An agonist of a zinc-sensing receptor GPR39 enhances tight junction assembly in intestinal epithelial cells via an AMPK-dependent mechanism

Abstract

Intestinal barrier function depends on integrity of tight junctions, which serve as barriers to transepithelial influx of noxious substances/microorganisms from gut lumen. The G-protein coupled receptor 39 (GPR39) is a zinc-sensing receptor, which is expressed in several cell types including intestinal epithelial cells (IECs). The main objective of this study was to investigate the effect of GPR39 activation on tight junction assembly in IECs. Treatment with TC-G 1008 (1 μM -10 μM), a GPR39 agonist, and zinc (10 μM -100 μM) increased tight junction assembly in T84 cells. This effect was suppressed by pretreatment with compound C, an inhibitor of AMP-activated protein kinase (AMPK). In addition, western blot analysis revealed that treatment with TC-G 1008 induced AMPK activation in time- and concentration-dependent manners. Interestingly, inhibitors of phospholipase C (PLC) and calcium/calmodulin-dependent protein kinase kinase β (CaMKKβ) abrogated the effect of TC-G 1008 on inducing AMPK activation, tight junction assembly and zonula occludens-1 re-organization. Collectively, this study reveals a novel role of GPR39 in enhancing tight junction assembly in IECs via PLC-CaMKKβ-AMPK pathways. GPR39 agonists may be beneficial in the treatment of diseases associated impaired intestinal barrier function.