Role of Selenoprotein P in Male Fertility

说明(申请人提供)：硒是维持男性生育能力所必需的膳食微量营养素。硒通过硒蛋白发挥其生理活性，这些硒蛋白在其一级结构中含有化学计量数量的硒，如硒半胱氨酸。缺硒动物的附睾精子表现出活力丧失和各种缺陷，包括线粒体鞘的异常和鞭毛纤维的紊乱；我们的研究表明，这些缺陷依次出现在精子发生和睾丸成熟后，突显了硒在睾丸和附睾中的作用。在膳食缺硒期间，睾丸和精子中的硒浓度高于其他组织，并且睾丸的硒含量维持的时间比其他器官长。因此，睾丸有一种机制，与之有效地竞争动物体内的硒，以支持精子的发育。硒蛋白P(Se-P)是一种胞外硒蛋白，占血浆中硒的大部分。我们已经培育出了Se-P缺失的小鼠，纯合的雄性小鼠是不育的。Se-P基因缺失小鼠的睾丸硒水平极低，补硒不能提高睾丸硒水平。Se-P缺陷型动物的精子细胞和附睾精子存在缺硒的结构缺陷。我们的中心假设是，Se-P向睾丸和附睾的特定细胞类型提供硒，以支持正常精子发育所需的硒蛋白合成。这项研究的具体目的是： 目的1：通过确定Se-P在睾丸和附睾中的定位，阐明Se-P在精子发生和睾丸后精子发育中的潜在作用。 目的2：确定Se-P是否为生精小管和附睾管提供硒以用于其他硒蛋白的生物合成。 目的3：鉴定和定位睾丸和附睾中的Se-P结合蛋白。 目的4：探讨Se-P基因缺失小鼠精子缺陷的分子基础。

DESCRIPTION (provided by applicant): Selenium is an essential dietary micronutrient required to maintain male fertility. Selenium exerts its physiological activity through selenoproteins that contain stochiometric amounts of selenium, as selenocysteine, in their primary structure. Epididymal spermatozoa of selenium deficient animals exhibit a loss of motility and display various defects including abnormalities of the mitochondrial sheath and disorganization of the flagellar fibers; our studies demonstrate the defects appear sequentially during spermiogenesis and post-testicular maturation underscoring roles for selenium in both the testis and epididymis. Selenium concentrations of the testis and spermatozoa are higher than other tissues, and the testis maintains its selenium content longer than other organs during dietary selenium deficiency. Thus the testis has a mechanism with which it competes effectively for selenium within the animal to support sperm development. Selenoprotein P (Se-P) is an extracellular selenoprotein that accounts for most of the selenium in plasma. We have produced Se-P null mice and the homozygous males are infertile. Testis selenium levels of Se-P null mice are extremely low and not elevated by selenium supplementation. Spermatids and epididymal spermatozoa of Se-P null animals exhibit structural defects of selenium deficiency. Our central hypothesis is that Se-P provides selenium to specific cell types of the testis and epididymis to support selenoprotein synthesis required for normal sperm development. The specific aims of this study are: Aim 1: To elucidate the potential roles of Se-P in spermiogenesis and post-testicular sperm development by defining its localization in the testis and epididymis. Aim 2: To determine if Se-P provides selenium to the seminiferous and epididymal tubules for biosynthesis of other selenoproteins. Aim 3: To identify and localize Se-P-binding proteins in the testis and epididymis. Aim 4: To determine the molecular basis for sperm defects in Se-P null mice.