this rheostat can be reprogrammed experimentally. Whereas knockdown of miRNAs causes growth arrest, concomitant knockdown of Tsc1 restores mTORC1 activity and proximal tubular size. Together, these data establish a previously unidentified in vivo paradigm for the importance of posttranscriptional regulation in organ size control.
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6
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The bigger the better: determining nephron size in kidney. Pediatr Nephrol 2014; 29:525-30. [PMID: 23974984 PMCID: PMC3944135 DOI: 10.1007/s00467-013-2581-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/04/2013] [Revised: 07/12/2013] [Accepted: 07/15/2013] [Indexed: 10/26/2022]
Abstract
The main functions of the kidney are to excrete metabolic waste products and actively reabsorb essential molecules such as amino acids, ions, glucose and water. In humans, a wide range of genetic disorders exist characterized by wasting of metabolically important compounds. At the cellular level, more than 20 highly specialized renal epithelial cell types located in different segments of the nephron contribute to the reabsorption process. In particular, proximal tubular cells play a crucial role and are uniquely adapted to maximize reabsorption efficiency. They accommodate high numbers of transporters and channels by increasing the apical surface area in contact with the primary filtrate by forming a brush border as well as undergoing hypertrophy and hyperplasia. This adaptation is evolutionarily conserved and is detected in the primitive pronephric kidney of fish and amphibians as well as the metanephric kidney of higher vertebrates. Surprisingly, signaling pathways regulating these three processes have remained largely unknown. Here we summarize recent studies that highlight the early phases of kidney development as a critical juncture in establishing proximal tubule size.
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