High-throughput Assessment of Mitochondrial Protein Synthesis in Mammalian Cells Using Mito-FUNCAT FACS

In addition to cytosolic protein synthesis, mitochondria also utilize another translation system that is tailored for mRNAs encoded in the mitochondrial genome. The importance of mitochondrial protein synthesis has been exemplified by the diverse diseases associated with in organello translation deficiencies. Various methods have been developed to monitor mitochondrial translation, such as the classic method of labeling newly synthesized proteins with radioisotopes and the more recent ribosome profiling. However, since these methods always assess the average cell population, measuring the mitochondrial translation capacity in individual cells has been challenging. To overcome this issue, we recently developed mito-fluorescent noncanonical amino acid tagging (FUNCAT) fluorescence-activated cell sorting (FACS), which labels nascent peptides generated by mitochondrial ribosomes with a methionine analog, L-homopropargylglycine (HPG), conjugates the peptides with fluorophores by an in situ click reaction, and detects the signal in individual cells by FACS equipment. With this methodology, the hidden heterogeneity of mitochondrial translation in cell populations can be addressed.

Automated summary

In addition to cytosolic protein synthesis, mitochondria also have a translation system tailored for mitochondrial genome-encoded mRNAs. The importance of mitochondrial protein synthesis is evidenced by the association with various diseases related to translation deficiencies in mitochondria. Although methods like labeling newly synthesized proteins and ribosome profiling have been used to monitor mitochondrial translation, measuring translation capacity in individual cells has been challenging. To address this issue, a method called mito-fluorescent noncanonical amino acid tagging (FUNCAT) fluorescence-activated cell sorting (FACS) has been developed recently, which allows the detection of mitochondrial translation in individual cells by labeling nascent peptides with a methionine analog and fluorophores.