Monocarboxylate transporter 4 (MCT4) is a high affinity transporter capable of exporting lactate in high-lactate microenvironments

• Autor: Contreras-Baeza, Yasna ; Sandoval, Pamela Y. ; Alarcón, Romina ; Galaz, Alex ; Cortés-Molina, Francisca ; Alegría, Karin ; Baeza-Lehnert, Felipe ; Arce-Molina, Robinson ; Guequén, Anita ; Flores, Carlos A. ; San Martín, Alejandro ; Barros, L. Felipe
• Assuntos: Biological Transport - drug effects ; cancer ; Cell Line, Tumor ; CRISPR-Cas Systems - genetics ; Diclofenac - pharmacology ; Fluoresceins - chemistry ; Gene Editing ; HEK293 Cells ; Humans ; Hydrogen-Ion Concentration ; Kinetics ; Lactic Acid - metabolism ; macrophage ; Macrophages - cytology ; Macrophages - metabolism ; Metabolism ; Michaelis-Menten ; monocarboxylate transporter ; Monocarboxylic Acid Transporters - antagonists & inhibitors ; Monocarboxylic Acid Transporters - genetics ; Monocarboxylic Acid Transporters - metabolism ; Muscle Proteins - antagonists & inhibitors ; Muscle Proteins - genetics ; Muscle Proteins - metabolism ; Protein Isoforms - antagonists & inhibitors ; Protein Isoforms - genetics ; Protein Isoforms - metabolism ; pyruvate ; Pyruvic Acid - metabolism ; transporter
• É parte de: The Journal of biological chemistry, 2019-12, Vol.294 (52), p.20135-20147
• Notas: ObjectType-Article-1
  SourceType-Scholarly Journals-1
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  Edited by Mike Shipston
  
• Descrição: Monocarboxylate transporter 4 (MCT4) is an H+-coupled symporter highly expressed in metastatic tumors and at inflammatory sites undergoing hypoxia or the Warburg effect. At these sites, extracellular lactate contributes to malignancy and immune response evasion. Intriguingly, at 30–40 mm, the reported Km of MCT4 for lactate is more than 1 order of magnitude higher than physiological or even pathological lactate levels. MCT4 is not thought to transport pyruvate. Here we have characterized cell lactate and pyruvate dynamics using the FRET sensors Laconic and Pyronic. Dominant MCT4 permeability was demonstrated in various cell types by pharmacological means and by CRISPR/Cas9-mediated deletion. Respective Km values for lactate uptake were 1.7, 1.2, and 0.7 mm in MDA-MB-231 cells, macrophages, and HEK293 cells expressing recombinant MCT4. In MDA-MB-231 cells MCT4 exhibited a Km for pyruvate of 4.2 mm, as opposed to >150 mm reported previously. Parallel assays with the pH-sensitive dye 2′,7′-bis-(carboxyethyl)-5-(and-6)-carboxyfluorescein (BCECF) indicated that previous Km estimates based on substrate-induced acidification were severely biased by confounding pH-regulatory mechanisms. Numerical simulation using revised kinetic parameters revealed that MCT4, but not the related transporters MCT1 and MCT2, endows cells with the ability to export lactate in high-lactate microenvironments. In conclusion, MCT4 is a high-affinity lactate transporter with physiologically relevant affinity for pyruvate.
  
• Editor: United States: Elsevier Inc
  
• Idioma: Inglês