Biochem. J. (2008) 409
(311–320) (Printed in Great Britain)
Kinetic analysis of butyrate transport in human colon adenocarcinoma cells reveals two different carrier-mediated mechanisms
Emilio LECONA*, Nieves OLMO*, Javier TURNAY*, Angélica SANTIAGO-GÓMEZ*, Isabel LÓPEZ DE SILANES†, Myriam GOROSPE† and M. Antonia LIZARBE*1
*Department of Biochemistry and Molecular Biology I, Faculty of Chemistry, Complutense University, 28040 Madrid, Spain, and †Laboratory of Cellular and Molecular Biology, National Institute on Aging – Intramural Research Program, NIH (National Institutes of Health), Baltimore, MD 21224, U.S.A.
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 (Km=109±16 mM in BCS-TC2 cells) anion exchanger and a high-affinity/low-capacity (Km=17.9±4.0 μM in BCS-TC2 cells) proton–monocarboxylate co-transporter that was energy-dependent and activated via PKCδ (protein kinase Cδ). 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.
Key words: anion exchanger, butyrate uptake, colon adenocarcinoma, monocarboxylate transporter, protein kinase C (PKC) activator, small interfering RNA (siRNA).
Abbreviations used: AE, anion exchanger; BSM, bisindolylmaleimide I; 4-CHC, α-cyano-4-hydroxycinnamate; DIDS, 4,4′-di-isothiocyanostilbene-2,2′-disulfonate; HBSS, Hanks balanced salt solution; MCT, monocarboxylate transporter; PKC, protein kinase C; SCFA, short-chain fatty acid; siRNA, small interferring RNA; SLC4, solute carrier family; SLC4A2 etc.), SLC4 member 2 (etc.); RT, reverse transcriptase.
1To whom correspondence should be addressed (email lizarbe@bbm1.ucm.es).
Received 16 March 2007/30 July 2007; accepted 31 August 2007
Published as BJ Immediate Publication 31 August 2007, doi:10.1042/BJ20070374
© The Authors Journal compilation © 2008 Biochemical Society
Editorial Advisory Panel
RSS feeds
Table of contents by email
My BJ toolbox
