title: Phosphatidylinositol 3-kinase mediates inhibitory effect of angiotensin II on sodium/glucose cotransporter in renal epithelial cells.
abstract: Effects of angiotensin II (ANGII) on regulation of sodium/glucose cotransporter (SGLT1) activity were investigated in LLC-PK(1) cells, renal proximal epithelial cell line. ANGII inhibited alpha-[14C] methyl-D-glucopyranoside (AMG) uptake into LLC-PK(1) cells in a dose-dependent manner. This inhibition was based on a decrease in maximal transport rate (Vmax) of AMG from 2.20 nmol/mg protein/15 min to 1.19 nmol/mg protein/15 min, although apparent affinity constant (Km) did not alter. In western blot analysis, protein level of SGLT1 in brush border membrane (BBM) was decreased by ANGII, although total SGLT1 was not altered. In the aspect of intracellular signal transduction, ANGII blocked the formation of cAMP. Pertussis toxin, an inactivator of Gi protein that control intracellular cAMP level, completely prevented the decrease of AMG uptake caused by ANGII. 8-Br-cAMP, a cell membrane permeable cAMP analogue, increased AMG uptake and protein level of SGLT1 in BBM. Both wortmannin and LY294002 that are phosphatidylinositol (PI) 3-kinase inhibitors, inhibited the SGLT1 activity, and also attenuated the effect of 8-Br-cAMP on SGLT1 activity. Those inhibitors prevented the 8-Br-cAMP-induced expression of SGLT1 in plasma membrane. We conclude that ANGII plays an important role in post-translational regulation in SGLT1. Inhibition of SGLT1 translocation is suggested to be caused by inactivation of protein kinase A and decrease of PI 3-kinase activity.
authors.affiliation: Department of Environmental Biochemistry and Toxicology, University of Shizuoka School of Pharmaceutical Sciences, 52-1 Yada, Shizuoka city, Shizuoka 422-8526, Japan.
authors.forename: Kazuya
authors.initials: K
authors.lastname: Kawano
authors.forename: Akira
authors.initials: A
authors.lastname: Ikari
authors.forename: Mika
authors.initials: M
authors.lastname: Nakano
authors.forename: Yasunobu
authors.initials: Y
authors.lastname: Suketa
mesh_terms: D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000704:Analysis of Variance; D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D015153:Blotting, Western; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism*; D007668:Kidney / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D018374:LLC-PK1 Cells; D008562:Membrane Glycoproteins / Q000037:antagonists & inhibitors*; D008871:Microvilli / Q000187:drug effects / Q000378:metabolism; D009004:Monosaccharide Transport Proteins / Q000037:antagonists & inhibitors*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D051269:Sodium-Glucose Transporter 1; D013552:Swine
chemical_list: D008562:Membrane Glycoproteins; D009004:Monosaccharide Transport Proteins; D051269:Sodium-Glucose Transporter 1; D000804:Angiotensin II; D015124:8-Bromo Cyclic Adenosine Monophosphate; D019869:Phosphatidylinositol 3-Kinases