Studies on the extracellular transporting mechanisms of sperm proteasomes and the functions of PA200

2019 Fiscal Year Final Research Report

• Project/Area Number: 17K19520
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Research Field: Biomedical structure and function and related fields
• Research Institution: Nagoya University
• Principal Investigator: Sawada Hitoshi 名古屋大学, 理学研究科, 教授 (60158946)
• Project Period (FY): 2017-06-30 – 2020-03-31
• Keywords: プロテアソーム / 精子 / 受精 / PA200

Outline of Final Research Achievements

We previously reported that sperm proteasomes are involved in sperm penetration of the vitelline coat, probably as a lysin. Here, the localization of sperm proteasome in sperm membrane fraction was re-examined. Furthermore, roles in fertilization of proteasome activator PA200, which appears to be involved in sexual reproduction, was examined. The results showed that sperm proteasome subunits were detected by LC/MS in the immunoprecipitated sperm membrane fraction using anti-proteasome antibody. However, it was not successful to identify the proteasome-associating proteins. Then, targeting of ascidian PA200 genes was carried out by genome editing. However, this was not successful due to the induction of abnormal embryonic development. On the other hand, we noticed that sperm metalloproteases may be involved in ascidian fertilization based on the inhibitory effects on fertilization. This enzyme may also play a key role in fertilization together with the proteasome.

Free Research Field

生化学

Academic Significance and Societal Importance of the Research Achievements

申請者は、受精実験が容易な脊索動物マボヤを用いて、その受精に精子ユビキチン-プロテアソーム系が関与すること、特に細胞外で卵膜ライシンとして機能することを初めて明らかにした。その後、哺乳類や鳥類や棘皮動物でも同様の現象が確認され、新口動物に共通するシステムであると考えられる。一般に、プロテアソームは細胞内のタンパク質分解で重要な役割を果たすが、細胞外での機能は不明な点が多い。しかし、近年、神経疾患等で細胞外プロテアソームが注目されつつある。本研究は、受精に関わる精子プロテアソームの細胞外での機能と輸送機構に焦点を当てた研究であり、不妊症診断治療薬の開発に繋がりうる基礎研究といえる。