Potter L R, Garbers D L
Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee 37232.
J Biol Chem. 1992 Jul 25;267(21):14531-4.
Atrial natriuretic peptide (ANP) binds to the guanylyl cyclase-A (GC-A) receptor found in tissues such as the kidney and adrenal gland, resulting in marked elevations of the intracellular signaling molecule, cGMP. Here, GC-A is shown to exist as a phosphoprotein when expressed in human embryonic 293 cells. The 32P is principally associated with phosphoserine, with only trace amounts of phosphothreonine. The addition of ANP causes a time-dependent dephosphorylation of the receptor, as well as desensitization, which is not due to an ANP-mediated decrease in the amount of receptor protein. The mobility of GC-A on sodium dodecyl sulfate-polyacrylamide gel electrophoresis increases after treatment of cells with ANP, and protein phosphatase 2A induces the same mobility shift. The protein phosphatase also catalyzes dephosphorylation of GC-A, and this is directly correlated with decreases in ANP-stimulatable guanylyl cyclase activity. Okadaic acid, an inhibitor of protein phosphatase 2A, blocks both the dephosphorylation and the desensitization. Therefore, in contrast to many other cell surface receptors, GC-A is desensitized by ligand-induced dephosphorylation.
心房利钠肽（ANP）与存在于肾脏和肾上腺等组织中的鸟苷酸环化酶-A（GC-A）受体结合，导致细胞内信号分子环磷酸鸟苷（cGMP）显著升高。在此，当在人胚胎293细胞中表达时，GC-A被证明以磷酸化蛋白的形式存在。32P主要与磷酸丝氨酸相关，只有微量的磷酸苏氨酸。ANP的添加导致受体的时间依赖性去磷酸化以及脱敏，这并非由于ANP介导的受体蛋白量的减少。用ANP处理细胞后，GC-A在十二烷基硫酸钠-聚丙烯酰胺凝胶电泳上的迁移率增加，并且蛋白磷酸酶2A诱导相同的迁移率变化。该蛋白磷酸酶还催化GC-A的去磷酸化，这与ANP刺激的鸟苷酸环化酶活性的降低直接相关。蛋白磷酸酶2A的抑制剂冈田酸可阻断去磷酸化和脱敏。因此，与许多其他细胞表面受体不同，GC-A通过配体诱导的去磷酸化而脱敏。
