Insulin actions are intertwined with nutrient uptake in many tissues. Insulin sensitivity occurs, also, in enterocytes, through both apical and basolateral receptors. On GI epithelial apical membranes, insulin is able to stimulate expression of the oligopeptide transporter SLC15A1/PEPT1 which is a prototypical marker at the same time of the enterocyte-like differentiation and of the insulin-dependent effects on uptake dynamics and enterocyte maturation rearrangements. However, insulin effects on PEPT1 and GI are poorly investigated. Here, we evaluate the action of insulin on the expression of PEPT1 and on the SLC15A4/PHT1 endosomal counterpart, in Caco-2 intestinal cell monolayers at two different stages of spontaneous differentiation i.e. pre-differentiated (14 dps, days post seeding) and differentiated enterocyte-like cells (21 dps). We found differential regulation by insulin of the PEPT1 gene products depending on the differentiation stage, i.e. significant down-regulation in pre-differentiated monolayers vs. stabilized expression in differentiated monolayers. Regarding PHT1, its gene products were found up-regulated in differentiated cells, with insulin not exerting expression variations both in pre-differentiated both in enterocyte-like cells. But, remarkably, in the pre-differentiated insulin-treated monolayers we found that PHT1 expression levels are mainly due to an unproductive mRNA splice variant which in turn is not induced by insulin, totally, in mature monolayers. Overall, results suggest a coupled, splicing-mediated regulation of SLC15A1/PEPT1 and SLC15A4/PHT1 depending on insulin and differentiation stage, hinting a dual marker system for sensing the route of peptide absorption/turn-over and on-target/off-target effects of insulin on enterocytes. Key words: (3) enterocyte monolayer, insulin, SLC15 oligopeptide transporters.
Revealing regulation patterns of the coupled apical SLC(15)A(1)/PEPT1 and endosomal SLC(15)A(4)/PHT1 oligopeptide transport systems in enterocyte-like cell monolayers under insulin stimulation
Barca, A;Mazzei, A;Del Vecchio, G;Verri, T
2019-01-01
Abstract
Insulin actions are intertwined with nutrient uptake in many tissues. Insulin sensitivity occurs, also, in enterocytes, through both apical and basolateral receptors. On GI epithelial apical membranes, insulin is able to stimulate expression of the oligopeptide transporter SLC15A1/PEPT1 which is a prototypical marker at the same time of the enterocyte-like differentiation and of the insulin-dependent effects on uptake dynamics and enterocyte maturation rearrangements. However, insulin effects on PEPT1 and GI are poorly investigated. Here, we evaluate the action of insulin on the expression of PEPT1 and on the SLC15A4/PHT1 endosomal counterpart, in Caco-2 intestinal cell monolayers at two different stages of spontaneous differentiation i.e. pre-differentiated (14 dps, days post seeding) and differentiated enterocyte-like cells (21 dps). We found differential regulation by insulin of the PEPT1 gene products depending on the differentiation stage, i.e. significant down-regulation in pre-differentiated monolayers vs. stabilized expression in differentiated monolayers. Regarding PHT1, its gene products were found up-regulated in differentiated cells, with insulin not exerting expression variations both in pre-differentiated both in enterocyte-like cells. But, remarkably, in the pre-differentiated insulin-treated monolayers we found that PHT1 expression levels are mainly due to an unproductive mRNA splice variant which in turn is not induced by insulin, totally, in mature monolayers. Overall, results suggest a coupled, splicing-mediated regulation of SLC15A1/PEPT1 and SLC15A4/PHT1 depending on insulin and differentiation stage, hinting a dual marker system for sensing the route of peptide absorption/turn-over and on-target/off-target effects of insulin on enterocytes. Key words: (3) enterocyte monolayer, insulin, SLC15 oligopeptide transporters.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
