The mTOR-RUNX1 pathway regulates DC-SIGN expression in renal tubular epithelial cells

Abstract

Renal tubular epithelial cells (RTECs) play pivotal roles in the innate immune response in kidneys. Dendritic cell specific intracellular adhesion molecule–3 grabbing nonintegrin (DC-SIGN) functions as both the innate immune recognition receptor and the adhesion molecule. In our previous study, we found that DC-SIGN expression was induced in RTECs during renal inflammation. However, the underlying mechanism remains unclear. Here, we used the human renal proximal tubular epithelial cell lines (HK-2) to investigate the mechanism of TNF-α-induced expression of DC-SIGN. Our results showed that TNF-α up-regulated the expressions of DC-SIGN and Runt-related transcription factor 1 (RUNX1) in a time-dependent manner and that it up-regulated DC-SIGN promoter-driven luciferase activity in a dose-dependent manner. The mTOR inhibitor rapamycin and mTOR siRNA blocked the TNF-α-induced up-regulation of DC-SIGN expression. Meanwhile, DC-SIGN expression was also inhibited by RUNX1 siRNA and its inhibitor Ro5-3335. In addition, both mTOR and RUNX1 inhibitors attenuated TNF-α-induced the increase in DC-SIGN promoter-driven luciferase activity. Finally, we found that HK-2 cells exposed to rapamycin or mTOR siRNA reduced the TNF-α-induced up-regulation of RUNX1. In conclusion, these results indicated that the mTOR-RUNX1 pathway participates in the regulation of TNF-α-induced DC-SIGN expression in RTECs.