Immunological characterization of two types of ionocytes in the inner ear epithelium of Pacific Chub Mackerel (Scomber japonicus)
Immunological characterization of two types of ionocytes in the inner ear epithelium of Pacific Chub Mackerel (Scomber japonicus)
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DOI：
10.1007/s00360-020-01276-3
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发表时间：
2020-05-28
影响因子：
2
通讯作者：
Tresguerres, Martin
中科院分区：
文献类型：
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作者：
Kwan, Garfield T.;Smith, Taylor R.;Tresguerres, Martin
内耳对于维持平衡和在环境中听到捕食者和猎物是必不可少的。每个内耳包含三个CaCO3耳石多晶体，它们在周围上皮分泌的富含K+的碱性内淋巴中钙化。然而，人们对潜在的细胞机制知之甚少，特别是在海鱼中。在这里，我们研究了几种离子转运蛋白在太平洋鳗(Scomber Japan Onicus)球囊上皮内的存在和细胞定位。Western blotting检测到Na+/K+-ATPase(NKA)、碳酸酐酶(CA)、Na+-K+-2Cl(-)-共转运体(NKCC)、液泡型H+-ATPase(VHA)、质膜Ca~(2+)-ATPase(PMCA)和可溶性腺苷环化酶(SAC)的存在。免疫组织化学分析发现球囊上皮有两种不同的离子细胞类型：I型离子细胞富含线粒体，在基底膜上大量表达NKA和NKCC，提示其在内淋巴分泌K+的过程中起作用。另一方面，II型离子细胞富含胞浆中的CA和VHA，表明它们有助于将HCO3-转运到内淋巴并清除H+。此外，这两种类型的离子细胞都表达细胞质PMCA和SAC，PMCA可能参与钙离子的运输和动态平衡，SAC是一种进化保守的酸碱敏感酶，调节上皮离子的运输。此外，CA、VHA和SAC也在向网状区供血的毛细血管中表达，这表明有助于耳石钙化的其他机制。这些信息提高了我们对内淋巴离子调节和耳石形成的细胞机制的了解，并有助于理解对海洋酸化等环境应激源的反应。
The inner ear is essential for maintaining balance and hearing predator and prey in the environment. Each inner ear contains three CaCO3 otolith polycrystals, which are calcified within an alkaline, K+-rich endolymph secreted by the surrounding epithelium. However, the underlying cellular mechanisms are poorly understood, especially in marine fish. Here, we investigated the presence and cellular localization of several ion-transporting proteins within the saccular epithelium of the Pacific Chub Mackerel (Scomber japonicus). Western blotting revealed the presence of Na+/K+-ATPase (NKA), carbonic anhydrase (CA), Na+-K+-2Cl(-)-co-transporter (NKCC), vacuolar-type H+-ATPase (VHA), plasma membrane Ca2+ ATPase (PMCA), and soluble adenylyl cyclase (sAC). Immunohistochemistry analysis identified two distinct ionocytes types in the saccular epithelium: Type-I ionocytes were mitochondrion-rich and abundantly expressed NKA and NKCC in their basolateral membrane, indicating a role in secreting K+ into the endolymph. On the other hand, Type-II ionocytes were enriched in cytoplasmic CA and VHA, suggesting they help transport HCO3- into the endolymph and remove H+. In addition, both types of ionocytes expressed cytoplasmic PMCA, which is likely involved in Ca2+ transport and homeostasis, as well as sAC, an evolutionary conserved acid-base sensing enzyme that regulates epithelial ion transport. Furthermore, CA, VHA, and sAC were also expressed within the capillaries that supply blood to the meshwork area, suggesting additional mechanisms that contribute to otolith calcification. This information improves our knowledge about the cellular mechanisms responsible for endolymph ion regulation and otolith formation, and can help understand responses to environmental stressors such as ocean acidification.