Epidermal growth factor inhibits 14C-alpha-methyl-D-glucopyranoside uptake in renal proximal tubule cells: involvement of PLC/PKC, p44/42 MAPK, and cPLA2.
The effect of EGF on (14)C-alpha-methyl-D-glucopyranoside (alpha-MG) uptake and its related signaling pathways were examined in primary cultured rabbit renal proximal tubule cells (PTCs). Epidermal growth factor (EGF) (50 ng/ml) was found to inhibit alpha-MG uptake, a distinctive proximal tubule marker. The EGF effect was blocked by AG1478 (an EGF receptor antagonist) or genistein and herbimycin (tyrosine kinase inhibitors), respectively. In addition, the EGF-induced inhibition of alpha-MG uptake was blocked by neomycin and U73122 (phospholipase C inhibitors) as well as staurosporine, H-7, and bisindolylmaleimide I (protein kinase C inhibitors). EGF was also observed to increase inositol phosphate formation. Furthermore, both the EGF-induced inhibition of alpha-MG uptake and increase of arachidonic acid (AA) release were blocked by AACOCF(3) (a cytosolic phospholipase A(2) inhibitor), indomethacin (a cyclooxygenase inhibitor), and econazole (a cytochrome P-450 epoxygenase inhibitor). We examined the involvement of mitogen-activated protein kinases (MAPKs) in mediating the effect of EGF on alpha-MG uptake. Indeed, EGF increased phosphorylation of p44/p42 MAPK and the EGF-induced inhibition of alpha-MG uptake as well as the stimulatory effect of EGF on AA release was blocked by PD 98059 (a p44/42 MAPK inhibitor), suggesting a causal relationship. However, inhibitors of PKC also prevented the EGF-induced increase of AA release. In conclusion, EGF partially inhibited alpha-MG uptake via PLC/PKC, p44/42 MAPK, and PLA(2) signaling pathways.
Jae Han
Ho
H
Department of Veterinary Physiology, College of Veterinary Medicine, Hormone Research Center, Chonnam National University, Gwangju, Korea. hjhan@chonnam.ac.kr
Yeong Park
Ji
J
Jung Lee
Yun
Y
Taub
Mary
M
D000818:Animals; D000941:Antigens / Q000378:metabolism; D015153:Blotting, Western; D002478:Cells, Cultured; D003598:Cytoskeletal Proteins / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D007687:Kidney Tubules, Proximal / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D008757:Methylglucosides / Q000378:metabolism*; D010741:Phospholipases A / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D011817:Rabbits; D015398:Signal Transduction / Q000502:physiology*
D000941:Antigens; D003598:Cytoskeletal Proteins; D004791:Enzyme Inhibitors; C065888:IFI44 protein, human; D008757:Methylglucosides; C027020:methylglucoside; D004815:Epidermal Growth Factor; D011493:Protein Kinase C; D010741:Phospholipases A