Overproduction of phosphoprotein enriched in diabetes (PED) induces mesangial expansion and upregulates protein kinase C-beta activity and TGF-beta1 expression.
OBJECTIVE
Overproduction of phosphoprotein enriched in diabetes (PED, also known as phosphoprotein enriched in astrocytes-15 [PEA-15]) is a common feature of type 2 diabetes and impairs insulin action in cultured cells and in mice. Nevertheless, the potential role of PED in diabetic complications is still unknown.


METHODS
We studied the effect of PED overproduction and depletion on kidney function in animal and cellular models.


RESULTS
Transgenic mice overexpressing PED (PEDTg) featured age-dependent increases of plasma creatinine levels and urinary volume, accompanied by expansion of the mesangial area, compared with wild-type littermates. Serum and kidney levels of TGF-beta1 were also higher in 6- and 9-month-old PEDTg. Overexpression of PED in human kidney 2 cells significantly increased TGF-beta1 levels, SMAD family members (SMAD)2/3 phosphorylation and fibronectin production. Opposite results were obtained following genetic silencing of PED in human kidney 2 cells by antisense oligonucleotides. Inhibition of phospholipase D and protein kinase C-beta by 2-butanol and LY373196 respectively reduced TGF-beta1, SMAD2/3 phosphorylation and fibronectin production. Moreover, inhibition of TGF-beta1 receptor activity and SMAD2/3 production by SB431542 and antisense oligonucleotides respectively reduced fibronectin secretion by about 50%. TGF-beta1 circulating levels were significantly reduced in Ped knockout mice and positively correlated with PED content in peripheral blood leucocytes of type 2 diabetic patients.


CONCLUSIONS
These data indicate that PED regulates fibronectin production via phospholipase D/protein kinase C-beta and TGF-beta1/SMAD pathways in kidney cells. Raised PED levels may therefore contribute to the abnormal accumulation of extracellular matrix and renal dysfunction in diabetes.
Department of Cellular and Molecular Biology and Pathology, Federico II University of Naples, Via Pansini 5, 80131, Naples, Italy.
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Oriente
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Iovino
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A
Cassese
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C
Romano
C
C
Miele
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G
Troncone
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M
Balletta
A
A
Perfetti
G
G
Santulli
G
G
Iaccarino
R
R
Valentino
F
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Beguinot
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Formisano
D000199:Actins / Q000235:genetics; D000818:Animals; D001253:Astrocytes / Q000378:metabolism; D001794:Blood Pressure; D017931:DNA Primers; D003922:Diabetes Mellitus, Type 1 / Q000150:complications / Q000235:genetics / Q000503:physiopathology; D003924:Diabetes Mellitus, Type 2 / Q000150:complications / Q000235:genetics / Q000503:physiopathology; D003928:Diabetic Nephropathies / Q000453:epidemiology; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005353:Fibronectins / Q000235:genetics; D005786:Gene Expression Regulation; D006339:Heart Rate; D006801:Humans; D007328:Insulin / Q000097:blood; D007668:Kidney / Q000502:physiology; D007676:Kidney Failure, Chronic / Q000209:etiology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D010641:Phenotype; D010750:Phosphoproteins / Q000096:biosynthesis / Q000235:genetics; D011493:Protein Kinase C / Q000235:genetics*; D064546:Protein Kinase C beta; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051899:Smad2 Protein / Q000235:genetics; D053773:Transforming Growth Factor beta1 / Q000235:genetics*; D015854:Up-Regulation
D000199:Actins; D017931:DNA Primers; D005230:Fatty Acids, Nonesterified; D005353:Fibronectins; D007328:Insulin; D010750:Phosphoproteins; C497782:SMAD2 protein, human; D051899:Smad2 Protein; D053773:Transforming Growth Factor beta1; D011493:Protein Kinase C; D064546:Protein Kinase C beta