Abstract
Impaired albumin reabsorption by proximal tubular epithelial cells (PTECs) has been highlighted in diabetic nephropathy (DN), but little is known about the underlying molecular mechanisms. Here we find that ORAI1-3, are preferentially expressed in PTECs and downregulated in patients with DN. Hyperglycemia or blockade of insulin signaling reduces the expression of ORAI1-3. Inhibition of ORAI channels by BTP2 and diethylstilbestrol or silencing of ORAI expression impairs albumin uptake. Transgenic mice expressing a dominant-negative Orai1 mutant (E108Q) increases albuminuria, and in vivo injection of BTP2 exacerbates albuminuria in streptozotocin-induced and Akita diabetic mice. The albumin endocytosis is Ca2+-dependent and accompanied by ORAI1 internalization. Amnionless (AMN) associates with ORAIs and forms STIM/ORAI/AMN complexes after Ca2+ store depletion. STIM1/ORAI1 colocalizes with clathrin, but not with caveolin, at the apical membrane of PTECs, which determines clathrin-mediated endocytosis. These findings provide insights into the mechanisms of protein reabsorption and potential targets for treating diabetic proteinuria.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, N.I.H., Intramural
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Research Support, Non-U.S. Gov't
MeSH terms
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Albumins / drug effects
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Albumins / metabolism*
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Albuminuria / genetics*
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Albuminuria / metabolism
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Anilides / pharmacology
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Animals
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Calcium / metabolism
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Calcium Channel Blockers
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Calcium Channels / genetics*
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Calcium Channels / metabolism
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Case-Control Studies
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Caveolins / metabolism
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Cell Line
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Clathrin / metabolism
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Diabetes Mellitus, Experimental / metabolism*
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Diabetes Mellitus, Type 1 / metabolism*
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Diabetic Nephropathies / metabolism*
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Diethylstilbestrol / pharmacology
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Down-Regulation
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Endocytosis
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Epithelial Cells / drug effects
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Epithelial Cells / metabolism*
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Estrogens, Non-Steroidal / pharmacology
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Female
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Humans
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Hyperglycemia / genetics
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Hyperglycemia / metabolism
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Kidney / metabolism
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Kidney Tubules, Proximal / cytology
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Kidney Tubules, Proximal / drug effects
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Kidney Tubules, Proximal / metabolism*
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Male
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Membrane Proteins / metabolism
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Mice
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Mice, Transgenic
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Middle Aged
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Mutation
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ORAI1 Protein / antagonists & inhibitors
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ORAI1 Protein / genetics*
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ORAI1 Protein / metabolism
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ORAI2 Protein / antagonists & inhibitors
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ORAI2 Protein / genetics*
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ORAI2 Protein / metabolism
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Renal Reabsorption / drug effects
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Renal Reabsorption / genetics
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Stromal Interaction Molecule 1 / metabolism
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Thiadiazoles / pharmacology
Substances
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4-methyl-4'-(3,5-bis(trifluoromethyl)-1H-pyrazol-1-yl)-1,2,3-thiadiazole-5-carboxanilide
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Albumins
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Amn protein, mouse
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Anilides
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Calcium Channel Blockers
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Calcium Channels
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Caveolins
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Clathrin
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Estrogens, Non-Steroidal
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Membrane Proteins
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ORAI1 Protein
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ORAI1 protein, human
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ORAI2 Protein
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ORAI2 protein, human
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Orai1 protein, mouse
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Orai2 protein, mouse
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Orai3 protein, human
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Orai3 protein, mouse
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Stim1 protein, mouse
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Stromal Interaction Molecule 1
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Thiadiazoles
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Diethylstilbestrol
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Calcium