ATP stimulates Na+-glucose cotransporter activity via cAMP and p38 MAPK in renal proximal tubule cells

Abstract

Extracellular ATP plays an important role in the regulation of renal function. However, the effect of ATP on the Na+-glucose cotransporters (SGLTs) has not been elucidated in proximal tubule cells (PTCs). Therefore, this study was performed to examine the action of ATP on SGLTs and their related signal pathways in primary cultured rabbit renal PTCs. ATP increased [14C]-α-methyl-d-glucopyranoside (α-MG) uptake in a time-dependent (>1 h) and dose-dependent (>10−6M) manner. ATP stimulated α-MG uptake by increasing in Vmaxwithout affecting Km. ATP-induced increase of α-MG uptake was correlated with the increase in both SGLT1 and SGLT2 protein expression levels. ATP-induced stimulation of α-MG uptake was blocked by suramin (nonspecific P2 receptor antagonist), RB-2 (P2Y receptor antagonist), and MRS-2179 (P2Y1receptor antagonist), suggesting a role for the P2Y receptor. ATP-induced stimulation of α-MG uptake was blocked by pertussis toxin (PTX, a Giprotein inhibitor), SQ-22536 (an adenylate cyclase inhibitor), and PKA inhibitor amide 14-22 (PKI). ATP also increased cAMP formation, which was blocked by PTX and RB-2. However, pretreatment of adenosine deaminase did not block ATP-induced cAMP formation. In addition, ATP-induced stimulation of α-MG uptake was blocked by SB-203580 (p38 MAPK inhibitor), but not by PD-98059 (p44/42 MAPK inhibitor) or SP-600125 (JNK inhibitor). Indeed, ATP induced phosphorylation of p38 MAPK. In conclusion, ATP increases α-MG uptake via cAMP and p38 MAPK in renal PTCs.