In:
Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 97, No. 14 ( 2000-07-05), p. 8157-8162
Abstract:
Transforming growth factor β (TGF-β) has been shown to participate in the pathophysiology of diabetic complications. As shown most recently, TGF-β stimulates the expression of a distinct serine/threonine kinase (hSGK) which had previously been cloned as an early gene transcriptionally regulated by cell volume alterations. The present study was performed to elucidate transcription and function of hSGK in diabetic nephropathy. As shown by Northern blotting, an increase of extracellular glucose concentration increased hSGK mRNA levels in cultured cells, an effect qualitatively mimicked by osmotic cell shrinkage or treatment with TGF-β (2 μg/liter), phorbol 12,13-didecanoate (1 μM), or the Ca 2+ ionophore ionomycin (1 μM) and blunted by high concentrations of nifedipine (10 and 100 μM). In situ hybridization revealed that hSGK transcription was markedly enhanced in diabetic nephropathy, with particularly high expression in mesangial cells, interstitial cells, and cells in thick ascending limbs of Henle's loop and distal tubules. According to voltage clamp and tracer flux studies in Xenopus oocytes expressing the renal epithelial Na + channel ENaC or the mouse thick ascending limb Na + ,K + ,2Cl − cotransporter BSC-1, coexpression with hSGK stimulated ENaC and BSC-1 11-fold and 6-fold, respectively, effects reversed by kinase inhibitors staurosporine (1 μM) and chelerythrine (1 μM) and not elicited by inactive hSGK. In conclusion, excessive extracellular glucose concentrations enhance hSGK transcription, which in turn stimulates renal tubular Na + transport. These observations disclose an additional element in the pathophysiology of diabetic nephropathy.
Type of Medium:
Online Resource
ISSN:
0027-8424
,
1091-6490
DOI:
10.1073/pnas.97.14.8157
Language:
English
Publisher:
Proceedings of the National Academy of Sciences
Publication Date:
2000
detail.hit.zdb_id:
209104-5
detail.hit.zdb_id:
1461794-8
SSG:
11
SSG:
12
