Metabolic acidosis is a common but potentially life-threatening disorder that occurs when too much acid accumulates in the blood. The kidney is the organ that is primarily concerned with controlling the level of acid in the blood. The cortical collecting duct (CCD) is a key segment of kidney tubule that adapts to the level of acid and pumps it out of the body. The long term goal is to determine how intercalated cells of the CCD adapt to acid-base disturbances by changing their transport of acid and bicarbonate. Rabbit CCDs, which normally secrete bicarbonate, exposed to 3h incubation at pH 6.8 secrete acid. The novel protein hensin is expressed in the extracellular matrix (ECM) surrounding adapting B-intercalated cells (ICs).
Aim 1 examines how Cyclosporin A (CsA) causes a distal renal tubular acidosis by preventing adaptation of B-ICs. CsA inhibits hensin pofymerization via an inhibition of the proline cis/trans isomerase activity of cyclophilin. Studies using specific inhibitors of these functions are performed in cultured ICs and CCDs incubated at pH 6.8 x 3 h to simulate acidosis. A """"""""knockdown"""""""" of cyclophilin will determine which cyclophilin is important in polymerizing hensin in cultured ICs and whether a defect in this cyclophilin causes acidosis.
Aim 2 examines the role of galectin-3 in hensin polymerization. Galectin-3 can help polymerize hensin in vitro.
This aim will determine which cells express galectin-3 and whether there is stimulation during acidosis.
The aim will determine if galectin-3 associates with hensin in the ECM in the adapting CCD and whether a dominant negative galectin-3 prevents hensin polymerization and adaptation of B-ICs in CCD.
This aim will establish whether expressed cyclophilin and galectin-3 can cooperate in the in vitro polymerization of hensin.
Aim 3 determines which integrins are expressed in ICs and which interact with hensin.
Aim 4 examines the role of hensin polymerization in the adaptation of CCD ICs to metabolic alkalosis, with the hypothesis that alkalosis reduces hensin polymerization by degrading hensin and allowing B-ICs to secrete bicarbonate to correct the abnormality. These studies should show how hensin and associated proteins mediate the kidney's adaptation to acid-base disturbances.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK050603-30
Application #
7751813
Study Section
Cellular and Molecular Biology of the Kidney Study Section (CMBK)
Program Officer
Ketchum, Christian J
Project Start
1990-07-01
Project End
2010-12-31
Budget Start
2010-01-01
Budget End
2010-12-31
Support Year
30
Fiscal Year
2010
Total Cost
$348,618
Indirect Cost
Name
University of Rochester
Department
Pediatrics
Type
Schools of Dentistry
DUNS #
041294109
City
Rochester
State
NY
Country
United States
Zip Code
14627
Schwartz, George J; Gao, XiaoBo; Tsuruoka, Shuichi et al. (2015) SDF1 induction by acidosis from principal cells regulates intercalated cell subtype distribution. J Clin Invest 125:4365-74
Purkerson, Jeffrey M; Schwaderer, Andrew L; Nakamori, Aya et al. (2015) Distinct ?-intercalated cell morphology and its modification by acidosis define regions of the collecting duct. Am J Physiol Renal Physiol 309:F464-73
Purkerson, Jeffrey M; Heintz, Eric V; Nakamori, Aya et al. (2014) Insights into acidosis-induced regulation of SLC26A4 (pendrin) and SLC4A9 (AE4) transporters using three-dimensional morphometric analysis of ?-intercalated cells. Am J Physiol Renal Physiol 307:F601-11
Hains, David S; Chen, Xi; Saxena, Vijay et al. (2014) Carbonic anhydrase 2 deficiency leads to increased pyelonephritis susceptibility. Am J Physiol Renal Physiol 307:F869-80
Chambrey, Regine; Kurth, Ingo; Peti-Peterdi, Janos et al. (2013) Renal intercalated cells are rather energized by a proton than a sodium pump. Proc Natl Acad Sci U S A 110:7928-33
Vijayakumar, Soundarapandian; Peng, Hu; Schwartz, George J (2013) Galectin-3 mediates oligomerization of secreted hensin using its carbohydrate-recognition domain. Am J Physiol Renal Physiol 305:F90-9
Purkerson, Jeffrey M; Tsuruoka, Shuichi; Suter, D Zachary et al. (2010) Adaptation to metabolic acidosis and its recovery are associated with changes in anion exchanger distribution and expression in the cortical collecting duct. Kidney Int 78:993-1005
Peng, Hu; Vijayakumar, Soundarapandian; Schiene-Fischer, Cordelia et al. (2009) Secreted cyclophilin A, a peptidylprolyl cis-trans isomerase, mediates matrix assembly of hensin, a protein implicated in epithelial differentiation. J Biol Chem 284:6465-75
Purkerson, J M; Kittelberger, A M; Schwartz, G J (2007) Basolateral carbonic anhydrase IV in the proximal tubule is a glycosylphosphatidylinositol-anchored protein. Kidney Int 71:407-16
Purkerson, J M; Schwartz, G J (2007) The role of carbonic anhydrases in renal physiology. Kidney Int 71:103-15

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