The Function And Mechanism Of Testis-specific Serine Protease PRSS55 On Male Reproduction

Members of the Prss?protease/serine?gene family encode putative serine protease.Most of the testicular-specific expression members are located in the male germ cell plasma membrane and play an important role in male reproduction.According to the republic reports in the literature,PRSS41,PRSS42 and PRSS43 are directly involved in mouse testicular development and spermatogenesis by regulating meiosis of spermatocytes.The targeted disruption of PRSS21 leads to the inability of sperm to pass through the zona pellucid in vitro fertilization experiment.PRSS37 is required for male fertility in mice by affecting sperm migration from uterus into oviduct and sperm-egg recognition/binding in vitro.The low expression of PRSS37 in human sperm is directly related to unexplained male infertility.The use of gene targeting mouse models is an important and effective mean to study the biological functions of unknown genes.In this paper,we used gene knockout mice to study the role of Prss55 gene in male fertility.PRSS55,also known as testis serine protease?T-SP1?,is a trypsin-like serine protease which specifically expressed in the testis.Prss55 is a testis-specific gene which function is largely unknown in mice.The expression of Prss55 mRNA and protein in the testis can be detected around 4 weeks old or later which along with the sperm maturation.PRSS55 is a GPI-anchored membrane protein in testicular cells and sperm which shows serine protease activity.Prss55 knockout mice were sterile while testis development,spermatogenesis,sperm count,sperm motility,acrosome reaction,acrosome enzyme activity,and mating ability were not affected.In vivo fertilization experiments showed that the fertilization rate of Prss55^-/-sperm decreased significantly compared with wild mice?4.1%vs 82.9%?which accompanied with the defect in sperm migration of the UTJ knots in the female reproductive tract.In vitro fertilization experiments showed that the incapability of sperm in sperm-egg recognition/binding while in vitro fertilization rate was not affected.Further analysis revealed that the ADAM3 mature form completely disappeared in the Prss55^-/-sperm,but its precursor in the testis was not affected and no direct interaction was detected between the PRSS55 and ADAM3 in the testis tissue.The ADAM family encodes germ cell surface proteins involved in the interaction of sperm with extracellular matrix complexes in the female reproductive tract.Up to mow,there are 15 gene knockout mice,including Calr3^-/-,Clgn^-/-,Ace^-/-,Adam6^-/-,Adam3^-/-,Adam2^-/-,Adam1a^-/-,Tpst2^-/-,Pdilt^-/-,Pmis2^-/-,Prss37^-/-,Tex101^-/-,Ly6k^-/-,RNase10^-/-,Pgap1^-/-,showed defect in migration from uterus into oviduct accompaning the disappearance or ectopic of mature ADAM3.So,ADAM3 was thought to be the target molecule that regulates sperm pass through the UTJ junction.As a new regulator of ADAM3,PRSS55 affects male reproduction in mice by participating in the processing maturation of ADAM3.In summary,this study confirmed that the Prss55 gene plays an indispensable role in male reproduction.The clarification of the structure and biological function of PRSS55protein has deepened the functional cognition of GPI-anchored proteins on sperm surface and expanded the range of function of serine protease family members in male reproductive process.The phenotype of Prss55^-/-male is consistent with the pathological features of clinically unexplained infertility?UMI?patients.The sequence of PRSS55protein is highly conserved among different species,and the expression pattern of PRSS55in human is testsi-specific which indicates that PRSS55 may play a similar function in human reproduction.Therefore,the exploration of PRSS55 function and molecular mechanism underlying phenotype will provide potential targets for diagnosis and treatment of clinical UMI patients,and also provide a theoretical basis for the development of new contraceptives.