Differential Activity and Expression of Proteasome in Seminiferous Epithelium During Mouse Spermatogenesis
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2025
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Proteasome-mediated protein degradation is essential for maintaining cellular
homeostasis, particularly during spermatogenesis, where extensive cellular transformations,
such as spermatid differentiation, require precise protein turnover. A key player in
this process is the ubiquitin–proteasome system (UPS). This study aimed to investigate
proteasome enzymatic activity at different stages of the spermatogenic cycle within the
seminiferous tubules of mice and explore the regulatory mechanisms that influence its
proteolytic function. Specifically, we assessed the trypsin-like, chymotrypsin-like, and
peptidyl-glutamyl-peptide-hydrolyzing (PGPH) activities of the proteasome. Additionally,
we examined the expression of catalytic and structural subunits of the 20S core, the
assembly of the 20S core with regulatory complexes, and the phosphorylation status of
proteasome subunits in various segments of the seminiferous tubules. Our findings demonstrated
distinct patterns of proteasomal enzymatic activity in the analyzed segments. While
the expression levels of structural and catalytic subunits of the 20S core remained consistent,
significant differences were detected in the assembly of the 20S core, the expression
of regulatory complexes, and the phosphorylation of proteasome subunits mediated by
protein kinase A. These results indicate that proteasomal activity is finely regulated through
multiple mechanisms depending on the specific stage of the seminiferous epithelial cycle,
highlighting the complexity of proteostasis during spermatogenesis.