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.sup.s6k], 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.sup.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.sup.s6k] ([pp70.sup.s6k]) compared with control (P < 0.01). Phospho-Thr-421/Ser-424-[p70.sup.s6k] was located in the nucleus shortly after Arg treatment. Arg enhanced [pp70.sup.s6k], cell migration (55% wound coverage), and NO production. In comparison, the branched-chain amino acid leucine (Leu) activated [pp70.sup.s6k], was a weaker stimulator of migration (23% coverage), and did not increase NO. A total of 25 [micro]mol/L DETA-NONOate (DETA/NO) did not significantly enhance phosphorylation of [p70.sup.s6k] but enhanced the rate of cell migration by ~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 model in which Arg must stimulate both [pp70.sup.s6k] (in the nucleus) and NO release to enhance intestinal epithelial cell migration, which may be relevant to diseases that involve intestinal villous injury.