Division of Animal Sciences, University of Missouri, Columbia, MO, 65211-5300, USA.
Laboratory of Reproductive Biology, Institute of Biotechnology, CAS, v.v.i, 25242, Vestec, Czech Republic.
Cell Tissue Res. 2018 Jun;372(3):591-601. doi: 10.1007/s00441-017-2786-6. Epub 2018 Jan 29.
Protein ubiquitination is a stable, reversible post-translational modification, targeting proteins for degradation/recycling by the 26S proteasome in a well-characterized enzymatic cascade. Studies have revealed the role of UPS in the regulation of fertilization, including sperm-zona pellucida interactions and the early event of sperm capacitation. The present study investigates the changes in proteasome compartmentalization, subunit composition and post-translational modifications during in vitro capacitation of fresh boar spermatozoa. We observed capacitation-dependent shedding of both 20S core and 19S regulatory particles from the acrosome that was associated with decreased plasma membrane integrity, independent of proteasomal inhibition. Subunits PSMA1-7 of the 20S core did not appear to undergo post-translational modifications during capacitation, based on invariant molecular masses before and after capacitation; however, we observed multiple PSMD4 forms of 19S regulatory particles (50, 53, 70, 115-140, 160 and >176 kDa) sequentially released from spermatozoa. PSMD4 subunit was found to be post-translationally modified during the course of capacitation, resulting in changes of apparent molecular mass, some of which were dependent on proteasomal inhibition. These results show that the sperm proteasomes are being modified during sperm capacitation. Additional studies of individual 26S proteasome subunits will be required to elucidate these modifications and to understand how UPS modulates sperm capacitation.
蛋白质泛素化是一种稳定的、可逆转的翻译后修饰，通过特征明确的酶级联反应将蛋白质靶向到 26S 蛋白酶体进行降解/回收。研究揭示了 UPS 在受精调节中的作用，包括精子-透明带相互作用和精子获能的早期事件。本研究探讨了新鲜猪精子体外获能过程中蛋白酶体区室化、亚基组成和翻译后修饰的变化。我们观察到，顶体的 20S 核心和 19S 调节颗粒在获能过程中依赖性脱落，这与质膜完整性的降低有关，与蛋白酶体抑制无关。基于获能前后不变的分子量，我们观察到 20S 核心的 PSMA1-7 亚基在获能过程中没有发生翻译后修饰；然而，我们观察到 19S 调节颗粒（50、53、70、115-140、160 和>176 kDa）的多个 PSMD4 形式从精子中顺序释放。发现 PSMD4 亚基在获能过程中发生了翻译后修饰，导致表观分子量发生变化，其中一些变化依赖于蛋白酶体抑制。这些结果表明，精子蛋白酶体在精子获能过程中发生了修饰。需要进一步研究单个 26S 蛋白酶体亚基，以阐明这些修饰，并了解 UPS 如何调节精子获能。
