Biochemical changes in the transition from vitellogenesis to follicular atresia in the hematophagous Dipetalogaster maxima (Hemiptera: Reduviidae)
Biochemical changes in the transition from vitellogenesis to follicular atresia in the hematophagous Dipetalogaster maxima (Hemiptera: Reduviidae)
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DOI：
10.1016/j.ibmb.2011.06.005
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发表时间：
2011-10-01
影响因子：
3.8
通讯作者：
Canavoso, Lilian E.
中科院分区：
文献类型：
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作者：
Aguirre, Silvina A.;Fruttero, Leonardo L.;Canavoso, Lilian E.
在这项工作中，我们探索了从卵黄发生到卵泡闭锁转变的生化变化，以食血昆虫载体Dipetalogaster Maxima为模型。建立了标准化的昆虫饲养条件，通过在卵黄发生后剥夺雌性昆虫的血食来诱导逐渐的卵泡退化阶段。在这项研究中，血淋巴和卵巢在卵黄形成前、卵黄形成和卵泡闭锁早期和晚期的代表性天数进行了采样。扫描电子显微镜检查，闭锁初期的卵巢小，但仍表现出一定程度的不同步，这一特征在晚期变性状态下消失。在卵泡闭锁晚期，体内摄取荧光标记的卵黄蛋白原(VG-FITC)的检测显示卵母细胞对摄取卵黄蛋白的竞争性丧失。闭锁患者循环中的卵黄蛋白原水平显著高于卵黄发生前的水平，如果有第二餐供血，很有可能维持另一个促性腺周期的合适条件。卵泡闭锁的特征还表现为卵黄蛋白的部分降解，Western印迹显示卵泡闭锁的卵巢匀浆中有卵黄蛋白的部分降解。当检测卵巢肽酶对血红蛋白(一种非特异性底物)的活性时，在闭锁早期和晚期活性较高，而在卵黄形成时活性最低。天冬氨酸氨基转移酶抑制剂胃抑素A对Hb的活性有显著抑制作用，而半胱氨酸肽酶抑制剂E64在任何实验条件下均不影响其活性。特殊荧光底物的使用表明，早期卵泡闭锁的卵巢匀浆显示出较高的组织蛋白酶D样活性，而组织蛋白酶B和L均未检测到活性。对底物Abz-AIAFSRQ-EDDnp的消化产物的质谱分析进一步证实了卵巢组织中存在组织蛋白酶D样肽酶。根据我们的发现，组织蛋白酶D样肽酶的早期激活可能与促进卵黄蛋白循环和/或促进毛囊去除有关。(C)2011爱思唯尔有限公司。保留所有权利。
In this work, we have explored the biochemical changes characterizing the transition from vitellogenesis to follicular atresia, employing the hematophagous insect vector Dipetalogaster maxima as a model. Standardized insect rearing conditions were established to induce a gradual follicular degeneration stage by depriving females of blood meal during post-vitellogenesis. For the studies, hemolymph and ovaries were sampled at representative days of pre-vitellogenesis, vitellogenesis and early and late follicular atresia. When examined by scanning electron microscopy, ovarioles at the initial stage of atresia were small but still showed some degree of asynchronism, a feature that was lost in an advanced degeneration state. At late follicular atresia, in vivo uptake assays of fluorescently labeled vitellogenin (Vg-FITC) showed loss of competitiveness of oocytes to uptake vitellogenin. Circulating vitellogenin levels in atresia were significantly higher than those registered at pre-vitellogenesis, most likely to maintain appropriate conditions for another gonotrophic cycle if a second blood meal is available. Follicular atresia was also characterized by partial proteolysis of vitellin, which was evidenced in ovarian homogenates by western blot. When the activity of ovarian peptidases upon hemoglobin (a non-specific substrate) was tested, higher activities were detected at early and late atresia whereas the lowest activity was found at vitellogenesis. The activity upon hemoglobin was significantly inhibited by pepstatin A (an aspartic peptidase inhibitor), and was not affected by E64 (a cysteine peptidase inhibitor) at any tested conditions. The use of specific fluorogenic substrates demonstrated that ovarian homogenates at early follicular atresia displayed high cathepsin D-like activity, whereas no activity of either, cathepsin B or L was detected. Mass spectrometry analysis of the digestion products of the substrate Abz-AIAFFSRQ-EDDnp further confirmed the presence of a cathepsin D-like peptidase in ovarian tissue. In the context of our findings, the early activation of cathepsin D-like peptidase could be relevant in promoting yolk protein recycling and/or enhancing follicle removal. (C) 2011 Elsevier Ltd. All rights reserved.