Alterations of the skeletal muscle nuclear proteome after acute exercise reveals a post-transcriptional influence.

Exercise is firmly established as a key contributor to overall well-being and is frequently employed as a therapeutic approach to mitigate various health conditions. One pivotal aspect of the impact of exercise lies in the systemic transcriptional response, which underpins its beneficial adaptations. Although extensive research has been devoted to understanding the transcriptional response to exercise, our knowledge of the protein constituents of nuclear processes accompanying gene expression in skeletal muscle remains largely elusive. We hypothesize that alterations in the nuclear proteome following exercise hold vital clues for comprehending exercise-induced transcriptional regulation and related nuclear functions. We first detail the successful isolation of skeletal muscle nuclei from C57BL/6 mice, encapsulating 2,030 proteins linked to nuclear processes such as transcription, RNA processing, chromatin modifications, and nuclear transport. We then used this approach to isolate muscle nuclei in sedentary, immediately post-, 1-h, and 4-h after a 30-min treadmill running session, to gain insight into the nuclear proteome after exercise. We found 54 proteins linked to mRNA splicing and nucleocytoplasmic transport, many of which were substantially reduced immediately postexercise followed by a rapid increase 1- and 4-h postexercise. Super-resolution microscopy experiments highlight localization changes in mRNA processing proteins postexercise, further suggesting changes in nuclear transport dynamics. Our data provide important insight into changes in the nuclear proteome following exercise. In particular, it highlights proteins contributing to mRNA processing and splicing in addition to transcriptional processes, with exercise offering broader changes in mechanisms modulating the molecular response to acute exercise.<b>NEW & NOTEWORTHY</b> Exercise plays a crucial role in promoting muscle health, but our understanding of nuclear proteins orchestrating the molecular response to exercise is limited. Isolation of skeletal muscle nuclei coupled with mass spectrometry enhanced the identification of nuclear proteins. This approach was used to investigate the temporal changes in the muscle nuclear proteome postexercise, including proteins linked to posttranscriptional processing and nuclear transport. Our findings offer new insights into potential mechanisms contributing to exercise-induced adaptations.