Richards Jeff G, Semple Jeffrey W, Bystriansky Jason S, Schulte Patricia M
Department of Zoology, The University of British Columbia, Vancouver, British Columbia, Canada, V6T 1Z4.
J Exp Biol. 2003 Dec;206(Pt 24):4475-86. doi: 10.1242/jeb.00701.
We identified five Na+/K+-ATPase alpha-isoforms in rainbow trout and characterized their expression pattern in gills following seawater transfer. Three of these isoforms were closely related to other vertebrate alpha1 isoforms (designated alpha1a, alpha1b and alpha1c), one isoform was closely related to alpha2 isoforms (designated alpha2) and the fifth was closely related to alpha3 isoforms (designated alpha3). Na+/K+-ATPase alpha1c- and alpha3-isoforms were present in all tissues examined, while all others had tissue specific distributions. Four Na+/K+-ATPase alpha-isoforms were expressed in trout gills (alpha1a, alpha1b, alpha1c and alpha3). Na+/K+-ATPase alpha1c- and alpha3-isoforms were expressed at low levels in freshwater trout gills and their expression pattern did not change following transfer to 40% or 80% seawater. Na+/K+-ATPase alpha1a and alpha1b were differentially expressed following seawater transfer. Transfer from freshwater to 40% and 80% seawater decreased gill Na+/K+-ATPase alpha1a mRNA, while transfer from freshwater to 80% seawater caused a transient increase in Na+/K+-ATPase alpha1b mRNA. These changes in isoform distribution were accompanied by an increase in gill Na+/K+-ATPase enzyme activity by 10 days after transfer to 80% seawater, though no significant change occurred following transfer to 40% seawater. Isoform switching in trout gills following salinity transfer suggests that the Na+/K+-ATPase alpha1a- and alpha1b-isoforms play different roles in freshwater and seawater acclimation, and that assays of Na+/K+-ATPase enzyme activity may not provide a complete picture of the role of this protein in seawater transfer.
我们在虹鳟鱼中鉴定出了五种钠钾ATP酶α亚基异构体，并对其在转入海水后鳃中的表达模式进行了表征。其中三种异构体与其他脊椎动物的α1亚基异构体密切相关（分别命名为α1a、α1b和α1c），一种异构体与α2亚基异构体密切相关（命名为α2），第五种与α3亚基异构体密切相关（命名为α3）。钠钾ATP酶α1c亚基异构体和α3亚基异构体存在于所有检测的组织中，而其他所有异构体都有组织特异性分布。四种钠钾ATP酶α亚基异构体在鳟鱼鳃中表达（α1a、α1b、α1c和α3）。钠钾ATP酶α1c亚基异构体和α3亚基异构体在淡水鳟鱼鳃中的表达水平较低，转入40%或80%海水后其表达模式没有变化。转入海水后，钠钾ATP酶α1a和α1b亚基异构体的表达存在差异。从淡水转入40%和80%海水会使鳃中钠钾ATP酶α1a mRNA水平降低，而从淡水转入80%海水会使钠钾ATP酶α1b mRNA水平短暂升高。异构体分布的这些变化伴随着转入80%海水10天后鳃中钠钾ATP酶活性增加，不过转入40%海水后没有显著变化。盐度转移后鳟鱼鳃中的异构体转换表明，钠钾ATP酶α1a亚基异构体和α1b亚基异构体在淡水和海水适应过程中发挥不同作用，并且钠钾ATP酶活性测定可能无法全面反映该蛋白在海水转移中的作用。
