Examination of Mitochondrial-Lysosomal Interactions in Riboflavin Transporter Deficiency

Riboflavin (vitamin B2) is integral to cellular processes and required for homeostasis. Riboflavin transporter deficiency (RTD) is a progressive neurodegenerative disorder resulting from mutations in SLC52A1, SLC52A2, or SLC52A3 genes. Symptoms of RDT include auditory neuropathy, muscle weakness, pontobulbar palsy, and respiratory compromise. These transporters, located in the plasma membrane, traffic Riboflavin into cells for application in the Electron Transport Chain. Mutations on these genes result in cellular stress and dysregulation of autophagic and mitophagic mechanisms. Mitochondria-lysosome interactions are essential for autophagic and mitophagic mechanisms, and defective mitochondria-lysosome interactions are often associated with neurodegenerative diseases. Despite this trend, the field had yet to investigate mitochondria-lysosome interactions in RTD. In order to learn about their typical intracellular behavior, mitochondria and lysosomes were analyzed together. Different environments of varying Riboflavin dosages were used to induce control and Riboflavin deficient conditions to examine mitochondrial and lysosomal inter-functionality. Results showed cell shrinkage, apoptosis, and subsequently reduced productions of mitochondria. The mitochondria present were also shown to be smaller and less prevalent in cell bodies, indicating interruptions in mitochondria-lysosome interactions