Zlokovic B V, Mackic J B, Wang L, McComb J G, McDonough A
Department of Neurosurgery, Childrens Hospital Los Angeles, USC School of Medicine 90033.
J Biol Chem. 1993 Apr 15;268(11):8019-25.
The relative levels of expression of Na,K-ATPase alpha and beta subunit isoforms were determined in rat cerebral microvessels, choroid plexus, and capillary-depleted brain homogenates by Western blot analysis. Three alpha (alpha 1, alpha 2, alpha 3) and two beta (beta 1, beta 2) subunits were detected in brain as previously reported. All 3 alpha and 2 beta isoforms were also found in microvessels. The choroid plexus expressed alpha 1, beta 1, and beta 2, while alpha 2 and alpha 3 were not found. Autoradiographic signals were normalized to a constant amount of protein from the 3 tissues to calculate relative levels of expression. Expression of alpha 1, alpha 2, and alpha 3 was higher in microvessels than in the brain, by 1.7-, 1.2-, and 1.2-fold, respectively, but expression of beta 1 and beta 2 was 5.5-fold lower. alpha 1 was 4-fold higher in the choroid plexus than in the brain, while expression of beta 1 and beta 2 was 15- and 5.5-fold lower, respectively. Na,K-ATPase enzymatic activities in microvessels and choroid plexus homogenates were similar and 5-fold lower than in brain homogenate. We conclude that: (a) expression of functionally active Na,K-ATPase isoenzymes in microvessels and choroid plexus is restricted in comparison to the brain possibly due to a limited pool of beta 1 and beta 2 subunits; (b) six structurally distinct Na,K-ATPase isoenzymes may be expressed in cerebral microvessels and two in the choroid plexus.
通过蛋白质免疫印迹分析，测定了大鼠脑微血管、脉络丛和去除毛细血管的脑匀浆中钠钾ATP酶α和β亚基同工型的相对表达水平。如先前报道，在脑中检测到三种α亚基（α1、α2、α3）和两种β亚基（β1、β2）。在微血管中也发现了所有三种α亚基和两种β亚基。脉络丛表达α1、β1和β2，而未发现α2和α3。将放射自显影信号标准化为来自这三种组织的恒定蛋白量，以计算相对表达水平。微血管中α1、α2和α3的表达分别比脑中高1.7倍、1.2倍和1.2倍，但β1和β2的表达低5.5倍。脉络丛中α1的表达比脑中高4倍，而β1和β2的表达分别低15倍和5.5倍。微血管和脉络丛匀浆中的钠钾ATP酶活性相似，比脑匀浆低5倍。我们得出以下结论：（a）与脑相比，微血管和脉络丛中功能活性钠钾ATP酶同工酶的表达可能受到限制，这可能是由于β1和β2亚基的储备有限；（b）六种结构不同的钠钾ATP酶同工酶可能在脑微血管中表达，两种在脉络丛中表达。
