Abstract: Objective To study the protein degradation mechanism of the small nucleolar ribonucleoprotein RRP9. Methods Tissue expression profiling was used to analyze the species-specific and tissue-specific expression of RRP9 in normal tissues of mice and humans, and the differential expression of RRP9 in normal colorectal tissues and colorectal cancer tissues. Cycloheximide (CHX), a protein synthesis inhibitor, was used to detect the half-life of RRP9 in colorectal cancer cells. After inhibiting the autophagy-lysosome pathway, the expression of RRP9 was detected to understand the effect of autophagy-lysosomal pathway on RRP9. Finally, immunofluorescence and co-immunoprecipitation were used to detect the interaction between LC3b and RRP9. Results RRP9 is a long-lived protein. Inhibition of autophagy-lysosomal pathway increased the level of RRP9. There was an interaction between RRP9 protein and LC3b in colorectal cancer cells. Conclusion The autophagy-lysosomal pathway regulates the degradation of RRP9 protein.

Key words: colorectal cancer, RRP9, autophagy-lysosomal pathway