Ovastacin and analysis of the proteolytic network of egg-sperm interaction in mammals

• Applicant: Dr. Hagen Körschgen
• Subject Area: Reproductive Medicine, Urology ; Biochemistry ; Animal Physiology and Biochemistry
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 463432843

The precise regulation of proteolytic enzymes during egg-sperm interaction is substantial for successful fertilization in mammals. The astacin-like metalloprotease ovastacin is released during the cortical reaction and cleaves the zona pellucida protein 2 within the egg-surrounding matrix. The resulting reorganisation of the egg envelope prevents binding and penetration of further spermatozoa. The activity of ovastacin is strictly controlled by the plasma protein fetuin-B. In absence of this inhibitor the egg envelope becomes impermeable for sperm even prior fertilization. This results in female infertility. Other proteases such as acrosin are also known to be necessary for fertilization. However, the physiological substrates, functions and other components of this proteolytic network are still unknown.One aim of the project is the identification of physiological substrates ex vivo in the secretome of murine germ cells before and after egg-sperm interaction. Therefore neo-N-termini of proteins are determined by mass spectrometry using the method TAILS (Terminal Amine Isotopic Labeling of Substrates). Due to the characteristic and distinct cleavage specificity of ovastacin, we will first perform the analysis for this enzyme and as a next step for the serine protease acrosine. We expect to gain fundamental new insights into the complex proteolytic network that controls fertilization in mammals.We are also looking for answers to the question whether specific, low-molecular inhibitors of ovastacin can be used to regulate the proteolytic network of fertilization. It has already been shown that the supplementation of fetuin-B extends the period for successful fertilization in vitro. This could circumvent the limitations of a proteinogenic inhibitor.

• DFG Programme: Research Grants