Fig. 8.

First images assessing co-localization of the monocarboxylate (lactate, pyruvate, β-hydroxybutyrate) transporter (MCT1) and mitochondrial the pyruvate carrier (mPC) in L6 cells, which shows the localization of DAPI-positive nuclei (A), MCT1 (B), mPC1 (C), and Mito Tracker-positive MR (D) in L6 cells. The merged images are shown in E. Co-localization analysis of mPC1 (C) and mitochondria (D) showed a Pearson correlation coefficient (r²) value of 0.8. Co-localization analysis of MCT1 (B) and mPC1 (C) showed an r² of 0.3, largely because MCT1 occupies sarcolemmal, mitochondrial, and peroxisomal compartments. A channel to represent the co-localization of MCT1 and mitochondria was created to image mMCT1; subsequent co-localization of mMCT1 with mPC1 resulted in an r² of 0.8 (F). White dots indicate the co-localization of mMCT1 and mPC1 as observed in Image J software. Whole images were contrast enhanced in A, B, C, D, and E. Similar results were observed for mPC2. Scale bar = 20 μm. It appears that both MCT1 and the putative mPC are co-localized to the mitochondria (r² = 0.8). However, at the light microscopic level, it is impossible to know if the 2 proteins interact physically and functionally. Also, with benefit of the Orbitrap liquid chromatography/mass spectrometry device, we would be able to determine fractional synthesis rates of mitochondrial lactate oxidation complex and mPC proteins.