For the past several years, my lab has made key discoveries of the paracellular channel underlying renal calcium and magnesium handling. At the center of our story is a key tight junction protein complex from the kidney that comprises of three claudin proteins: claudin-14, claudin-16 and claudin-19. Human mutations in claudin-16 and claudin-19 cause the hereditary disease FHHNC (Familial Hypomagnesemia with Hypercalciuria and Nephrocalcinosis). Human SNPs in claudin-14 are associated with kidney stone diseases according to genome-wide association criteria. This proposal entitled Biochemical and biophysical nature of claudin-16 and claudin-19 channels will test the central hypothesis that the changes in paracellular permeabilities through claudin expression, function, interaction and combination underlie the key signaling functions of CaSR and PTH to regulate renal calcium and magnesium reabsorption. There are three aims in this proposal.
Aim 1 will elucidate the biochemical and biophysical basis of claudin-14, -16 and -19 functions in the kidney. We will use a range of biochemical and biophysical approaches with emphasis on a novel recording approach established by our lab based upon Scanning Ion Conductance Microscopy (SICM). SICM has, for the first time, allowed us to reveal paracellular permeabilities at submicron resolution.
Aim 2 will elucidate the regulatory basis for claudin in response to CaSR and PTH signaling. We will generate two key mouse models - TALH specific CaSR or PTH1R KO mice to decipher the CaSR and PTH specific regulation of claudins. We will also study how CaSR and PTH signaling cross talk in the kidney using double CaSR/PTH1R KO or a well-established pharmacological approach.
Aim 3 will determine the mechanistic role of claudin in renal calcium handling. The renal transport function of claudin monomer or oligomer will be determined using combinatorial knockout approaches based upon the claudin KO mouse models we have established - claudin-14, -16, -19 single, double and triple KO and claudin- 14 overexpression mice. We will also study how PTH, CaSR and microRNA alter paracellular permeabilities based upon changes in claudin expression, function, interaction, and combination using single nephron perfusion techniques.

Public Health Relevance

: Kidneys function by initially excreting many salts and small molecules found in the blood, then selectively taking back those that need to be conserved while allowing others to be excreted in the urine. This grant will study claudin functions of cell-cell junctions that provide one of the key pathways (the paracellular pathway) used by the kidney to move salt between urine and blood. Defects in claudin function result in a broad range of renal diseases, including hypomagnesemia, hypercalciuria, nephrocalcinosis and kidney stone.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK084059-08
Application #
9270016
Study Section
Kidney Molecular Biology and Genitourinary Organ Development (KMBD)
Program Officer
Ketchum, Christian J
Project Start
2010-04-01
Project End
2019-04-30
Budget Start
2017-05-01
Budget End
2018-04-30
Support Year
8
Fiscal Year
2017
Total Cost
Indirect Cost
Name
Washington University
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
068552207
City
Saint Louis
State
MO
Country
United States
Zip Code
63130
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