Targeting of a germ cell-specific type 1 hexokinase lacking a porin-binding domain to the mitochondria as well as to the head and fibrous sheath of murine spermatozoa
Targeting of a germ cell-specific type 1 hexokinase lacking a porin-binding domain to the mitochondria as well as to the head and fibrous sheath of murine spermatozoa
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DOI：
10.1091/mbc.9.2.263
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发表时间：
1998-02-01
影响因子：
3.3
通讯作者：
Moss, SB
中科院分区：
文献类型：
--
作者：
Travis, AJ;Foster, JA;Moss, SB
在小鼠的精子发生过程中转录了多种类型的1型己糖激酶(HK1)，其中至少有三种可能是生殖细胞特有的：HK1-Sa、HK1-Sb和HK1-Sc。这些预测的蛋白质中的每一个都包含一个共同的生殖细胞特有的序列，该序列取代了在体细胞HK1中发现的孔蛋白结合域。虽然HK1蛋白存在于成熟精子中，并被酪氨酸磷酸化，但目前尚不清楚各种潜在的亚型是否在发育中的生殖细胞和成熟精子中差异翻译和定位。用针对HK1-Sa和HK1-Sb特异区域的抗肽抗血清证明，在粗线期精母细胞、圆形精子细胞、凝集性精子细胞或精子中没有发现这些异构体，这表明HK1-Sa和HK1-Sb在精子发生过程中不被翻译。在圆形精子细胞、浓缩精子细胞和成熟精子的蛋白质中，用抗生精细胞特异区的抗肽抗血清检测到免疫反应，这表明HK1-sc是这些细胞中唯一存在的生殖细胞特异性亚型。双向SDS-PAGE分析表明，所有的精子HK1-sc都是酪氨酸磷酸化的，体细胞HK1亚型不存在。免疫电子显微镜显示，HK1-sc与线粒体和鞭毛纤维鞘联系在一起，在精子头部的膜区呈离散的簇状分布。HK1-sc在精子中的异常分布提示了新的功能，如线粒体外能量产生，也表明没有经典孔蛋白结合区的己糖激酶可以定位在线粒体上。
Multiple isoforms of type 1 hexokinase (HK1) are transcribed during spermatogenesis in the mouse, including at least three that are presumably germ cell specific: HK1-sa, HK1-sb, and HK1-sc. Each of these predicted proteins contains a common, germ cell-specific sequence that replaces the porin-binding domain found in somatic HK1. Although HK1 protein is present in mature sperm and is tyrosine phosphorylated, it is not known whether the various potential isoforms are differentially translated and localized within the developing germ cells and mature sperm. Using antipeptide antisera against unique regions of HK1-sa and HK1-sb, it was demonstrated that these isoforms were not found in pachytene spermatocytes, round spermatids, condensing spermatids, or sperm, suggesting that HK1-sa and HK1-sb are not translated during spermatogenesis. Immunoreactivity was detected in protein from round spermatids, condensing spermatids, and mature sperm using an antipeptide antiserum against the common, germ cell-specific region, suggesting that HK1-sc was the only germ cell-specific isoform present in these cells. Two-dimensional SDS-PAGE suggested that all of the sperm HK1-sc was tyrosine phosphorylated, and that the somatic HK1 isoform was not present. Immunoelectron microscopy revealed that HK1-sc was associated with the mitochondria and with the fibrous sheath of the flagellum and was found in discrete clusters in the region of the membranes of the sperm head. The unusual distribution of HK1-sc in sperm suggests novel functions, such as extramitochondrial energy production, and also demonstrates that a hexokinase without a classical porin-binding domain can localize to mitochondria.