Abstract
The present study was conducted to determine whether and how store-operated Ca(2+) entry (SOCE) in glomerular mesangial cells (MCs) was altered by high glucose (HG) and diabetes. Human MCs were treated with either normal glucose or HG for different time periods. Cyclopiazonic acid-induced SOCE was significantly greater in the MCs with 7-day HG treatment and the response was completely abolished by GSK-7975A, a selective inhibitor of store-operated Ca(2+) channels. Similarly, the inositol 1,4,5-trisphosphate-induced store-operated Ca(2+) currents were significantly enhanced in the MCs treated with HG for 7 days, and the enhanced response was abolished by both GSK-7975A and La(3+). In contrast, receptor-operated Ca(2+) entry in MCs was significantly reduced by HG treatment. Western blotting showed that HG increased the expression levels of STIM1 and Orai1 in cultured MCs. A significant HG effect occurred at a concentration as low as 10 mM, but required a minimum of 7 days. The HG effect in cultured MCs was recapitulated in renal glomeruli/cortex of both type I and II diabetic rats. Furthermore, quantitative real-time RT-PCR revealed that a 6-day HG treatment significantly increased the mRNA expression level of STIM1. However, the expressions of STIM2 and Orai1 transcripts were not affected by HG. Taken together, these results suggest that HG/diabetes enhanced SOCE in MCs by increasing STIM1/Orai1 protein expressions. HG upregulates STIM1 by promoting its transcription but increases Orai1 protein through a posttranscriptional mechanism.
Keywords:
Orai1; STIM1; diabetic nephropathy; high glucose; mesangial cells; store-operated Ca2+ entry.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Calcium Channel Agonists / pharmacology
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Calcium Channel Blockers / pharmacology
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Calcium Channels / drug effects
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Calcium Channels / genetics
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Calcium Channels / metabolism*
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Calcium Signaling* / drug effects
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Cells, Cultured
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Diabetes Mellitus, Experimental / complications
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Diabetes Mellitus, Experimental / genetics
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Diabetes Mellitus, Experimental / metabolism
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Diabetes Mellitus, Type 1 / complications
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Diabetes Mellitus, Type 1 / genetics
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Diabetes Mellitus, Type 1 / metabolism
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Diabetes Mellitus, Type 2 / complications
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Diabetes Mellitus, Type 2 / genetics
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Diabetes Mellitus, Type 2 / metabolism
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Diabetic Nephropathies / etiology
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Diabetic Nephropathies / genetics
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Diabetic Nephropathies / metabolism*
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Glucose / metabolism*
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Humans
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Inositol 1,4,5-Trisphosphate / metabolism
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Ion Channel Gating* / drug effects
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Male
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Membrane Glycoproteins / genetics
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Membrane Glycoproteins / metabolism
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Membrane Proteins / genetics
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Membrane Proteins / metabolism
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Mesangial Cells / drug effects
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Mesangial Cells / metabolism*
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Neoplasm Proteins / genetics
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Neoplasm Proteins / metabolism
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ORAI1 Protein
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RNA Processing, Post-Transcriptional
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RNA, Messenger / metabolism
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Rats
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Rats, Sprague-Dawley
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Stromal Interaction Molecule 1
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Time Factors
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Transcriptional Activation
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Up-Regulation
Substances
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Calcium Channel Agonists
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Calcium Channel Blockers
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Calcium Channels
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Membrane Glycoproteins
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Membrane Proteins
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Neoplasm Proteins
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ORAI1 Protein
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ORAI1 protein, human
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Orai1 protein, rat
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RNA, Messenger
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STIM1 protein, human
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Stim1 protein, rat
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Stromal Interaction Molecule 1
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Inositol 1,4,5-Trisphosphate
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Glucose