1
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Walker V. The Intricacies of Renal Phosphate Reabsorption-An Overview. Int J Mol Sci 2024; 25:4684. [PMID: 38731904 PMCID: PMC11083860 DOI: 10.3390/ijms25094684] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2024] [Revised: 04/17/2024] [Accepted: 04/19/2024] [Indexed: 05/13/2024] Open
Abstract
To maintain an optimal body content of phosphorus throughout postnatal life, variable phosphate absorption from food must be finely matched with urinary excretion. This amazing feat is accomplished through synchronised phosphate transport by myriads of ciliated cells lining the renal proximal tubules. These respond in real time to changes in phosphate and composition of the renal filtrate and to hormonal instructions. How they do this has stimulated decades of research. New analytical techniques, coupled with incredible advances in computer technology, have opened new avenues for investigation at a sub-cellular level. There has been a surge of research into different aspects of the process. These have verified long-held beliefs and are also dramatically extending our vision of the intense, integrated, intracellular activity which mediates phosphate absorption. Already, some have indicated new approaches for pharmacological intervention to regulate phosphate in common conditions, including chronic renal failure and osteoporosis, as well as rare inherited biochemical disorders. It is a rapidly evolving field. The aim here is to provide an overview of our current knowledge, to show where it is leading, and where there are uncertainties. Hopefully, this will raise questions and stimulate new ideas for further research.
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Affiliation(s)
- Valerie Walker
- Department of Clinical Biochemistry, University Hospital Southampton NHS Foundation Trust, Southampton General Hospital, Southampton S016 6YD, UK
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2
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Khundmiri SJ, Ecelbarger CM, Amponsem J, Ji H, Sandberg K, Lee DL. PPAR-α knockout leads to elevated blood pressure response to angiotensin II infusion associated with an increase in renal α-1 Na +/K + ATPase protein expression and activity. Life Sci 2022; 296:120444. [PMID: 35245523 PMCID: PMC8969884 DOI: 10.1016/j.lfs.2022.120444] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Revised: 02/15/2022] [Accepted: 02/26/2022] [Indexed: 01/13/2023]
Abstract
Peroxisome proliferator activated receptor alpha (PPAR-α) deletion has been shown to increase blood pressure (BP). We hypothesized that the BP increase in PPAR-α KO mice was mediated by increased expression and activity of basolateral Na+/K+ ATPase (NKA) pump. To address this hypothesis, we treated wild-type (WT) and PPAR-α knockout (KO) mice with a slow-pressor dose of angiotensin II (400 ng/kg·min) for 12 days by osmotic minipump. Radiotelemetry showed no significant differences in baseline mean arterial pressure (MAP) between WT and PPAR-α KO mice; however, by day 12 of infusion, MAP was significantly higher in PPAR-α KO mice (156 ± 16) compared to WT mice (138 ± 11 mmHg). NKA activity and protein expression (α1 subunit) were significantly higher in PPAR-α KO mice compared to WT mice. There was no significant difference in NKA mRNA levels. Angiotensin II further increased the expression and activity of the NKA in both genotypes along with the water channel, aquaporin 1 (Aqp1). In contrast, angiotensin II decreased the expression (64-97% reduction in band density) of sodium‑hydrogen exchanger-3 (NHE3), NHE regulatory factor-1 (NHERF1, Slc9a3r1), sodium‑potassium-2-chloride cotransporter (NKCC2), and epithelial sodium channel (ENaC) β- and γ- subunits in the renal cortex of both WT and PPAR-α KO mice, with no difference between genotypes. The sodium-chloride cotransporter (NCC) was also decreased by angiotensin II, but significantly more in PPAR-α KO (59% WT versus 77% KO reduction from their respective vehicle-treated mice). Our results suggest that PPAR-α attenuates angiotensin II-mediated increased blood pressure potentially via reducing expression and activity of the NKA.
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Affiliation(s)
- Syed J Khundmiri
- Department of Physiology and Biophysics, College of Medicine, Howard University, Washington, DC, USA.
| | - Carolyn M Ecelbarger
- Division of Endocrinology and Metabolism, Department of Medicine, Georgetown University Washington, DC, USA
| | - Joycemary Amponsem
- Department of Physiology and Biophysics, College of Medicine, Howard University, Washington, DC, USA
| | - Hong Ji
- Department of Medicine, Georgetown University Washington, DC, USA
| | - Kathryn Sandberg
- Department of Medicine, Georgetown University Washington, DC, USA
| | - Dexter L Lee
- Department of Physiology and Biophysics, College of Medicine, Howard University, Washington, DC, USA.
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3
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Ovejero D, Hartley IR, de Castro Diaz LF, Theng E, Li X, Gafni RI, Collins MT. PTH and FGF23 Exert Interdependent Effects on Renal Phosphate Handling: Evidence From Patients With Hypoparathyroidism and Hyperphosphatemic Familial Tumoral Calcinosis Treated With Synthetic Human PTH 1-34. J Bone Miner Res 2022; 37:179-184. [PMID: 34464000 DOI: 10.1002/jbmr.4429] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Revised: 08/12/2021] [Accepted: 08/16/2021] [Indexed: 12/27/2022]
Abstract
Parathyroid hormone (PTH) and fibroblast growth factor 23 (FGF23) both influence blood phosphate levels by regulating urinary phosphate reabsorption. Clinical data suggest that adequate renal phosphate handling requires the presence of both FGF23 and PTH, but robust evidence is lacking. To investigate whether the phosphaturic effects of PTH and FGF23 are interdependent, 11 patients with hypoparathyroidism, which features high blood phosphate in spite of concomitant FGF23 elevation, and 1 patient with hyperphosphatemic familial tumoral calcinosis (HFTC), characterized by deficient intact FGF23 action and resulting hyperphosphatemia, were treated with synthetic human PTH 1-34 (hPTH 1-34). Biochemical parameters, including blood phosphate, calcium, intact FGF23 (iFGF23), nephrogenic cAMP, 1,25(OH)2 vitamin D (1,25D), and tubular reabsorption of phosphate (TRP), were measured at baseline and after hPTH 1-34 treatment. In patients with hypoparathyroidism, administration of hPTH 1-34 increased nephrogenic cAMP, which resulted in serum phosphate normalization followed by a significant decrease in iFGF23. TRP initially decreased and returned to baseline. In the patient with HFTC, hPTH 1-34 administration also increased nephrogenic cAMP, but this did not produce changes in phosphate or TRP. No changes in calcium were observed in any of the studied patients, although prolonged hPTH 1-34 treatment did induce supraphysiologic 1,25D levels in the patient with HFTC. Our results indicate that PTH and FGF23 effects on phosphate regulation are interdependent and both are required to adequately regulate renal phosphate handling. Published 2021. This article is a U.S. Government work and is in the public domain in the USA.
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Affiliation(s)
- Diana Ovejero
- Skeletal Disorders and Mineral Homeostasis Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA.,Musculoskeletal Research Unit, Hospital del Mar Medical Research Institute, Centro de Investigación Biomédica en Red de Fragilidad y Envejecimiento Saludable (CIBERFES), Barcelona, Spain
| | - Iris R Hartley
- Skeletal Disorders and Mineral Homeostasis Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA
| | - Luis Fernandez de Castro Diaz
- Skeletal Disorders and Mineral Homeostasis Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA
| | - Elizabeth Theng
- Skeletal Disorders and Mineral Homeostasis Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA
| | - Xiaobai Li
- Biostatistics and Clinical Epidemiology Services (XL), National Institutes of Health, Bethesda, MD, USA
| | - Rachel I Gafni
- Skeletal Disorders and Mineral Homeostasis Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA
| | - Michael T Collins
- Skeletal Disorders and Mineral Homeostasis Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA
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4
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Küng CJ, Haykir B, Schnitzbauer U, Egli-Spichtig D, Hernando N, Wagner CA. Fibroblast growth factor 23 leads to endolysosomal routing of the renal phosphate cotransporters NaPi-IIa and NaPi-IIc in vivo. Am J Physiol Renal Physiol 2021; 321:F785-F798. [PMID: 34719948 DOI: 10.1152/ajprenal.00250.2021] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Na+-dependent phosphate cotransporters NaPi-IIa and NaPi-IIc, located at the brush-border membrane of renal proximal tubules, are regulated by numerous factors, including fibroblast growth factor 23 (FGF23). FGF23 downregulates NaPi-IIa and NaPi-IIc abundance after activating a signaling pathway involving phosphorylation of ERK1/2 (phospho-ERK1/2). FGF23 also downregulates expression of renal 1-α-hydroxylase (Cyp27b1) and upregulates 24-hydroxylase (Cyp24a1), thus reducing plasma calcitriol levels. Here, we examined the time course of FGF23-induced internalization of NaPi-IIa and NaPi-IIc and their intracellular pathway toward degradation in vivo. Mice were injected intraperitoneally with recombinant human (rh)FGF23 in the absence (biochemical analysis) or presence (immunohistochemistry) of leupeptin, an inhibitor of lysosomal proteases. Phosphorylation of ERK1/2 was enhanced 60 min after rhFGF23 administration, and increased phosphorylation was still detected 480 min after injection. Colocalization of phospho-ERK1/2 with NaPi-IIa was seen at 60 and 120 min and partly at 480 min. The abundance of both cotransporters was reduced 240 min after rhFGF23 administration, with a further reduction at 480 min. NaPi-IIa and NaPi-IIc were found to colocalize with clathrin and early endosomal antigen 1 as early as 120 min after rhFGF23 injection. Both cotransporters partially colocalized with cathepsin B and lysosomal-associated membrane protein-1, markers of lysosomes, 120 min after rhFGF23 injection. Thus, NaPi-IIa and NaPi-IIc are internalized within 2 h upon rhFGF23 injection. Both cotransporters share the pathway of clathrin-mediated endocytosis that leads first to early endosomes, finally resulting in trafficking toward the lysosome as early as 120 min after rhFGF23 administration.NEW & NOTEWORTHY The hormone fibroblast growth factor 23 (FGF23) controls phosphate homeostasis by regulating renal phosphate excretion. FGF23 acts on several phosphate transporters in the kidney. Here, we define the time course of this action and demonstrate how phosphate transporters NaPi-IIa and NaPi-IIc are internalized.
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Affiliation(s)
- Catharina J Küng
- Institute of Physiology, University of Zurich and National Center of Competence in Research Kidney.CH, Zurich, Switzerland
| | - Betül Haykir
- Institute of Physiology, University of Zurich and National Center of Competence in Research Kidney.CH, Zurich, Switzerland
| | - Udo Schnitzbauer
- Institute of Physiology, University of Zurich and National Center of Competence in Research Kidney.CH, Zurich, Switzerland
| | - Daniela Egli-Spichtig
- Institute of Physiology, University of Zurich and National Center of Competence in Research Kidney.CH, Zurich, Switzerland
| | - Nati Hernando
- Institute of Physiology, University of Zurich and National Center of Competence in Research Kidney.CH, Zurich, Switzerland
| | - Carsten A Wagner
- Institute of Physiology, University of Zurich and National Center of Competence in Research Kidney.CH, Zurich, Switzerland
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5
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Irsik DL, Bollag WB, Isales CM. Renal Contributions to Age-Related Changes in Mineral Metabolism. JBMR Plus 2021; 5:e10517. [PMID: 34693188 PMCID: PMC8520061 DOI: 10.1002/jbm4.10517] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Revised: 04/28/2021] [Accepted: 05/09/2021] [Indexed: 11/10/2022] Open
Abstract
Aging results in a general decline in function in most systems. This is particularly true with respect to the skeleton and renal systems, impacting mineral homeostasis. Calcium and phosphate regulation requires tight coordination among the intestine, bone, parathyroid gland, and kidney. The role of the intestine is to absorb calcium and phosphate from the diet. The bone stores or releases calcium and phosphate depending on the body's needs. In response to low plasma ionized calcium concentration, the parathyroid gland produces parathyroid hormone, which modulates bone turnover. The kidney reabsorbs or excretes the minerals and serves as the final regulator of plasma concentration. Many hormones are involved in this process in addition to parathyroid hormone, including fibroblast growth factor 23 produced by the bone and calcitriol synthesized by the kidney. Sclerostin, calcitonin, osteoprotegerin, and receptor activator of nuclear factor‐κB ligand also contribute to tissue‐specific regulation. Changes in the function of organs due to aging or disease can perturb this balance. During aging, the intestine cannot absorb calcium efficiently due to decreased expression of key proteins. In the bone, the balance between bone formation and bone resorption tends toward the latter in older individuals. The kidney may not filter blood as efficiently in the later decades of life, and the expression of certain proteins necessary for mineral homeostasis declines with age. These changes often lead to dysregulation of organismal mineral homeostasis. This review will focus on how mineral homeostasis is impacted by aging with a particular emphasis on the kidney's role in this process. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.
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Affiliation(s)
- Debra L Irsik
- Charlie Norwood VA Medical Center Augusta GA USA.,Department of Neuroscience and Regenerative Medicine Augusta University Augusta GA USA
| | - Wendy B Bollag
- Charlie Norwood VA Medical Center Augusta GA USA.,Department of Physiology Augusta University Augusta GA USA
| | - Carlos M Isales
- Department of Neuroscience and Regenerative Medicine Augusta University Augusta GA USA.,Division of Endocrinology, Department of Medicine Augusta University Augusta GA USA
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6
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Bird RP, Eskin NAM. The emerging role of phosphorus in human health. ADVANCES IN FOOD AND NUTRITION RESEARCH 2021; 96:27-88. [PMID: 34112356 DOI: 10.1016/bs.afnr.2021.02.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Phosphorus, an essential nutrient, performs vital functions in skeletal and non-skeletal tissues and is pivotal for energy production. The last two decades of research on the physiological importance of phosphorus have provided several novel insights about its dynamic nature as a nutrient performing functions as a phosphate ion. Phosphorous also acts as a signaling molecule and induces complex physiological responses. It is recognized that phosphorus homeostasis is critical for health. The intake of phosphorus by the general population world-wide is almost double the amount required to maintain health. This increase is attributed to the incorporation of phosphate containing food additives in processed foods purchased by consumers. Research findings assessed the impact of excessive phosphorus intake on cells' and organs' responses, and highlighted the potential pathogenic consequences. Research also identified a new class of bioactive phosphates composed of polymers of phosphate molecules varying in chain length. These polymers are involved in metabolic responses including hemostasis, brain and bone health, via complex mechanism(s) with positive or negative health effects, depending on their chain length. It is amazing, that phosphorus, a simple element, is capable of exerting multiple and powerful effects. The role of phosphorus and its polymers in the renal and cardiovascular system as well as on brain health appear to be important and promising future research directions.
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Affiliation(s)
- Ranjana P Bird
- School of Health Sciences, University of Northern British Columbia, Prince George, BC, Canada.
| | - N A Michael Eskin
- Department of Food and Human Nutritional Sciences, Faculty of Agricultural and Food Sciences, University of Manitoba, Winnipeg, MB, Canada
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7
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Zhang JY, You HZ, Wang MJ, Zhang Q, Dong XY, Liu JF, Chen J. High-phosphorus diet controlled for sodium elevates blood pressure in healthy adults via volume expansion. J Clin Hypertens (Greenwich) 2021; 23:849-859. [PMID: 33486869 PMCID: PMC8678725 DOI: 10.1111/jch.14182] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Revised: 12/23/2020] [Accepted: 01/03/2021] [Indexed: 01/26/2023]
Abstract
Whether increasing exposure to dietary phosphorus can lead to adverse clinical outcomes in healthy people is not clear. In this open‐label prospective cross‐over study, we are to explore the impact of various dietary phosphorus intake on mineral, sodium metabolisms and blood pressure in young healthy adults. There were 3 separate study periods of 5 days, each with a 5 days washout period between different diets interventions. Six young healthy male volunteers with normal nutrition status were recruited in Phase I Clinical Research Center and sequentially exposed to the following diets: (a) normal‐phosphorus diet (NPD): 1500 mg/d, (b) low‐phosphorus diet (LPD): 500 mg/d, (c) high‐phosphorus diet (HPD): 2300 mg/d. HPD induced a significant rise in daily average serum phosphate (1.47 ± 0.02 mmol/L [4.56 ± 0.06 mg/dl]) compared to NPD (1.34 ± 0.02 mmol/L [4.15 ± 0.06 mg/dL]) and LPD (1.17 ± 0.02 mmol/L [3.63 ± 0.06 mg/dL]) (p < .05). Daily average levels of serum parathyroid hormone and fibroblast growth factor 23 in HPD were significantly higher, and serum 1,25(OH)2D3 was remarkably lower than those in LPD. HPD induced a significant decrease in daily average serum aldosterone and an increase in daily average atrial natriuretic peptide level compared to LPD. The 24‐hour urine volume in HPD subjects was less than that in LPD subjects. HPD significantly increased daily average systolic blood pressure by 6.02 ± 1.24 mm Hg compared to NPD and by 8.58 ± 1.24mm Hg compared to LPD (p < .05). Our study provides the first evidence that 5‐day high‐phosphorus diet can induce elevation in SBP in young healthy adults, which may due to volume expansion.
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Affiliation(s)
- Jia-Ying Zhang
- Division of Nephrology, Huashan Hospital, Fudan University, Shanghai, China.,Division of Nutrition, Huashan Hospital, Fudan University, Shanghai, China.,National Clinical Research Center for Aging and Medicine, Huashan Hospital, Fudan University, Shanghai, China
| | - Huai-Zhou You
- Division of Nephrology, Huashan Hospital, Fudan University, Shanghai, China.,National Clinical Research Center for Aging and Medicine, Huashan Hospital, Fudan University, Shanghai, China
| | - Meng-Jing Wang
- Division of Nephrology, Huashan Hospital, Fudan University, Shanghai, China.,National Clinical Research Center for Aging and Medicine, Huashan Hospital, Fudan University, Shanghai, China
| | - Qian Zhang
- Division of Nephrology, Huashan Hospital, Fudan University, Shanghai, China.,National Clinical Research Center for Aging and Medicine, Huashan Hospital, Fudan University, Shanghai, China
| | - Xin-Yu Dong
- Division of Nephrology, Huashan Hospital, Fudan University, Shanghai, China
| | - Jing-Fang Liu
- Division of Nutrition, Huashan Hospital, Fudan University, Shanghai, China.,National Clinical Research Center for Aging and Medicine, Huashan Hospital, Fudan University, Shanghai, China
| | - Jing Chen
- Division of Nephrology, Huashan Hospital, Fudan University, Shanghai, China.,National Clinical Research Center for Aging and Medicine, Huashan Hospital, Fudan University, Shanghai, China
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8
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Abstract
Phosphate is an essential nutrient for life and is a critical component of bone formation, a major signaling molecule, and structural component of cell walls. Phosphate is also a component of high-energy compounds (i.e., AMP, ADP, and ATP) and essential for nucleic acid helical structure (i.e., RNA and DNA). Phosphate plays a central role in the process of mineralization, normal serum levels being associated with appropriate bone mineralization, while high and low serum levels are associated with soft tissue calcification. The serum concentration of phosphate and the total body content of phosphate are highly regulated, a process that is accomplished by the coordinated effort of two families of sodium-dependent transporter proteins. The three isoforms of the SLC34 family (SLC34A1-A3) show very restricted tissue expression and regulate intestinal absorption and renal excretion of phosphate. SLC34A2 also regulates the phosphate concentration in multiple lumen fluids including milk, saliva, pancreatic fluid, and surfactant. Both isoforms of the SLC20 family exhibit ubiquitous expression (with some variation as to which one or both are expressed), are regulated by ambient phosphate, and likely serve the phosphate needs of the individual cell. These proteins exhibit similarities to phosphate transporters in nonmammalian organisms. The proteins are nonredundant as mutations in each yield unique clinical presentations. Further research is essential to understand the function, regulation, and coordination of the various phosphate transporters, both the ones described in this review and the phosphate transporters involved in intracellular transport.
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Affiliation(s)
- Nati Hernando
- University of Zurich-Irchel, Institute of Physiology, Zurich, Switzerland; Department of Medicine, University of Louisville School of Medicine, Louisville, Kentucky; and Robley Rex VA Medical Center, Louisville, Kentucky
| | - Kenneth Gagnon
- University of Zurich-Irchel, Institute of Physiology, Zurich, Switzerland; Department of Medicine, University of Louisville School of Medicine, Louisville, Kentucky; and Robley Rex VA Medical Center, Louisville, Kentucky
| | - Eleanor Lederer
- University of Zurich-Irchel, Institute of Physiology, Zurich, Switzerland; Department of Medicine, University of Louisville School of Medicine, Louisville, Kentucky; and Robley Rex VA Medical Center, Louisville, Kentucky
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9
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Song GJ, Gupta DP, Rahman MH, Park HT, Al Ghouleh I, Bisello A, Lee MG, Park JY, Park HH, Jun JH, Chung KW, Choi BO, Suk K. Loss-of-function of EBP50 is a new cause of hereditary peripheral neuropathy: EBP50 functions in peripheral nerve system. Glia 2020; 68:1794-1809. [PMID: 32077526 DOI: 10.1002/glia.23805] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Revised: 02/04/2020] [Accepted: 02/07/2020] [Indexed: 12/12/2022]
Abstract
Finding causative genetic mutations is important in the diagnosis and treatment of hereditary peripheral neuropathies. This study was conducted to find new genes involved in the pathophysiology of hereditary peripheral neuropathy. We identified a new mutation in the EBP50 gene, which is co-segregated with neuropathic phenotypes, including motor and sensory deficit in a family with Charcot-Marie-Tooth disease. EBP50 is known to be important for the formation of microvilli in epithelial cells, and the discovery of this gene mutation allowed us to study the function of EBP50 in the nervous system. EBP50 was strongly expressed in the nodal and paranodal regions of sciatic nerve fibers, where Schwann cell microvilli contact the axolemma, and at the growth tips of primary Schwann cells. In addition, EBP50 expression was decreased in mouse models of peripheral neuropathy. Knockout mice were used to study EBP50 function in the peripheral nervous system. Interestingly motor function deficit and abnormal histology of nerve fibers were observed in EBP50+/- heterozygous mice at 12 months of age, but not 3 months. in vitro studies using Schwann cells showed that NRG1-induced AKT activation and migration were significantly reduced in cells overexpressing the I325V mutant of EBP50 or cells with knocked-down EBP50 expression. In conclusion, we show for the first time that loss of function due to EBP50 gene deficiency or mutation can cause peripheral neuropathy.
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Affiliation(s)
- Gyun Jee Song
- Department of Medical Science, Institute for Bio-Medical Convergence, Catholic Kwandong University, International St. Mary's Hospital, Incheon, Republic of Korea
| | - Deepak Prasad Gupta
- Department of Pharmacology, Brain Science and Engineering Institute, BK21 Plus KNU Biomedical Convergence Program, School of Medicine, Kyungpook National University, Daegu, Republic of Korea
| | - Md Habibur Rahman
- Department of Pharmacology, Brain Science and Engineering Institute, BK21 Plus KNU Biomedical Convergence Program, School of Medicine, Kyungpook National University, Daegu, Republic of Korea
| | - Hwan Tae Park
- Department of Molecular Neuroscience, College of Medicine, Dong-A University, Busan, Republic of Korea
| | - Imad Al Ghouleh
- Division of Cardiology, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Alessandro Bisello
- Department of Pharmacology and Chemical Biology, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania
| | - Maan-Gee Lee
- Department of Pharmacology, Brain Science and Engineering Institute, BK21 Plus KNU Biomedical Convergence Program, School of Medicine, Kyungpook National University, Daegu, Republic of Korea
| | - Jae-Yong Park
- School of Biosystems and Biomedical Sciences, College of Health Sciences, Korea University, Seoul, Republic of Korea
| | - Hyun Ho Park
- College of Pharmacy, Chung-Ang University, Seoul, Republic of Korea
| | - Jin Hyun Jun
- Department of Senior Healthcare, BK21 Plus Program, Graduate School of Eulji University, Department of Biomedical Laboratory Science, College of Health Science, Eulji University, Seongnam, Republic of Korea
| | - Ki Wha Chung
- Department of Biological Sciences, Kongju National University, Gongju, Republic of Korea
| | - Byung-Ok Choi
- Department of Neurology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea
| | - Kyoungho Suk
- Department of Pharmacology, Brain Science and Engineering Institute, BK21 Plus KNU Biomedical Convergence Program, School of Medicine, Kyungpook National University, Daegu, Republic of Korea
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10
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Pushpakumar S, Ahmad A, Ketchem CJ, Jose PA, Weinman EJ, Sen U, Lederer ED, Khundmiri SJ. Sodium-hydrogen exchanger regulatory factor-1 (NHERF1) confers salt sensitivity in both male and female models of hypertension in aging. Life Sci 2020; 243:117226. [PMID: 31904366 PMCID: PMC7015806 DOI: 10.1016/j.lfs.2019.117226] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2019] [Revised: 12/16/2019] [Accepted: 12/23/2019] [Indexed: 01/11/2023]
Abstract
Hypertension is a risk factor for premature death and roughly 50% of hypertensive patients are salt-sensitive. The incidence of salt-sensitive hypertension increases with age. However, the mechanisms of salt-sensitive hypertension are not well understood. We had demonstrated decreased renal sodium‑hydrogen exchanger regulatory factor 1 (NHERF1) expression in old salt-resistant F344 rats. Based on those studies we hypothesized that NHERF1 expression is required for the development of some forms of salt-sensitive hypertension. To address this hypothesis, we measured blood pressure in NHERF1 expressing salt-sensitive 4-mo and 24-mo-old male and female Fischer Brown Norway (FBN) rats male and female 18-mo-old NHERF1 knock-out (NHERF1-/-) mice and wild-type (WT) littermates on C57BL/6J background after feeding high salt (8% NaCl) diet for 7 days. Our data demonstrate that 8% salt diet increased blood pressure in both male and female 24-mo-old FBN rats but not in 4-mo-old FBN rats and in 18-mo-old male and female WT mice but not in NHERF1-/- mice. Renal dopamine 1 receptor (D1R) expression was decreased in 24-mo-old rats, compared with 4-mo-old FBN rats. However, sodium chloride cotransporter (NCC) expression increased in 24-mo-old FBN rats. In FBN rats, age had no effect on NaK ATPase α1 and NKCC2 expression. By contrast, high salt diet increased the renal expressions of NKCC2, and NCC in 24-mo-old FBN rats. High salt diet also increased NKCC2 and NCC expression in WT mice but not NHERF1-/- mice. Our data suggest that renal NHERF1 expression confers salt sensitivity with aging, associated with increased expression of sodium transporters.
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Affiliation(s)
- Sathnur Pushpakumar
- Department of Physiology, University of Louisville, Louisville, KY, United States of America
| | - Asrar Ahmad
- Department of Physiology and Biophysics, Howard University College of Medicine, Washington, DC, United States of America
| | - Corey J Ketchem
- Department of Medicine, Nephrology and Hypertension, University of Louisville, Louisville, KY, United States of America
| | - Pedro A Jose
- Department of Medicine, Division of Renal Diseases and Hypertension, The George Washington University, Washington, DC, United States of America
| | - Edward J Weinman
- Department of Medicine, University of Maryland School of Medicine, Baltimore, MD, United States of America
| | - Utpal Sen
- Department of Physiology, University of Louisville, Louisville, KY, United States of America
| | - Eleanor D Lederer
- Department of Physiology, University of Louisville, Louisville, KY, United States of America; Department of Medicine, Nephrology and Hypertension, University of Louisville, Louisville, KY, United States of America; Robley Rex VA Medical Center, Louisville, KY, United States of America
| | - Syed J Khundmiri
- Department of Physiology and Biophysics, Howard University College of Medicine, Washington, DC, United States of America.
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11
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Bushau-Sprinkle AM, Lederer ED. New roles of the Na +/H + exchange regulatory factor 1 scaffolding protein: a review. Am J Physiol Renal Physiol 2020; 318:F804-F808. [PMID: 31984791 DOI: 10.1152/ajprenal.00467.2019] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Na+/H+ exchange regulatory factor 1 (NHERF1), a member of a PDZ scaffolding protein family, was first identified as an organizer of membrane-bound protein complexes composed of hormone receptors, signal transduction pathways, and electrolyte and mineral transporters and channels. NHERF1 is involved in the regulation of Na+/H+ exchanger 3, Na+-dependent phosphate transporter 2a, and Na+-K+-ATPase through its ability to scaffold these transporters to the plasma membrane, allowing regulation of these protein complexes with their associated hormone receptors. Recently, NHERF1 has received increased interest in its involvement in a variety of functions, including cell structure and trafficking, tumorigenesis and tumor behavior, inflammatory responses, and tissue injury. In this review, we highlight the evidence for the expansive role of NHERF1 in cell biology and speculate on the implications for renal physiology and pathophysiology.
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Affiliation(s)
- Adrienne M Bushau-Sprinkle
- Department of Pharmacology and Toxicology, University of Louisville, Louisville, Kentucky.,Robley Rex Veterans Affairs Medical Center, Louisville, Kentucky
| | - Eleanor D Lederer
- Division of Nephrology, Department of Medicine, University of Louisville, Louisville, Kentucky.,Robley Rex Veterans Affairs Medical Center, Louisville, Kentucky
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12
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Martins JS, Liu ES, Sneddon WB, Friedman PA, Demay MB. 1,25-Dihydroxyvitamin D Maintains Brush Border Membrane NaPi2a and Attenuates Phosphaturia in Hyp Mice. Endocrinology 2019; 160:2204-2214. [PMID: 31237611 PMCID: PMC6735734 DOI: 10.1210/en.2019-00186] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Accepted: 06/19/2019] [Indexed: 12/21/2022]
Abstract
Phosphate homeostasis is critical for many cellular processes and is tightly regulated. The sodium-dependent phosphate cotransporter, NaPi2a, is the major regulator of urinary phosphate reabsorption in the renal proximal tubule. Its activity is dependent upon its brush border localization that is regulated by fibroblast growth factor 23 (FGF23) and PTH. High levels of FGF23, as are seen in the Hyp mouse model of human X-linked hypophosphatemia, lead to renal phosphate wasting. Long-term treatment of Hyp mice with 1,25-dihydroxyvitamin D (1,25D) or 1,25D analogues has been shown to improve renal phosphate wasting in the setting of increased FGF23 mRNA expression. Studies were undertaken to define the cellular and molecular basis for this apparent FGF23 resistance. 1,25D increased FGF23 protein levels in the cortical bone and circulation of Hyp mice but did not impair FGF23 cleavage. 1,25D attenuated urinary phosphate wasting as early as one hour postadministration, without suppressing FGF23 receptor/coreceptor expression. Although 1,25D treatment induced expression of early growth response 1, an early FGF23 responsive gene required for its phosphaturic effects, it paradoxically enhanced renal phosphate reabsorption and NaPi2a protein expression in renal brush border membranes (BBMs) within one hour. The Na-H+ exchange regulatory factor 1 (NHERF1) is a scaffolding protein thought to anchor NaPi2a to the BBM. Although 1,25D did not alter NHERF1 protein levels acutely, it enhanced NHERF1-NaPi2a interactions in Hyp mice. 1,25D also prevented the decrease in NHERF1/NaPi2a interactions in PTH-treated wild-type mice. Thus, these investigations identify a novel role for 1,25D in the hormonal regulation of renal phosphate handling.
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Affiliation(s)
- Janaina S Martins
- Endocrine Unit, Massachusetts General Hospital, Boston, Massachusetts
- Harvard Medical School, Boston, Massachusetts
| | - Eva S Liu
- Endocrine Unit, Massachusetts General Hospital, Boston, Massachusetts
- Harvard Medical School, Boston, Massachusetts
- Division of Endocrinology Diabetes and Hypertension, Brigham and Women’s Hospital, Boston, Massachusetts
| | - W Bruce Sneddon
- Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Peter A Friedman
- Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Marie B Demay
- Endocrine Unit, Massachusetts General Hospital, Boston, Massachusetts
- Harvard Medical School, Boston, Massachusetts
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13
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Anglani F, Gianesello L, Beara-Lasic L, Lieske J. Dent disease: A window into calcium and phosphate transport. J Cell Mol Med 2019; 23:7132-7142. [PMID: 31472005 PMCID: PMC6815805 DOI: 10.1111/jcmm.14590] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Revised: 07/22/2019] [Accepted: 07/24/2019] [Indexed: 12/19/2022] Open
Abstract
This review examines calcium and phosphate transport in the kidney through the lens of the rare X-linked genetic disorder Dent disease. Dent disease type 1 (DD1) is caused by mutations in the CLCN5 gene encoding ClC-5, a Cl- /H+ antiporter localized to early endosomes of the proximal tubule (PT). Phenotypic features commonly include low molecular weight proteinuria (LMWP), hypercalciuria, focal global sclerosis and chronic kidney disease; calcium nephrolithiasis, nephrocalcinosis and hypophosphatemic rickets are less commonly observed. Although it is not surprising that abnormal endosomal function and recycling in the PT could result in LMWP, it is less clear how ClC-5 dysfunction disturbs calcium and phosphate metabolism. It is known that the majority of calcium and phosphate transport occurs in PT cells, and PT endocytosis is essential for calcium and phosphorus reabsorption in this nephron segment. Evidence from ClC-5 KO models suggests that ClC-5 mediates parathormone endocytosis from tubular fluid. In addition, ClC-5 dysfunction alters expression of the sodium/proton exchanger NHE3 on the PT apical surface thus altering transcellular sodium movement and hence paracellular calcium reabsorption. A potential role for NHE3 dysfunction in the DD1 phenotype has never been investigated, either in DD models or in patients with DD1, even though patients with DD1 exhibit renal sodium and potassium wasting, especially when exposed to even a low dose of thiazide diuretic. Thus, insights from the rare disease DD1 may inform possible underlying mechanisms for the phenotype of hypercalciuria and idiopathic calcium stones.
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Affiliation(s)
- Franca Anglani
- Division of Nephrology, Department of Medicine, Laboratory of Histomorphology and Molecular Biology of the Kidney, University of Padua, Padua, Italy
| | - Lisa Gianesello
- Division of Nephrology, Department of Medicine, Laboratory of Histomorphology and Molecular Biology of the Kidney, University of Padua, Padua, Italy
| | - Lada Beara-Lasic
- Division of Nephrology, New York University School of Medicine, New York, NY, USA
| | - John Lieske
- Division of Nephrology and Hypertension, Department of Medicine, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, USA
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14
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Abstract
Calcium kidney stones are common worldwide. Most are idiopathic and composed of calcium oxalate. Calcium phosphate is present in around 80% and may initiate stone formation. Stone production is multifactorial with a polygenic genetic contribution. Phosphaturia is found frequently among stone formers but until recently received scant attention. This review examines possible mechanisms for the phosphaturia and its relevance to stone formation from a wide angle. There is a striking lack of clinical data. Phosphaturia is associated, but not correlated, with hypercalciuria, increased 1,25 dihydroxy-vitamin D [1,25 (OH)2D], and sometimes evidence of disturbances in proximal renal tubular function. Phosphate reabsorption in the proximal renal tubules requires tightly regulated interaction of many proteins. Paracellular flow through intercellular tight junctions is the major route of phosphate absorption from the intestine and can be reduced therapeutically in hyperphosphatemic patients. In monogenic defects stones develop when phosphaturia is associated with hypercalciuria, generally explained by increased 1,25 (OH)2D production in response to hypophosphatemia. Calcification does not occur in disorders with increased FGF23 when phosphaturia occurs in isolation and 1,25 (OH)2D is suppressed. Candidate gene studies have identified mutations in the phosphate transporters, but in few individuals. One genome-wide study identified a polymorphism of the phosphate transporter gene SLC34A4 associated with stones. Others did not find mutations obviously linked to phosphate reabsorption. Future genetic studies should have a wide trawl and should focus initially on groups of patients with clearly defined phenotypes. The global data should be pooled.
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Affiliation(s)
- Valerie Walker
- Department of Clinical Biochemistry, University Hospital Southampton NHS Foundation Trust, Southampton, United Kingdom.
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15
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Hernando N. NaPi-IIa interacting partners and their (un)known functional roles. Pflugers Arch 2018; 471:67-82. [PMID: 30022249 DOI: 10.1007/s00424-018-2176-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Accepted: 06/26/2018] [Indexed: 01/14/2023]
Abstract
The sorting and stabilization of proteins at specific subcellular domains depend upon the formation of networks build up by specific protein-protein interactions. In addition, protein networks also ensure the specificity of many regulatory processes by bringing together regulatory molecules with their targets. Whereas the success on the identification of protein-protein interactions is (up to a point) technology-driven, the assignment of functional roles to specific partners remains a major challenge. This review summarizes the work that led to the identification of partners of the Na+/phosphate cotransporter NaPi-IIa as well as the effects of the interactions in the expression and/or regulation of the cotransporter.
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Affiliation(s)
- Nati Hernando
- Institute of Physiology, University Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland.
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16
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Barati MT, Ketchem CJ, Merchant ML, Kusiak WB, Jose PA, Weinman EJ, LeBlanc AJ, Lederer ED, Khundmiri SJ. Loss of NHERF-1 expression prevents dopamine-mediated Na-K-ATPase regulation in renal proximal tubule cells from rat models of hypertension: aged F344 rats and spontaneously hypertensive rats. Am J Physiol Cell Physiol 2017; 313:C197-C206. [PMID: 28515088 DOI: 10.1152/ajpcell.00219.2016] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Revised: 05/08/2017] [Accepted: 05/08/2017] [Indexed: 01/11/2023]
Abstract
Dopamine decreases Na-K-ATPase (NKA) activity by PKC-dependent phosphorylation and endocytosis of the NKA α1. Dopamine-mediated regulation of NKA is impaired in aging and some forms of hypertension. Using opossum (OK) proximal tubule cells (PTCs), we demonstrated that sodium-hydrogen exchanger regulatory factor-1 (NHERF-1) associates with NKA α1 and dopamine-1 receptor (D1R). This association is required for the dopamine-mediated regulation of NKA. In OK cells, dopamine decreases NHERF-1 association with NKA α1 but increases its association with D1R. However, it is not known whether NHERF-1 plays a role in dopamine-mediated NKA regulation in animal models of hypertension. We hypothesized that defective dopamine-mediated regulation of NKA results from the decrease in NHERF-1 expression in rat renal PTCs isolated from animal models of hypertension [spontaneously hypertensive rats (SHRs) and aged F344 rats]. To test this hypothesis, we isolated and cultured renal PTCs from 22-mo-old F344 rats and their controls, normotensive 4-mo-old F344 rats, and SHRs and their controls, normotensive Wistar-Kyoto (WKY) rats. The results demonstrate that in both hypertensive models (SHR and aged F344), NHERF-1 expression, dopamine-mediated phosphorylation of NKA, and ouabain-inhibitable K+ transport are reduced. Transfection of NHERF-1 into PTCs from aged F344 and SHRs restored dopamine-mediated inhibition of NKA. These results suggest that decreased renal NHERF-1 expression contributes to the impaired dopamine-mediated inhibition of NKA in PTCs from animal models of hypertension.
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Affiliation(s)
- Michelle T Barati
- Department of Medicine, Nephrology and Hypertension, University of Louisville, Louisville, Kentucky
| | - Corey J Ketchem
- Department of Medicine, Nephrology and Hypertension, University of Louisville, Louisville, Kentucky
| | - Michael L Merchant
- Department of Medicine, Nephrology and Hypertension, University of Louisville, Louisville, Kentucky
| | - Walter B Kusiak
- Department of Medicine, Nephrology and Hypertension, University of Louisville, Louisville, Kentucky
| | - Pedro A Jose
- Department of Medicine, Division of Renal Diseases and Hypertension, and Department of Pharmacology and Physiology, The George Washington University, Washington, District of Columbia
| | - Edward J Weinman
- Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland
| | - Amanda J LeBlanc
- Department of Physiology, University of Louisville, Louisville, Kentucky
| | - Eleanor D Lederer
- Department of Medicine, Nephrology and Hypertension, University of Louisville, Louisville, Kentucky.,Department of Physiology, University of Louisville, Louisville, Kentucky.,Robley Rex VA Medical Center, Louisville, Kentucky; and
| | - Syed J Khundmiri
- Department of Physiology and Biophysics, Howard University College of Medicine, Washington, District of Columbia
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17
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Fakhar M, Rashid S. Targeted inhibition of Klotho binding to fibroblast growth factor 23 prevents hypophosphetemia. J Mol Graph Model 2017; 75:9-19. [PMID: 28501532 DOI: 10.1016/j.jmgm.2017.04.024] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2017] [Revised: 04/13/2017] [Accepted: 04/18/2017] [Indexed: 02/08/2023]
Abstract
Klotho is a transmembrane protein which plays significant role in the pathogenesis of phosphate ion (Pi)-related disorders. Pi accumulation in human kidney tissues results in the major metabolic disorders due to malfunctioning of Klotho-FGFR1-FGF23 trimeric complex. The potential role of Klotho in Pi metabolism was elaborated through modeling and interaction analysis of glycosyl hydrolase (GS1 and GS2) domains with Fibroblast growth factor 23 (FGF23). In order to inhibit the association of Klotho and FGF23, binding patterns of three reported hits (N-(2-chlorophenyl)-1H-indole-3-carboxamide, N-[2-(1-cyclohexen-1-yl)ethyl]-6,7,8,9-tetrahydropyrido[1,2-e]purin-4-amine and 2-(1-propyl)amino-11-chlorothiazolo[5,4-a]acridine) were evaluated through molecular docking analysis. These inhibitors effectively targeted both GS1 and GS2 domains of Klotho at the similar sites required for FGF23 binding. To further characterize the comparative binding profile of these compounds, molecular dynamics simulation assays were performed. Taken together, current study emphasizes that Klotho may be anticipated as a target molecule in familial hypophosphatemic rickets and mentioned compounds may prove to be effective therapeutic targets against hypophosphetemia induced disorders.
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Affiliation(s)
- Muhammad Fakhar
- National Center for Bioinformatics, Quaid-i-Azam University, Islamabad, Pakistan
| | - Sajid Rashid
- National Center for Bioinformatics, Quaid-i-Azam University, Islamabad, Pakistan.
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18
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Kaneko I, Tatsumi S, Segawa H, Miyamoto KI. Control of phosphate balance by the kidney and intestine. Clin Exp Nephrol 2016; 21:21-26. [PMID: 27900568 DOI: 10.1007/s10157-016-1359-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2016] [Accepted: 11/07/2016] [Indexed: 01/06/2023]
Abstract
The prevention and correction of hyperphosphatemia are major goals of the treatment of chronic kidney disease (CKD)-bone mineral disorders, and thus, Pi balance requires special attention. Pi balance is maintained by intestinal absorption, renal excretion, and bone accretion. The kidney is mainly responsible for the plasma Pi concentration. In CKD, reduced glomerular filtration rate leads to various Pi metabolism abnormalities, and Pi absorption in the small intestine also has an important role in Pi metabolism. Disturbances in Pi metabolism are mediated by a series of complex changes in regulatory hormones originating from the skeleton, intestine, parathyroid gland, and kidney. In this review, we describe the regulation of type II sodium-dependent Pi co-transporters by the kidney and intestine, including the regulation of Pi transport, circadian rhythm, and the vicious circle between salivary Pi secretion and intestinal Pi absorption in animals with and without CKD.
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Affiliation(s)
- Ichiro Kaneko
- Department of Molecular Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, 3-18-15 Kuramoto-Cho, Tokushima, 770-8503, Japan
| | - Sawako Tatsumi
- Department of Molecular Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, 3-18-15 Kuramoto-Cho, Tokushima, 770-8503, Japan
| | - Hiroko Segawa
- Department of Molecular Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, 3-18-15 Kuramoto-Cho, Tokushima, 770-8503, Japan
| | - Ken-Ichi Miyamoto
- Department of Molecular Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, 3-18-15 Kuramoto-Cho, Tokushima, 770-8503, Japan.
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19
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Sakoh T, Nakayama M, Tsuchihashi T, Yoshitomi R, Tanaka S, Katafuchi E, Fukui A, Shikuwa Y, Anzai N, Kitazono T, Tsuruya K. Associations of fibroblast growth factor 23 with urate metabolism in patients with chronic kidney disease. Metabolism 2016; 65:1498-507. [PMID: 27621185 DOI: 10.1016/j.metabol.2016.07.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/15/2016] [Revised: 06/13/2016] [Accepted: 07/14/2016] [Indexed: 10/21/2022]
Abstract
OBJECTIVE In patients with preserved kidney function, a positive association of fibroblast growth factor 23 (FGF23) with serum uric acid (SUA) has been reported; however, the relationship in overall chronic kidney disease (CKD) patients has not been investigated. No report has examined the relationship between FGF23 and uric acid clearance (CUA). The aim of the present study was to determine whether FGF23 is independently associated with urate metabolism in patients with CKD stages 1-5. MATERIALS AND METHODS In this cross-sectional study, 537 CKD patients were enrolled. SUA, CUA, FGF23, parathyroid hormone (PTH), and 1,25-dihydroxyvitamin D (1,25(OH)2D) were measured. Multivariable linear regression analysis was applied to determine independent factors associated with SUA or CUA. RESULTS In all patients, both SUA and CUA were independently associated with male sex, use of diuretics, use of uric acid-lowering agents, estimated glomerular filtration rate, and log FGF23 (β=0.29, P<0.01 for SUA; β=-0.11, P<0.01 for CUA), but not with log PTH or log 1,25(OH)2D. Dyslipidemia and diabetes were also independent factors for SUA and CUA, respectively. In multivariable analyses by sex, log FGF23 was associated with SUA in both sexes (β=0.32, P<0.01 in males vs. β=0.20, P=0.02 in females). Conversely, log FGF23 was independently associated with CUA in males (β=-0.15, P<0.01), but not in females (β=-0.09, P=0.17). CONCLUSIONS FGF23 was independently associated with urate metabolism in this population of CKD patients. FGF23 might also have a stronger association with urate metabolism in males compared with females.
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Affiliation(s)
- Teppei Sakoh
- Division of Nephrology and Clinical Research Institute, Department of Internal Medicine, National Hospital Organization Kyushu Medical Center, 1-8-1 Jigyohama, Chuo-ku, Fukuoka 810-8563, Japan; Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
| | - Masaru Nakayama
- Division of Nephrology and Clinical Research Institute, Department of Internal Medicine, National Hospital Organization Kyushu Medical Center, 1-8-1 Jigyohama, Chuo-ku, Fukuoka 810-8563, Japan.
| | - Takuya Tsuchihashi
- Division of Hypertension, Department of Internal Medicine, Steel Memorial Yawata Hospital, 1-1-1 Harunomachi, Yahatahigashi-ku, Fukuoka 805-8508, Japan.
| | - Ryota Yoshitomi
- Division of Nephrology and Clinical Research Institute, Department of Internal Medicine, National Hospital Organization Kyushu Medical Center, 1-8-1 Jigyohama, Chuo-ku, Fukuoka 810-8563, Japan; Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
| | - Shigeru Tanaka
- Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan; Department of Internal Medicine, Fukuoka Dental College, 2-15-1 Tamura, Sawara-ku, Fukuoka 814-0193, Japan.
| | - Eisuke Katafuchi
- Division of Nephrology and Clinical Research Institute, Department of Internal Medicine, National Hospital Organization Kyushu Medical Center, 1-8-1 Jigyohama, Chuo-ku, Fukuoka 810-8563, Japan.
| | - Akiko Fukui
- Division of Nephrology and Clinical Research Institute, Department of Internal Medicine, National Hospital Organization Kyushu Medical Center, 1-8-1 Jigyohama, Chuo-ku, Fukuoka 810-8563, Japan.
| | - Yui Shikuwa
- Division of Nephrology and Clinical Research Institute, Department of Internal Medicine, National Hospital Organization Kyushu Medical Center, 1-8-1 Jigyohama, Chuo-ku, Fukuoka 810-8563, Japan.
| | - Naohiko Anzai
- Department of Pharmacology, Chiba University Graduate School of Medicine, 1-8-1 Inohana, Chuo-ku, Chiba 260-8670, Japan.
| | - Takanari Kitazono
- Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
| | - Kazuhiko Tsuruya
- Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan; Department of Integrated Therapy for Chronic Kidney Disease, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
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20
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Sneddon WB, Ruiz GW, Gallo LI, Xiao K, Zhang Q, Rbaibi Y, Weisz OA, Apodaca GL, Friedman PA. Convergent Signaling Pathways Regulate Parathyroid Hormone and Fibroblast Growth Factor-23 Action on NPT2A-mediated Phosphate Transport. J Biol Chem 2016; 291:18632-42. [PMID: 27432882 PMCID: PMC5009241 DOI: 10.1074/jbc.m116.744052] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2016] [Indexed: 12/18/2022] Open
Abstract
Parathyroid hormone (PTH) and FGF23 are the primary hormones regulating acute phosphate homeostasis. Human renal proximal tubule cells (RPTECs) were used to characterize the mechanism and signaling pathways of PTH and FGF23 on phosphate transport and the role of the PDZ protein NHERF1 in mediating PTH and FGF23 effects. RPTECs express the NPT2A phosphate transporter, αKlotho, FGFR1, FGFR3, FGFR4, and the PTH receptor. FGFR1 isoforms are formed from alternate splicing of exon 3 and of exon 8 or 9 in Ir-like loop 3. Exon 3 was absent, but mRNA containing both exons 8 and 9 is present in cytoplasm. Using an FGFR1c-specific antibody together with mass spectrometry analysis, we show that RPTECs express FGFR-β1C. The data are consistent with regulated FGFR1 splicing involving a novel cytoplasmic mechanism. PTH and FGF23 inhibited phosphate transport in a concentration-dependent manner. At maximally effective concentrations, PTH and FGF23 equivalently decreased phosphate uptake and were not additive, suggesting a shared mechanism of action. Protein kinase A or C blockade prevented PTH but not FGF23 actions. Conversely, inhibiting SGK1, blocking FGFR dimerization, or knocking down Klotho expression disrupted FGF23 actions but did not interfere with PTH effects. C-terminal FGF23(180-251) competitively and selectively blocked FGF23 action without disrupting PTH effects. However, both PTH and FGF23-sensitive phosphate transport were abolished by NHERF1 shRNA knockdown. Extended treatment with PTH or FGF23 down-regulated NPT2A without affecting NHERF1. We conclude that FGFR1c and PTHR signaling pathways converge on NHERF1 to inhibit PTH- and FGF23-sensitive phosphate transport and down-regulate NPT2A.
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MESH Headings
- Cell Line, Transformed
- Fibroblast Growth Factor-23
- Fibroblast Growth Factors/genetics
- Fibroblast Growth Factors/metabolism
- Glucuronidase/biosynthesis
- Glucuronidase/genetics
- Humans
- Klotho Proteins
- Parathyroid Hormone/genetics
- Parathyroid Hormone/metabolism
- Phosphates/metabolism
- Phosphoproteins/genetics
- Phosphoproteins/metabolism
- Receptor, Fibroblast Growth Factor, Type 1/genetics
- Receptor, Fibroblast Growth Factor, Type 1/metabolism
- Receptor, Fibroblast Growth Factor, Type 3/biosynthesis
- Receptor, Fibroblast Growth Factor, Type 3/genetics
- Receptor, Fibroblast Growth Factor, Type 4/biosynthesis
- Receptor, Fibroblast Growth Factor, Type 4/genetics
- Receptor, Parathyroid Hormone, Type 1/genetics
- Receptor, Parathyroid Hormone, Type 1/metabolism
- Signal Transduction/physiology
- Sodium-Hydrogen Exchangers/genetics
- Sodium-Hydrogen Exchangers/metabolism
- Sodium-Phosphate Cotransporter Proteins, Type IIa/genetics
- Sodium-Phosphate Cotransporter Proteins, Type IIa/metabolism
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Affiliation(s)
- W Bruce Sneddon
- From the Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology and
| | - Giovanni W Ruiz
- Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - Luciana I Gallo
- Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - Kunhong Xiao
- From the Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology and
| | - Qiangmin Zhang
- From the Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology and
| | - Youssef Rbaibi
- Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - Ora A Weisz
- Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261 Cell Biology, and
| | - Gerard L Apodaca
- Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261 Cell Biology, and
| | - Peter A Friedman
- From the Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology and the Departments of Structural Biology,
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21
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Abstract
Renal hyperparathyroidism (rHPT) is a common complication of chronic kidney disease characterized by elevated parathyroid hormone levels secondary to derangements in the homeostasis of calcium, phosphate, and vitamin D. Patients with rHPT experience increased rates of cardiovascular problems and bone disease. The Kidney Disease: Improving Global Outcomes guidelines recommend that screening and management of rHPT be initiated for all patients with chronic kidney disease stage 3 (estimated glomerular filtration rate, < 60 mL/min/1.73 m(2)). Since the 1990s, improving medical management with vitamin D analogs, phosphate binders, and calcimimetic drugs has expanded the treatment options for patients with rHPT, but some patients still require a parathyroidectomy to mitigate the sequelae of this challenging disease.
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Affiliation(s)
- Noah K Yuen
- Surgical Resident at the University of California, Davis in Sacramento.
| | - Shubha Ananthakrishnan
- Assistant Professor of Internal Medicine at the University of California, Davis in Sacramento.
| | - Michael J Campbell
- Assistant Professor in the Department of Surgery at the University of California, Davis in Sacramento.
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22
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A systematic evaluation of sorting motifs in the sodium–iodide symporter (NIS). Biochem J 2016; 473:919-28. [DOI: 10.1042/bj20151086] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Accepted: 02/01/2016] [Indexed: 01/08/2023]
Abstract
Human sodium–iodide symporter (NIS) variants were created to suppress predicted binding motifs potentially implicated in trafficking of this protein. A leucine residue in an internal PDZ-binding motif was found to be essential for expression of the symporter at the plasma membrane.
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23
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Abstract
PTH and Vitamin D are two major regulators of mineral metabolism. They play critical roles in the maintenance of calcium and phosphate homeostasis as well as the development and maintenance of bone health. PTH and Vitamin D form a tightly controlled feedback cycle, PTH being a major stimulator of vitamin D synthesis in the kidney while vitamin D exerts negative feedback on PTH secretion. The major function of PTH and major physiologic regulator is circulating ionized calcium. The effects of PTH on gut, kidney, and bone serve to maintain serum calcium within a tight range. PTH has a reciprocal effect on phosphate metabolism. In contrast, vitamin D has a stimulatory effect on both calcium and phosphate homeostasis, playing a key role in providing adequate mineral for normal bone formation. Both hormones act in concert with the more recently discovered FGF23 and klotho, hormones involved predominantly in phosphate metabolism, which also participate in this closely knit feedback circuit. Of great interest are recent studies demonstrating effects of both PTH and vitamin D on the cardiovascular system. Hyperparathyroidism and vitamin D deficiency have been implicated in a variety of cardiovascular disorders including hypertension, atherosclerosis, vascular calcification, and kidney failure. Both hormones have direct effects on the endothelium, heart, and other vascular structures. How these effects of PTH and vitamin D interface with the regulation of bone formation are the subject of intense investigation.
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Affiliation(s)
- Syed Jalal Khundmiri
- Department of Medicine, University of Louisville, Louisville, Kentucky, USA
- Department of Physiology and Biophysics, University of Louisville, Louisville, Kentucky, USA
| | - Rebecca D. Murray
- Department of Medicine, University of Louisville, Louisville, Kentucky, USA
- Department of Physiology and Biophysics, University of Louisville, Louisville, Kentucky, USA
| | - Eleanor Lederer
- Department of Medicine, University of Louisville, Louisville, Kentucky, USA
- Department of Physiology and Biophysics, University of Louisville, Louisville, Kentucky, USA
- Robley Rex VA Medical Center, University of Louisville, Louisville, Kentucky, USA
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Ketchem CJ, Khundmiri SJ, Gaweda AE, Murray R, Clark BJ, Weinman EJ, Lederer ED. Role of Na+/H+ exchanger regulatory factor 1 in forward trafficking of the type IIa Na+-Pi cotransporter. Am J Physiol Renal Physiol 2015; 309:F109-19. [PMID: 25995109 DOI: 10.1152/ajprenal.00133.2015] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Na+/H+ exchanger regulatory factor (NHERF1) plays a critical role in the renal transport of phosphate by binding to Na+-Pi cotransporter (NpT2a) in the proximal tubule. While the association between NpT2a and NHERF1 in the apical membrane is known, the role of NHERF1 to regulate the trafficking of NpT2a has not been studied. To address this question, we performed cell fractionation by sucrose gradient centrifugation in opossum kidney (OK) cells placed in low-Pi medium to stimulate forward trafficking of NpT2a. Immunoblot analysis demonstrated expression of NpT2a and NHERF1 in the endoplasmic reticulum (ER)/Golgi. Coimmunoprecipitation demonstrated a NpT2a-NHERF1 interaction in the ER/Golgi. Low-Pi medium for 4 and 8 h triggered a decrease in NHERF1 in the plasma membrane with a corresponding increase in the ER/Golgi. Time-lapse total internal reflection fluorescence imaging of OK cells placed in low-Pi medium, paired with particle tracking and mean square displacement analysis, indicated active directed movement of NHERF1 at early and late time points, whereas NpT2a showed active movement only at later times. Silence of NHERF1 in OK cells expressing green fluorescent protein (GFP)-NpT2a resulted in an intracellular accumulation of GFP-NpT2a. Transfection with GFP-labeled COOH-terminal (TRL) PDZ-binding motif deleted or wild-type NpT2a in OK cells followed by cell fractionation and immunoprecipitation confirmed that the interaction between NpT2a and NHERF1 was dependent on the TRL motif of NpT2a. We conclude that appropriate trafficking of NpT2a to the plasma membrane is dependent on the initial association between NpT2a and NHERF1 through the COOH-terminal TRL motif of NpT2a in the ER/Golgi and requires redistribution of NHERF1 to the ER/Golgi.
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D. Murray R, D. Lederer E, J. Khundmiri S. Role of PTH in the Renal Handling of Phosphate. AIMS MEDICAL SCIENCE 2015. [DOI: 10.3934/medsci.2015.3.162] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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Fitzpatrick JM, Pellegrini M, Cushing PR, Mierke DF. Small molecule inhibition of the Na(+)/H(+) exchange regulatory factor 1 and parathyroid hormone 1 receptor interaction. Biochemistry 2014; 53:5916-22. [PMID: 25171053 PMCID: PMC4172209 DOI: 10.1021/bi500368k] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We have identified a series of small molecules that bind to the canonical peptide binding groove of the PDZ1 domain of NHERF1 and effectively compete with the association of the C-terminus of the parathyroid hormone 1 receptor (PTH1R). Employing nuclear magnetic resonance and molecular modeling, we characterize the mode of binding that involves the GYGF loop important for the association of the C-terminus of PTH1R. We demonstrate that the common core of the small molecules binds to the PDZ1 domain of NHERF1 and displaces a (15)N-labeled peptide corresponding to the C-terminus of PTH1R. The small size (molecular weight of 192) of this core scaffold makes it an excellent candidate for further elaboration in the development of an inhibitor for this important protein-protein interaction.
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Affiliation(s)
- Jeremy M Fitzpatrick
- Department of Chemistry and Department of Molecular and Cellular Biology, Dartmouth College , Hanover, New Hampshire 03755, United States
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Abstract
Fibrous dysplasia (FD) is a skeletal disorder caused by activating mutations in Gsα that result in elevations in cAMP. A feature of FD is elevated blood levels of the bone cell-derived phosphaturic hormone, fibroblast growth factor-23 (FGF23). FGF23 regulates serum phosphorus and active vitamin D levels by action on proximal renal tubule cells. An essential step in the production of biologically active FGF23 is glycosylation by the UDP-N-acetyl-α-D-galactosamine:polypeptide N-acetylgalactosaminyl transferase (ppGalNAc-T3). In the absence of glycosylation, FGF23 is processed into inactive N- and C-terminal proteins by a subtilisin proprotein convertase, probably furin. Normally, most if not all circulating FGF23 is intact. In FD, C-terminal levels are elevated, suggesting altered FGF23 processing. Altered processing in FD is the result of a cAMP-dependent, coordinated decrease in ppGalNAc-T3 and an increase in furin enzyme activity. These findings, and emerging data from other diseases, suggest regulation of FGF23 processing may be a physiologically important process.
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Affiliation(s)
- Alison M Boyce
- Bone Health Program, Division of Orthopaedics and Sports Medicine, Children’s National Medical Center, Washington, DC 20010
- Division of Endocrinology and Diabetes, Children’s National Medical Center, Washington, D.C. 20010
| | - Nisan Bhattacharyya
- Skeletal Clinical Studies Unit, Craniofacial and Skeletal Diseases Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, 20910
| | - Michael T Collins
- Skeletal Clinical Studies Unit, Craniofacial and Skeletal Diseases Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, 20910
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Shojaiefard M, Hosseinzadeh Z, Pakladok T, Bhavsar SK, Lang F. Stimulation of Na(+) coupled phosphate transporter NaPiIIa by janus kinase JAK2. Biochem Biophys Res Commun 2013; 431:186-91. [PMID: 23313484 DOI: 10.1016/j.bbrc.2012.12.137] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2012] [Accepted: 12/27/2012] [Indexed: 01/06/2023]
Abstract
BACKGROUND Na(+) coupled phosphate transporter NaPiIIa is the main carrier accomplishing phosphate transport across the apical cell membrane of proximal renal tubules and thus renal tubular phosphate reabsorption. The carrier is regulated by a wide variety of hormones and cellular signaling molecules. Hormones stimulating renal tubular phosphate transport and thus leading to hyperphosphatemia include growth hormone. Signaling of growth hormone involves activation of janus-activated kinase-2 JAK2, which has previously been shown to participate in the regulation of several Na(+) coupled transporters. Experiments exploring the effect of JAK2 on phosphate transport have, however, never been reported. The present study thus addressed the effect of JAK2 on NaPiIIa. METHODS cRNA encoding NaPiIIa was injected into Xenopus oocytes with or without additional injection of cRNA encoding wild type JAK2, the gain of function mutant JAK2(V617F) or inactive JAK2(K882E). Phosphate-induced current (I(NaPi)) reflecting electrogenic phosphate transport was determined by two electrode voltage clamp. Moreover, NaPiIIa protein abundance in the cell membrane was determined by chemiluminescence. RESULTS No appreciable I(NaPi) was observed in water injected oocytes or in oocytes expressing JAK2 alone. In NaPiIIa expressing oocytes I(NaPi) was significantly increased by additional expression of JAK2 or JAK2(V617F), but not by coexpression of JAK2(K882E). In oocytes expressing both, NaPiIIa and JAK2, I(NaPi) was gradually decreased by JAK2 inhibitor AG490 (40 μM). Coexpression of NaPiIIa and JAK2 or JAK2(V617F), but not of JAK2(K882E) increased NaPiIIa protein abundance in the cell membrane. Disruption of carrier protein insertion with Brefeldin A (5 μM) was followed by a decline of I(NaPi) to a similar extent in Xenopus oocytes expressing NaPiIIa with JAK2 and in Xenopus oocytes expressing NaPiIIa alone, suggesting that JAK2 did not affect carrier stability in the cell membrane. CONCLUSION JAK2 contributes to the regulation of phosphate transporter NaPiIIa.
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Affiliation(s)
- Manzar Shojaiefard
- Department of Physiology 1, University of Tübingen, Gmelinstr. 5, D-72076 Tübingen, Germany
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Wang B, Yang Y, Liu L, Blair HC, Friedman PA. NHERF1 regulation of PTH-dependent bimodal Pi transport in osteoblasts. Bone 2013; 52:268-77. [PMID: 23046970 PMCID: PMC3513631 DOI: 10.1016/j.bone.2012.10.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Revised: 09/18/2012] [Accepted: 10/01/2012] [Indexed: 02/01/2023]
Abstract
Control of systemic inorganic phosphate (Pi) levels is crucial for osteoid mineralization. Parathyroid hormone (PTH) mediates actions on phosphate homeostasis mostly by regulating the activity of the type 2 sodium-phosphate cotransporter (Npt2), and this action requires the PDZ protein NHERF1. Osteoblasts express Npt2 and in response to PTH enhance osteogenesis by increasing mineralized matrix. The regulation of Pi transport in osteoblasts is poorly understood. To address this gap we characterized PTH-dependent Pi transport and the role of NHERF1 in primary mouse calvarial osteoblasts. Under proliferating conditions osteoblasts express Npt2a, Npt2b, PTH receptor, and NHERF1. Npt2a mRNA expression was lower in calvarial osteoblasts from NHERF1-null mice. Under basal conditions Pi uptake in osteoblasts from wild-type mice was greater than that of knockout mice. PTH inhibited Pi uptake in proliferating osteoblasts from wild-type mice, but not in cells from knockout mice. In vitro induction of mineralization enhanced osteoblast differentiation and increased osterix and osteocalcin expression. Contrary to the results with proliferating osteoblasts, PTH increased Pi uptake and ATP secretion in differentiated osteoblasts from wild-type mice. PTH had no effect on Pi uptake or ATP release in differentiated osteoblasts from knockout mice. NHERF1 regulation of PTH-sensitive Pi uptake in proliferating osteoblasts is mediated by cAMP/PKA and PLC/PKC, while modulation of Pi uptake in differentiated osteoblasts depends only on cAMP/PKA signaling. The results suggest that NHERF1 cooperates with PTH in differentiated osteoblasts to increase matrix mineralization. We conclude that NHERF1 regulates PTH that differentially affects Na-dependent Pi transport at distinct stages of osteoblast proliferation and maturation.
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Affiliation(s)
- Bin Wang
- Laboratory for G Protein-Coupled Receptor Biology, Department of Pharmacology & Chemical Biology, Pittsburgh, PA, USA
| | - Yanmei Yang
- Laboratory for G Protein-Coupled Receptor Biology, Department of Pharmacology & Chemical Biology, Pittsburgh, PA, USA
| | - Li Liu
- Pittsburgh Veterans Affairs Medical Center and Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Harry C. Blair
- Pittsburgh Veterans Affairs Medical Center and Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Peter A. Friedman
- Laboratory for G Protein-Coupled Receptor Biology, Department of Pharmacology & Chemical Biology, Pittsburgh, PA, USA
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