Wetzel R K, Sweadner K J
Laboratory of Membrane Biology, Neuroscience Center, Massachusetts General Hospital, 149 13th St., Charlestown, MA 02129, USA.
Am J Physiol Renal Physiol. 2001 Sep;281(3):F531-45. doi: 10.1152/ajprenal.2001.281.3.F531.
The gamma-subunit of the Na-K-ATPase is a single-span membrane protein that alters the kinetic properties of the enzyme. It is expressed in the kidney, but our initial observations indicated that it is not present in all nephron segments (Arystarkhova E, Wetzel RK, Asinovski NK, and Sweadner KJ. J Biol Chem 274: 33183-33185, 1999). Here we used triple-label confocal immunofluorescence microscopy in rat kidney with antibodies to Na-K-ATPase alpha1- and gamma-subunits and nephron segment-specific markers. Na-K-ATPase alpha1-subunit stain was low but unambiguous in proximal segments, moderate in macula densa, connecting tubules, and cortical collecting ducts, high in thick ascending limb and distal convoluted tubules, and nearly undetectable in glomeruli, descending and ascending thin limb, and medullary collecting ducts. The gamma-subunit colocalized at staining levels similar to alpha1-subunit in basolateral membranes in all segments except cortical thick ascending limb and cortical collecting ducts, which had alpha1-subunit but no detectable gamma-subunit stain. Selective gamma-subunit expression may contribute to the variations in Na-K-ATPase properties in different renal segments.
钠钾ATP酶的γ亚基是一种单跨膜蛋白，可改变该酶的动力学特性。它在肾脏中表达，但我们最初的观察表明它并非存在于所有肾单位节段中（Arystarkhova E、Wetzel RK、Asinovski NK和Sweadner KJ。《生物化学杂志》274: 33183 - 33185，1999年）。在此，我们使用三重标记共聚焦免疫荧光显微镜技术，对大鼠肾脏中钠钾ATP酶α1亚基和γ亚基以及肾单位节段特异性标志物进行抗体检测。钠钾ATP酶α1亚基染色在近端节段较低但清晰可辨，在致密斑、连接小管和皮质集合管中中等，在髓袢升支粗段和远曲小管中较高，而在肾小球、髓袢降支细段和升支细段以及髓质集合管中几乎检测不到。除皮质髓袢升支粗段和皮质集合管外，γ亚基在所有节段的基底外侧膜中的染色水平与α1亚基相似，皮质髓袢升支粗段和皮质集合管有α1亚基染色但未检测到γ亚基染色。γ亚基的选择性表达可能导致不同肾节段中钠钾ATP酶特性的差异。
