The regulation of the overall renal tubular Pi transport by dietary, hormonal, or metabolic factors occurs via the proximal tubular apical brush border membrane (BBM) sodium gradient-dependent Pi (NaPi) cotransport proteins. Apical entry of Pi is mediated by coordinated actions of NaPi-2a, NaPi-2c, and PiT-2. Chronic alterations in dietary Pi, PTH, FGF23, Klotho, and other metabolic and dietary factors change the abundance of these transporters in BBM. There are however several important differences between these NaPi cotransporters the most important being that a) the time scale kinetics of the regulation of the NaPi transporters by dietary Pi and PTH are quite different, and b) there is also increasing evidence for the differential regulation of the NaPi transporters. This proposal will test the HYPOTHESES that NaPi-2a, NaPi-2c and PiT-2 are localized in distinct brush border membrane microdomains or nanodomains, resulting in: 1) differential regulation of lateral diffusion and clustering of the NaPi transporters in the brush border membrane;2) differential interactions with PDZ and ERM domain containing proteins, including NHERF-1, PDZK-1, and ezrin;3) differential rates of recruitment to endocytic pathways and/or differential mechanisms of endocytosis and internalization from the brush border membrane.
AIM 1 will determine if NaPi-2a, NaPi-2c and PiT-2 are localized in distinct BBM microdomains or nanodomains resulting in differential regulation of lateral diffusion and clustering of the NaPi transporters in the BBM in response to alterations in PTH, Pi, membrane lipid composition and actin dynamics.
AIM 2 will determine if NaPi-2a, NaPi-2c and PiT-2 have differential interactions with PDZ -ERM domain proteins, including NHERF-1, PDZK-1, and ezrin, which result in the differential internalization rate of the NaPi transporters in response to alterations in PTH, Pi and lipids.
AIM 3 will determine if NaPi-2a, NaPi-2c and PiT-2 have differential rates of recruitment to endocytic pathways and/or differential mechanisms of endocytosis and internalization from the brush border membrane in response to PTH, Pi and lipids.

Public Health Relevance

Disorders of Pi concentration are common clinical problems in aging, diabetes, cancer, chronic kidney disease, and AIDS by altering renal Pi absorption. Hyperphosphatemia results in vascular calcification and cardiac disease. Hypophosphatemia results in impaired energy production and bone mineralization. Genetic mutations of Pi transporters also cause bone disease, kidney stone formation, and kidney calcification.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
2R01DK066029-06
Application #
7917071
Study Section
Special Emphasis Panel (ZRG1-DKUS-F (02))
Program Officer
Rys-Sikora, Krystyna E
Project Start
2003-10-01
Project End
2014-05-31
Budget Start
2010-06-01
Budget End
2011-05-31
Support Year
6
Fiscal Year
2010
Total Cost
$501,379
Indirect Cost
Name
University of Colorado Denver
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
041096314
City
Aurora
State
CO
Country
United States
Zip Code
80045
Brenner, Michael D; Zhou, Ruobo; Conway, Daniel E et al. (2016) Spider Silk Peptide Is a Compact, Linear Nanospring Ideal for Intracellular Tension Sensing. Nano Lett 16:2096-102
Ranjit, Suman; Dvornikov, Alexander; Stakic, Milka et al. (2015) Imaging Fibrosis and Separating Collagens using Second Harmonic Generation and Phasor Approach to Fluorescence Lifetime Imaging. Sci Rep 5:13378
Fenton, Robert A; Murray, Fiona; Dominguez Rieg, Jessica A et al. (2014) Renal phosphate wasting in the absence of adenylyl cyclase 6. J Am Soc Nephrol 25:2822-34
Lanaspa, Miguel A; Caldas, Yupanqui A; Breusegem, Sophia Y et al. (2013) Inorganic phosphate modulates the expression of the NaPi-2a transporter in the trans-Golgi network and the interaction with PIST in the proximal tubule. Biomed Res Int 2013:513932
Hegan, Peter S; Giral, Hector; Levi, Moshe et al. (2012) Myosin VI is required for maintenance of brush border structure, composition, and membrane trafficking functions in the intestinal epithelial cell. Cytoskeleton (Hoboken) 69:235-51
Giral, Hector; Cranston, DeeAnn; Lanzano, Luca et al. (2012) NHE3 regulatory factor 1 (NHERF1) modulates intestinal sodium-dependent phosphate transporter (NaPi-2b) expression in apical microvilli. J Biol Chem 287:35047-56
Suhalim, Jeffrey L; Chung, Chao-Yu; Lilledahl, Magnus B et al. (2012) Characterization of cholesterol crystals in atherosclerotic plaques using stimulated Raman scattering and second-harmonic generation microscopy. Biophys J 102:1988-95
Lanzano, Luca; Gratton, Enrico (2012) Measurement of distance with the nanoscale precise imaging by rapid beam oscillation method. Microsc Res Tech 75:1253-64
Lanzano, Luca; Lei, Tim; Okamura, Kayo et al. (2011) Differential modulation of the molecular dynamics of the type IIa and IIc sodium phosphate cotransporters by parathyroid hormone. Am J Physiol Cell Physiol 301:C850-61
Lanzano, Luca; Digman, Michelle A; Fwu, Peter et al. (2011) Nanometer-scale imaging by the modulation tracking method. J Biophotonics 4:415-24

Showing the most recent 10 out of 33 publications