PDF(Pubmed)
Abstract：
Life in fresh water is osmotically and energetically challenging for living organisms, requiring increases in ion uptake from dilute environments. However, mechanisms of ion uptake from freshwater environments are still poorly understood and controversial, especially in arthropods, for which several hypothetical models have been proposed based on incomplete data. One compelling model involves the proton pump V-type H+ ATPase (VHA), which energizes the apical membrane, enabling the uptake of Na+ (and other cations) via an unknown Na+ transporter (referred to as the \"Wieczorek Exchanger\" in insects). What evidence exists for this model of ion uptake and what is this mystery exchanger or channel that cooperates with VHA? We present results from studies that explore this question in crustaceans, insects, and teleost fish. We argue that the Na+/H+ antiporter (NHA) is a likely candidate for the Wieczorek Exchanger in many crustaceans and insects; although, there is no evidence that this is the case for fish. NHA was discovered relatively recently in animals and its functions have not been well characterized. Teleost fish exhibit redundancy of Na+ uptake pathways at the gill level, performed by different ion transporter paralogs in diverse cell types, apparently enabling tolerance of low environmental salinity and various pH levels. We argue that much more research is needed on overall mechanisms of ion uptake from freshwater habitats, especially on NHA and other potential Wieczorek Exchangers. Such insights gained would contribute greatly to our general understanding of ionic regulation in diverse species across habitats.
摘要：
淡水中的生命对生物体在渗透和能量上都具有挑战性，需要增加从稀薄环境中的离子吸收。然而,从淡水环境中吸收离子的机制仍然知之甚少和有争议，尤其是在节肢动物中，为此，已经基于不完整的数据提出了几个假设模型。一个引人注目的模型涉及质子泵V型HATPase（VHA），为根尖膜提供能量，能够通过未知的Na转运蛋白（在昆虫中称为“Wieczorek交换器”）吸收Na（和其他阳离子）。这种离子吸收模型有什么证据，这种与VHA合作的神秘交换体或通道是什么？我们提出了在甲壳类动物中探索这一问题的研究结果，昆虫,和硬骨鱼。我们认为Na/H反转运蛋白（NHA）可能是许多甲壳类动物和昆虫中Wieczorek交换器的候选者；尽管，没有证据表明鱼就是这种情况。NHA是最近在动物中发现的，其功能尚未得到很好的表征。硬骨鱼在g水平上表现出Na吸收途径的冗余，由不同的离子转运蛋白旁系同源物在不同的细胞类型中进行，显然能够耐受低环境盐度和各种pH水平。我们认为，需要对从淡水栖息地吸收离子的总体机制进行更多的研究，尤其是NHA和其他潜在的Wieczorek交易所。获得的这些见解将极大地有助于我们对栖息地不同物种中离子调节的一般理解。
