Arginine stimulates cdx2-transformed intestinal epithelial cell migration via a mechanism requiring both nitric oxide and phosphorylation of p70 S6 kinase

In intestinal cells, arginine (Arg) is 1 of the 2 most potent amino acid activators of p70(56k), a key regulator of 5'- terminal oligopyrimidine mRNA translation, a necessary condition for increased cell migration. To investigate the mechanism of response to Arg, we used the rat crypt cell line cdx2-transformed IEC-6 cells (cdx2-IEC) and measured cell migration, immunocytochemical analysis of p70(s6k) activation in response to Arg, and production of nitric oxide (NO). When treated with Arg, cdx2-IEC increased in phosphorylation on Thr-389 of p70(s6k) (pp70(s6k)) compared with control (P < 0.01). Phospho-Thr-421/Ser-424-p70(s6k) was located in the nucleus shortly after Arg treatment. Arg enhanced pp70(s6k), cell migration (55% wound coverage), and NO production. In comparison, the branched-chain amino acid leucine (Leu) activated pp70(s6k), was a weaker stimulator of migration (23% coverage), and did not increase NO. A total of 25 mu mol/L DETA-NONOate (DETA/NO) did not significantly enhance phosphorylation of p70(56k) but enhanced the rate of cell migration by similar to 25%. Wound coverage with Leu plus DETA/NO (25 mu mol/L) was greater than coverage with DETA/NO alone (P < 0.01). These and our previous studies lead to a rrodel in which Arg must stimulate both pp70(s6k) (in the nucleus) and NO release to enhance intestinal epithelial cell migration, which may be relevant to diseases that involve intestinal villous injury.