PROTEIN PHOSPHATASE-1 IN THE KIDNEY - EVIDENCE FOR A ROLE IN THE REGULATION OF MEDULLARY NA+-K+-ATPASE
PROTEIN PHOSPHATASE-1 IN THE KIDNEY - EVIDENCE FOR A ROLE IN THE REGULATION OF MEDULLARY NA+-K+-ATPASE
复制标题
DOI：
10.1152/ajprenal.1995.269.5.f673
复制
发表时间：
1995-11-01
期刊：
影响因子：
--
通讯作者：
MEISTER, B
中科院分区：
文献类型：
--
作者：
LI, DL;APERIA, A;MEISTER, B
以往的研究表明，肾Na+-K+-ATP酶的激素调节的钠泵的活性调节磷酸化-去磷酸化反应。本文报道蛋白磷酸酶（PP）-1和PP-2A抑制剂冈田酸（OA）和花萼素A（CL-A）对大鼠Henle袢粗升支（TAL）细胞Na ~+-K ~+-ATP酶活性的抑制作用，并呈剂量依赖性。CL-A的效力是OA的10倍。根据CL-A和OA对PP-1和PP-2A的抑制常数，可以得出结论，小管效应主要是由于PP-1的抑制。用寡核苷酸探针进行的原位杂交研究显示，在外髓的外条中有非常强的PP-1 α和PP-1 γ（1）mRNA标记，在外髓的内条中有强标记，在内髓中有弱标记。外皮层的标记非常弱。PP-1 β mRNA在外髓的内条中的标记非常强，而外条的标记较弱，内髓的标记较弱。PP-1 α、PP-1 β和PP-1 γ（1）mRNA也在输尿管移行上皮中被证实。通过免疫印迹法测量的PP-1 α和PP-1 γ同种型的丰度在来自外髓质的组织中非常高，其也具有高丰度的内源性多巴胺调节的PP-1抑制剂DARPP-32。OA和D-1激动剂非诺多泮对Na+-K+-ATP酶活性无协同抑制作用，但对Na +-K+-ATP酶活性有相加抑制作用，提示抑制PP-1是多巴胺抑制延髓TAL Na+-K+-ATP酶活性的机制之一。结果支持DARPP-32/PP-1系统在Henle袢TAL Na+-K+-ATP酶的调节中起重要作用的观点。
Previous studies of hormonal regulation of renal Na+-K+-ATPase have indicated that the activity of the sodium pump is regulated by phosphorylation-dephosphorylation reactions. Here we report that okadaic acid (OA) and calyculin A (CL-A), inhibitors of protein phosphatase (PP)-1 and PP-2A, inhibited Na+-K+-ATPase activity in cells from the rat thick ascending limb (TAL) of loop of Henle in a dose-dependent manner. CL-A was 10-fold more potent than OA. On the basis of the inhibitory constant values of CL-A and OA for PP-1 and PP-2A, it is concluded that the tubular effect is mainly due to inhibition of PP-1. In situ hybridization studies with oligonucleotide probes revealed very strong PP-1 alpha and PP-1 gamma(1) mRNA labeling in the outer stripe of the outer medulla, strong labeling in the inner stripe of the outer medulla, and weak labeling in the inner medulla. Very weak labeling was demonstrated in the outer cortex. PP-1 beta mRNA labeling was very strong in the inner stripe of the outer medulla, whereas the outer stripe had weaker labeling, and the inner medulla had weak labeling. PP-1 alpha, PP-1 beta, and PP-1 gamma(1) mRNA were also demonstrated in the transitional epithelium of the ureter. The abundance of the PP-1 alpha and PP-1 gamma isoforms as measured by immunoblotting was very high in tissue from the outer medulla, which also has a high abundance of the endogenous dopamine-regulated PP-1 inhibitor, DARPP-32. OA and fenoldopam (D-1 agonist) had no synergistic but an additive inhibitory effect on Na+-K+-ATPase activity, suggesting that inhibition of PP-1 is one of the mechanisms of dopamine inhibition of Na+-K+-ATPase activity in the medullary TAL. The results support the concept that the DARPP-32/PP-1 system plays an important role in the regulation of Na+-K+-ATPase in the TAL of the loop of Henle.