title: Kinetic analysis of butyrate transport in human colon adenocarcinoma cells reveals two different carrier-mediated mechanisms.
abstract: Butyrate has antitumorigenic 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 analysed butyrate uptake kinetics in human colon adenocarcinoma cells sensitive to the apoptotic effects of butyrate (BCS-TC2, Caco-2 and HT-29), in butyrate-resistant cells (BCS-TC2.BR2) and in normal colonic cells (FHC). The properties of transport were analysed 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 microM in BCS-TC2 cells) proton-monocarboxylate co-transporter that was energy-dependent and activated via PKCdelta (protein kinase Cdelta). All adenocarcinoma cells analysed express MCT (monocarboxylate transporter) 1, MCT4, ancillary protein CD147 and AE2 (anion exchanger 2). 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 tumour regions with low glucose and butyrate availability as well as for the normal physiology of colonocytes.
authors.affiliation: Department of Biochemistry and Molecular Biology I, Faculty of Chemistry, Complutense University, 28040 Madrid, Spain.
authors.forename: Emilio
authors.initials: E
authors.lastname: Lecona
authors.forename: Nieves
authors.initials: N
authors.lastname: Olmo
authors.forename: Javier
authors.initials: J
authors.lastname: Turnay
authors.forename: Angélica
authors.initials: A
authors.lastname: Santiago-Gómez
authors.forename: Isabel
authors.initials: I
authors.lastname: López de Silanes
authors.forename: Myriam
authors.initials: M
authors.lastname: Gorospe
authors.forename: M Antonia
authors.initials: MA
authors.lastname: Lizarbe
mesh_terms: D000230:Adenocarcinoma / Q000378:metabolism*; D027321:Anion Transport Proteins / Q000096:biosynthesis; D000838:Anions; D017920:Antiporters / Q000096:biosynthesis; D051926:Basigin / Q000096:biosynthesis; D001692:Biological Transport; D002087:Butyrates / Q000378:metabolism* / Q000493:pharmacokinetics; D018797:Cell Cycle Proteins / Q000096:biosynthesis; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000378:metabolism*; D017931:DNA Primers / Q000737:chemistry; D005947:Glucose / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D015513:Oncogene Proteins / Q000096:biosynthesis; D011493:Protein Kinase C / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D064606:SLC4A Proteins
chemical_list: D027321:Anion Transport Proteins; D000838:Anions; D017920:Antiporters; D002087:Butyrates; D018797:Cell Cycle Proteins; D017931:DNA Primers; C115081:MCTS1 protein, human; D015513:Oncogene Proteins; D034741:RNA, Small Interfering; D064606:SLC4A Proteins; D051926:Basigin; D011493:Protein Kinase C; D005947:Glucose