The plasma membrane (PM) is an important lipoproteic structure that separates the cytosol from the extracellular environment. This important structure has several functions, most of them performed by proteins at the PM, such as receptors, transporters and channels. The trafficking of these proteins is regulated under different stimuli from the extracellular environment, by two distinct pathways: the exocytic and the endocytic pathways.
The expression of monocarboxylate transporters (MCTs) at the PM is particularly relevant for the malignant phenotype of cancer cells. Cancer cells present the “Warburg effect”, which is characterized by an increased glucose consumption and lactic acid production, even in the presence of oxygen. Lactate is then exported by a proton symport mechanism, via MCTs, leading to extracellular acidification and tumor progression. MCTs are upregulated in cancer cells and their activity is regulated according to the oxygen availability, lactate concentration and expression of the MCT sub-type at the PM.
The aim of this study was to study the intracellular trafficking of MCTs, namely of MCT1 isoform. For this purpose, we used three distinct cell lines from breast cancer: MDA-MB-231, ZR-75–1 and SK-BR-3, which present different expression of MCT1at PM. These cell lines were all transfected with pEGFP-N1_MCT1 construct and the traffic of the protein was analysed at different times, namely at 24h, 48h and 72h, through GFP fluorescence. MCT1 was expressed in three cell lines and different locations were detected. In MDA-MB-231 cell line, the MCT1-GFP was located mainly in the nucleus membrane, while ZR-75–1 presented the MCT1-GFP at the PM and SK-BR-3 in the cytosol. According to the analysis of the results, we are currently studying elements and stimulus that regulate the trafficking of MCT1at the PM, what can open new perspectives for subsequent therapies.
