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首页> 外文期刊>American Journal of Physiology >Cathepsin B-mediated yolk protein degradation during killifish oocyte maturation is blocked by an H+-ATPase inhibitor: effects on the hydration mechanism.
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Cathepsin B-mediated yolk protein degradation during killifish oocyte maturation is blocked by an H+-ATPase inhibitor: effects on the hydration mechanism.

机译：H + -ATPase抑制剂阻止了在比目鱼卵母细胞成熟过程中组织蛋白酶B介导的蛋黄蛋白降解：对水合机制的影响。

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In teleost oocytes, yolk proteins (YPs) derived from the yolk precursors vitellogenins are partially cleaved into free amino acids and small peptides during meiotic maturation before ovulation. This process increases the osmotic pressure of the oocyte that drives its hydration, which is essential for the production of buoyant eggs by marine teleosts (pelagophil species). However, this mechanism also occurs in marine species that produce benthic eggs (benthophil), such as the killifish (Fundulus heteroclitus), in which oocyte hydration is driven by K+. Both in pelagophil and benthophil teleosts, the enzymatic machinery underlying the maturation-associated proteolysis of YPs is poorly understood. In this study, lysosomal cysteine proteinases potentially involved in YP processing, cathepsins L, B, and F (CatL, CatB, and CatF, respectively), were immunolocalized in acidic yolk globules of vitellogenic oocytes from the killifish. During oocyte maturation in vitro induced with the maturation-inducing steroid(MIS), CatF disappeared from yolk organelles and CatL became inactivated, whereas CatB proenzyme was processed into active enzyme. Consequently, CatB enzyme activity and hydrolysis of major YPs were enhanced. Follicle-enclosed oocytes incubated with the MIS in the presence of bafilomycin A1, a specific inhibitor of vacuolar-type H+-ATPase, underwent maturation in vitro, but acidification of yolk globules, activation of CatB, and proteolysis of YPs were prevented. In addition, MIS plus bafilomycin A1-treated oocytes accumulated less K+ than those stimulated with MIS alone; hence, oocyte hydration was reduced. These results suggest that CatB is the major protease involved in yolk processing during the maturation of killifish oocytes, whose activation requires acidic conditions maintained by a vacuolar-type H+-ATPase. Also, the data indicate a link between ion translocation and YP proteolysis, suggesting that both events may be equally important physiological mechanisms for oocyte hydration in benthophil teleosts.
机译：在硬骨卵母细胞中，卵黄蛋白前体卵黄蛋白原的卵黄蛋白（YPs）在减数分裂成熟之前，在排卵前被部分切割成游离氨基酸和小肽。此过程会增加卵母细胞的渗透压，从而推动卵母细胞的水合作用，这对于通过海洋硬骨鱼（嗜卵菌）产生浮力卵至关重要。但是，这种机制也发生在生产底栖卵（嗜生性）的海洋物种中，例如，其中的卵母细胞水合作用由K +驱动的幼鱼（Fundulus heteroclitus）。在亲上腹足动物和底生硬骨鱼中，对YPs的成熟相关蛋白水解作用的酶学机制知之甚少。在这项研究中，潜在参与YP加工的溶酶体半胱氨酸蛋白酶，组织蛋白酶L，B和F（分别为CatL，CatB和CatF）被免疫定位在来自比目鱼的卵黄形成卵母细胞的酸性蛋黄小球中。在诱导成熟的类固醇（MIS）诱导的卵母细胞成熟过程中，CatF从卵黄细胞器中消失，CatL失活，而CatB酶被加工成活性酶。因此，增强了CatB酶的活性和主要YP的水解。在巴菲霉素A1（液泡型H + -ATPase的特异性抑制剂）存在下，与MIS一起孵育的卵泡封闭卵母细胞在体外成熟，但可防止卵黄小球酸化，CatB活化和YP的蛋白水解。另外，MIS加经博氟霉素A1处理的卵母细胞比单独用MIS刺激的卵母细胞累积的K +少。因此，卵母细胞的水合作用减少。这些结果表明，CatB是双歧杆菌卵母细胞成熟过程中参与卵黄加工的主要蛋白酶，其活化需要液泡型H + -ATPase维持的酸性条件。此外，数据表明离子易位与YP蛋白水解之间存在联系，这表明这两种事件可能是对底栖硬骨鱼卵母细胞水化的同等重要的生理机制。

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