کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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1950987 | 1055730 | 2010 | 12 صفحه PDF | دانلود رایگان |

Chronic hyperglycaemia during diabetes leads to non-enzymatic glycation of proteins to form advanced glycation end products (AGEs) that contribute to nephropathy. In diabetes, renal Na+ K+ ATPase (NKA) activity is downregulated and phosphoinositide metabolism is upregulated. We examined the effects of AGEs on NKA activity in porcine LLC-PK1 and human HK2 proximal tubule epithelial cells. AGE-BSA increased cellular phosphoinositol 4,5 bisphosphate (PIP2) production as determined by immunofluorescence microscopy and thin layer chromatography. AGE-BSA (40 μM) induced 3H-arachidonic acid release and reactive oxygen species (ROS) production via cytosolic phospholipase A2(cPLA2) activation. Within minutes, AGE-BSA significantly inhibited NKA surface expression and activity in a dose- and time-dependent manner as determined by immunofluorescence staining and [86Rb+] uptake, respectively, suggesting AGEs inhibit NKA by stimulating its endocytosis. The AGE-BSA-induced decrease in cell surface NKA was reversed by a cPLA2α inhibitor, neomycin, a PIP2 inhibitor, and PP2, a Src inhibitor. AGE-BSA increased binding of NKA to the α-adaptin but not β2- or μ2-adaptin subunits of the AP-2 clathrin pit adaptor complex. Transfection of HK2 cells with PIP5Kγ siRNA prevented AGE-BSA inhibition of NKA activity. AGEs may stimulate PIP5Kγ to increase PIP2 production, which may enhance AP-2 localisation to clathrin pits, increase clathrin pit formation, enhance NKA cargo recognition by AP-2 and/or stimulate cPLA2α activity. These results suggest AGEs modulate arachidonic acid and phosphoinositide metabolism to inhibit NKA via clathrin-mediated endocytosis. Elucidation of new intracellular AGE signaling pathways may lead to improved therapies for diabetic nephropathy.
Journal: Biochimica et Biophysica Acta (BBA) - Molecular Cell Research - Volume 1803, Issue 8, August 2010, Pages 919–930