Cloning and immunolocalization of a rat pancreatic Na(+) bicarbonate cotransporter.
Cloning and immunolocalization of a rat pancreatic Na(+) bicarbonate cotransporter.
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DOI：
10.1006/bbrc.1999.1484
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发表时间：
1999-10
影响因子：
3.1
通讯作者：
F. Thévenod;E. Roussa;B. Schmitt;Michael F. Romero
中科院分区：
文献类型：
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作者：
F. Thévenod;E. Roussa;B. Schmitt;Michael F. Romero
在大鼠中，胰腺HCO(-)(3)的分泌被认为是由导管细胞介导的，其中顶端的Cl(-)/HCO(-)(3)交换器与cAMP激活的Cl(-)通道平行作用，质子通过底侧的Na(+)/H(+)交换器排出。然而，这可能不是大鼠胰腺分泌HCO(-)(3)的唯一机制。最近，一些生电Na(+)/HCO(-)(3)共转运蛋白(NBC)已被克隆。在此，我们报道了从大鼠胰腺中克隆的NBC(RpNBC)。这种rpNBC与更长、更常见的NBC形式有99%的同源性[pNBC；1079个氨基酸(AA)；在人的心脏、胰腺、前列腺中有122 kDa，在肾脏中有一个小克隆]。较长的NBC亚型在大约980个C-末端氨基酸上与大鼠和人类肾脏特异的亚型(KNBC；1035个氨基酸；116 kDa)相同，在初始N-末端是唯一的(长度不同)。用抗大鼠肾NBC共同N-末端和C-末端的多克隆抗体，免疫印迹大鼠胰腺组织匀浆，标记一条约130 kDa的蛋白条带，并富集于细胞膜部分。免疫荧光和免疫过氧化物酶光镜观察两种抗体的大鼠胰腺组织均可见腺泡细胞的基底侧方标记。在中央腺泡细胞、小叶内外导管和主管细胞中均可见根尖和基底侧膜的标记。融合蛋白用于免疫的抗体预吸收实验证实了抗体标记的特异性。这些数据表明，rpNBC在大鼠胰腺腺泡和导管细胞转运HCO(-)(3)的过程中可能起着比先前认为的更重要的作用。
In the rat, pancreatic HCO(-)(3) secretion is believed to be mediated by duct cells with an apical Cl(-)/HCO(-)(3) exchanger acting in parallel with a cAMP-activated Cl(-) channel and protons being extruded through a basolateral Na(+)/H(+) exchanger. However, this may not be the only mechanism for HCO(-)(3) secretion by the rat pancreas. Recently, several members of electrogenic Na(+)/HCO(-)(3) cotransporters (NBC) have been cloned. Here we report the cloning of a NBC from rat pancreas (rpNBC). This rpNBC is 99% identical to the longer, more common form of NBC [pNBC; 1079 amino acids (aa); 122 kDa in human heart, pancreas, prostate, and a minor clone in kidney]. The longer NBC isoforms are identical to the rat and human kidney-specific forms (kNBC; 1035 aa; 116 kDa) at the approximately 980 C-terminal aa's and are unique (with different lengths) at the initial N-terminus. Using polyclonal antibodies to the common N- and C-termini of rat kidney NBC, a approximately 130-kDa protein band was labeled by immunoblotting of rat pancreas homogenate and was enriched in the plasma membrane fraction. Immunofluorescence and immunoperoxidase light microscopy of rat pancreatic tissue with both antibodies revealed basolateral labeling of acinar cells. Labeling of both apical and basolateral membranes was found in centroacinar cells, intra- and extralobular duct, and main duct cells. The specificity of the antibody labeling was confirmed by antibody preabsorption experiments with the fusion protein used for immunization. The data suggest that rpNBC likely plays a more important role in the transport of HCO(-)(3) by rat pancreatic acinar and duct cells than previously believed.