Conclusion
The sensitivity of cofilin to the inhibitor of deubiquitinating enzymes indicates the existence of a new non-catabolic mechanism of cofilin modification, which may be involved in the regulation of mitochondrial functions, specifically, the mitochondrial respiration and autophagy. The data help understand the molecular mechanisms of mitochondrial function in normal and pathological conditions, which may be useful in developing novel methods for the treatment of diseases of the nervous system.
Methods
The experiments were performed with C57BL/6 mice. To obtain cytoplasmic and mitochondrial fractions of the brain tissue, differential centrifugation was used. Expressions of cofilin, phospho-cofilin, K48- and K63-associated chains of ubiquitin, and the autophagy marker LC3B were determined using electrophoresis, immunoprecipitation and Western blot methods. To study the processes of ubiquitination, we used PR619 - the inhibitor of deubiquitinating enzymes. Respiratory activity of brain mitochondria was evaluated using high-resolution fluorespirometry.
Results
Modification of cofilin by non-canonical K63 multiubiquitin chains in the cytoplasm and mitochondria from murine brain was demonstrated. Different levels of phospho-cofilin, cofilin, and its ubiquitinated proteoforms were found. PR619, the inhibitor of deubiquitinating enzymes, affects the expression of phosphorylated and ubiquitinated forms of cofilin in the mitochondria and cytoplasm, at the same time it changes the activity of tissue respiration and mitophagy.