Thrombin is a novel regulator of hexokinase activity in mesangial cells

Background. Hexokinase (HK) activity is fundamentally important to cellular glucose uptake and metabolism. Phorbol esters increase both HK activity an d glucose utilization in cultured mesangial cells via a protein kinase C (P KC)- and extracellular signal-regulated kinases 1 and 2 (ERK1/2)-dependent mechanism. In adult kidneys, increased HK activity has been reported in bot h glomerular injury and in diabetes, but the mechanisms responsible for the se changes are unknown. Thrombin, a known activator of both PKC and ERK1/2, is increased in the settings of renal injury and diabetes. Thus, thrombin may contribute to the observed changes in HK activity in vivo. Methods. Thrombin and thrombin receptor agonists were tested for the abilit y to increase HK activity and glucose metabolism in murine mesangial (SV40 MES 13) cells. ERK1/2 activation was also evaluated in parallel. Thrombin i nhibition (hirudins), PKC depletion, Ser-Thr kinase inhibition (H-7), MEK1/ 2 inhibition (PD98059), pertussis toxin (PTX), and general inhibitors of tr anscription or translation were then tested for the ability to attenuate th ese effects. Results. Thrombin (greater than or equal to 0.01 U/mL) mimicked the effect of phorbol eaters, increasing HK activity >50% within 12 to 24 hours (P < 0 .05). This effect was inhibited by hirudins, mimicked by thrombin receptor agonists, and accompanied by increased Glc utilization. H-7, PD98059, and g eneral inhibitors of transcription or translation-but not PTX-prevented thr ombin-induced HK activity at 24 hours. PKC depletion and PD98059 also block ed the associated phosphorylation and activation of ERK1/2. Conclusions. Thrombin increases mesangial cell HK activity via a PTX-insens itive mechanism involving thrombin receptor activation, PKC-dependent activ ation of ERK1/2, and both ongoing gene transcription and de novo protein sy nthesis. As such, thrombin is a novel regulator of HK activity in mesangial cells and may play a role in coupling renal injury to metabolism.