Kinetic analysis of butyrate transport in human colon adenocarcinoma cells reveals two different carrier-mediated mechanisms
Résumé
Butyrate has anti-tumorigenic effects on colon cancer cells, inhibits cell growth and promotes differentiation and apoptosis. These effects depend on its intracellular concentration which is regulated by its transport. We have analyzed butyrate uptake kinetics in human colon adenocarcinoma cells sensitive to the apoptotic effects of butyrate (BCS-TC2, Caco-2 and HT29), in butyrate resistant cells (BCS-TC2.BR2), and in normal colonic cells (FHC). The properties of transport were analyzed with structural analogues, specific inhibitors, and different bicarbonate and sodium concentrations. Two carrier-mediated mechanisms were detected: a low-affinity/high-capacity (K m}=109±16 mM in BCS-TC2 cells) anion exchanger and a high-affinity/low-capacity (K m}=17.9±4.0 µM in BCS-TC2 cells) proton-monocarboxylate cotransporter that was energy-dependent and activated via PKCδ. All adenocarcinoma cells analyzed express MCT1, MCT4, ancillary protein CD147, and AE2. Silencing experiments show that MCT1, whose expression increases with butyrate-treatment in butyrate-sensitive cells, plays a key role in high-affinity transport. Low-affinity uptake was mediated by a butyrate-bicarbonate antiporter along with a possible contribution of AE2 and MCT4. Butyrate treatment increased uptake in a time- and dose-dependent manner in butyrate-sensitive but not in butyrate-resistant cells. The two butyrate-uptake activities in human colon adenocarcinoma cells enable butyrate transport at different physiological conditions to maintain cell functionality. The high-affinity/low-capacity transport functions under low butyrate concentrations and may be relevant for the survival of carcinoma cells in tumor regions with low glucose and butyrate availability as well as for the normal physiology of colonocytes.
Origine : Fichiers produits par l'(les) auteur(s)
Loading...