Mitochondrial ascorbic acid transport is mediated by a low-affinity form of the sodium-coupled ascorbic acid transporter-2

摘要: Despite the fundamental importance of redox metabolism mitochondria under normal and pathological conditions, our knowledge regarding transport vitamin C across mitochondrial membranes remains far from complete. We report here that human HEK-293 cells express a low-affinity ascorbic acid transporter molecularly corresponds to SVCT2, member sodium-coupled family 2. The SVCT1 is absent cells. Confocal colocalization experiments with anti-SVCT2 anti-organelle protein markers revealed most SVCT2 immunoreactivity was associated mitochondria, minor at endoplasmic reticulum very low plasma membrane. Immunoblotting proteins extracted highly purified fractions confirmed analysis sigmoidal concentration curve an apparent Km 0.6mM. Use siRNA for silencing expression produced major decrease in immunoreactivity, immunoblotting decreased by approximately 75%. Most importantly, accompanied concomitant rate. Further studies using overexpressing membrane altered kinetic properties are due ionic intracellular microenvironment (low sodium high potassium), potassium acting as concentration-dependent inhibitor SVCT2. discarded participation two glucose transporters previously described dehydroascorbic transporters; GLUT1 GLUT10 not expressed Overall, data indicate localized sensitive potassium, functions transporter. propose localization property shared cells, tissues, species.