Publications

• The loop between helix 4 and helix 5 in the monocarboxylate transporter MCT1 is important for substrate selection and protein stability.

  Galic S., Schneider H.P., Broeer A., Deitmer J.W., Broeer S.

  Transport of lactate, pyruvate and the ketone bodies acetoacetate and beta-hydroxybutyrate, is mediated in most mammalian cells by members of the monocarboxylate transporter family (SLC16). A conserved signature sequence has been identified in this family, which is located in the loop between heli ... >> More

  Transport of lactate, pyruvate and the ketone bodies acetoacetate and beta-hydroxybutyrate, is mediated in most mammalian cells by members of the monocarboxylate transporter family (SLC16). A conserved signature sequence has been identified in this family, which is located in the loop between helix 4 and helix 5 and extends into helix 5. We have mutated residues in this signature sequence in the rat monocarboxylate transporter (MCT1) to elucidate the significance of this region for monocarboxylate transport. Mutation of R143 and G153 resulted in complete inactivation of the transporter. For the MCT1(G153V) mutant this was explained by a failure to reach the plasma membrane. The lack of transport activity of MCT1(R143Q) could be partially rescued by the conservative exchange R143H. The resulting mutant transporter displayed reduced stability, a decreased V (max) of lactate transport but not of acetate transport, and an increased stereoselectivity. Mutation of K137, K141 and K142 indicated that only K142 played a significant role in the transport mechanism. Mutation of K142 to glutamine resulted in an increase of the K (m) for lactate from 5 mM to 12 mM. In contrast with MCT1(R143H), MCT1(K142Q) was less stereoselective than the wild-type. A mechanism is proposed that includes all critical residues. << Less

  Biochem. J. 376:413-422(2003) [PubMed] [EuropePMC]

• Participation of a proton-cotransporter, MCT1, in the intestinal transport of monocarboxylic acids.

  Tamai I., Takanaga H., Maeda H., Sai Y., Ogihara T., Higashida H., Tsuji A.

  A molecular mechanism for the intestinal monocarboxylic acid transport was characterized by using a proton/monocarboxylate transporter, MCT1, in Chinese hamster ovary (CHO) cells, first found by Garcia et al. (Cell, 76, 865-873, 1994). Northern blotting analysis showed that MCT1-isomers exist in t ... >> More

  A molecular mechanism for the intestinal monocarboxylic acid transport was characterized by using a proton/monocarboxylate transporter, MCT1, in Chinese hamster ovary (CHO) cells, first found by Garcia et al. (Cell, 76, 865-873, 1994). Northern blotting analysis showed that MCT1-isomers exist in the rat and rabbit intestinal enterocytes and Caco-2 cells. The expression of [14C]lactic acid uptake by Xenopus laevis oocytes injected with rabbit intestinal mRNA was reduced by hybridizing the mRNA with a MCT1 cDNA of CHO cells before microinjection used as the antisense DNA. [14C]Lactic acid uptake by CHO cells was pH dependent, saturable, stereospecific, and reduced in the presence of acetic acid, benzoic acid, S- and R-ibuprofen, S- and R-mandelic acid, nicotinic acid, pravastatin, propionic acid and valproic acid. In addition, several monocarboxylic acids were transported in pH-dependent and saturable manners. These results suggest that the intestinal MCT1-related protein contributes to a carrier-mediated absorption for organic weak acid compounds. << Less

  Biochem Biophys Res Commun 214:482-489(1995) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.

• Metabolism, compartmentation, transport and production of acetate in the cortical brain tissue slice.

  Rae C., Fekete A.D., Kashem M.A., Nasrallah F.A., Broer S.

  Acetate is a two carbon intermediate in metabolism. It is an accepted marker of astrocytic metabolism, and a substrate for production of metabolites such as glutamine, glutamate and GABA. However, anomalies exist in the current explanations of compartmentation and metabolism of acetate. Here, we i ... >> More

  Acetate is a two carbon intermediate in metabolism. It is an accepted marker of astrocytic metabolism, and a substrate for production of metabolites such as glutamine, glutamate and GABA. However, anomalies exist in the current explanations of compartmentation and metabolism of acetate. Here, we investigated these anomalies by examining transport, production and metabolism of acetate. Acetate is a good substrate for the neuronal monocarboxylate transporter MCT2 (K(M) = 2.58 ± 0.8) and the glial MCT1 but a poor substrate for the glial MCT4. Acetate is accumulated by brain cortical tissue slices to concentrations in excess of those in the media, suggesting active transport, possibly via the sodium dependent SMCT. [2-(13)C]Acetate is produced from [3-(13)C]pyruvate, [3-(13)C]lactate and [1-(13)C]glucose with the rate of production related to acetyl-CoA levels, which is likely generated in a ubiquitous cytosolic compartment via acetyl-CoA hydrolase. Citrate breakdown occurs in response to demand for acetyl-CoA units; this citrate is not derived from acetate carbon but its fate is influenced by acetate levels. Finally, use of acetate is altered by levels of nicotinamide or NAD(+). This suggests that metabolism of acetate is controlled rigorously at the enzyme level, via changes in the acetylation status of acetyl-CoA synthetase and is not regulated by restriction of uptake. << Less

  Neurochem Res 37:2541-2553(2012) [PubMed] [EuropePMC]

• Identity of a Plasmodium lactate/H(+) symporter structurally unrelated to human transporters.

  Wu B., Rambow J., Bock S., Holm-Bertelsen J., Wiechert M., Soares A.B., Spielmann T., Beitz E.

  Maintenance of a high glycolytic flow rate is critical for the rapid growth and virulence of malarial parasites. The parasites release two moles of lactic acid per mole of glucose as the anaerobic end product. However, the molecular identity of the Plasmodium lactate transporter is unknown. Here w ... >> More

  Maintenance of a high glycolytic flow rate is critical for the rapid growth and virulence of malarial parasites. The parasites release two moles of lactic acid per mole of glucose as the anaerobic end product. However, the molecular identity of the Plasmodium lactate transporter is unknown. Here we show that a member of the microbial formate-nitrite transporter family, PfFNT, acts as a lactate/proton symporter in Plasmodium falciparum. Besides L-lactate, PfFNT transports physiologically relevant D-lactate, as well as pyruvate, acetate and formate, and is inhibited by the antiplasmodial compounds phloretin, furosemide and cinnamate derivatives, but not by p-chloromercuribenzene sulfonate (pCMBS). Our data on PfFNT monocarboxylate transport are consistent with those obtained with living parasites. Moreover, PfFNT is the only transporter of the plasmodial glycolytic pathway for which structure information is available from crystals of homologous proteins, rendering it amenable to further evaluation as a novel antimalarial drug target. << Less

  Nat. Commun. 6:6284-6284(2015) [PubMed] [EuropePMC]

  This publication is cited by 4 other entries.