Collazo R, Fan L, Hu M C, Zhao H, Wiederkehr M R, Moe O W
Medical Service, Department of Veterans Affairs Medical Center and Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75235, USA.
J Biol Chem. 2000 Oct 13;275(41):31601-8. doi: 10.1074/jbc.M000600200.
Parathyroid hormone (PTH) is a potent inhibitor of mammalian renal proximal tubule Na(+) transport via its action on the apical membrane Na(+)/H(+) exchanger NHE3. In the opossum kidney cell line, inhibition of NHE3 activity was detected from 5 to 45 min after PTH addition. Increase in NHE3 phosphorylation on multiple serines was evident after 5 min of PTH, but decrease in surface NHE3 antigen was not detectable until after 30 min of PTH. The decrease in surface NHE3 antigen was due to increased NHE3 endocytosis. When endocytic trafficking was arrested with a dominant negative dynamin mutant (K44A), the early inhibition (5 min) of NHE3 activity by PTH was not affected, whereas the late inhibition (30 min) and decreased surface NHE3 antigen induced by PTH were abrogated. We conclude that PTH acutely inhibits NHE3 activity in a biphasic fashion by NHE3 phosphorylation followed by dynamin-dependent endocytosis.
甲状旁腺激素（PTH）通过作用于顶端膜钠/氢交换体NHE3，对哺乳动物肾近端小管钠转运具有强大的抑制作用。在负鼠肾细胞系中，添加PTH后5至45分钟可检测到NHE3活性受到抑制。PTH作用5分钟后，多个丝氨酸位点的NHE3磷酸化明显增加，但直到PTH作用30分钟后，表面NHE3抗原才出现减少。表面NHE3抗原的减少是由于NHE3内吞作用增强所致。当用显性负性发动蛋白突变体（K44A）阻止内吞运输时，PTH对NHE3活性的早期抑制（5分钟）不受影响，而PTH诱导的晚期抑制（30分钟）和表面NHE3抗原减少则被消除。我们得出结论，PTH通过NHE3磷酸化随后依赖发动蛋白的内吞作用，以双相方式急性抑制NHE3活性。
