Gupta G, Azam M, Yang L, Danziger R S
Department of Medicine, College of Physicians and Surgeons of Columbia University, New York, New York 10032, USA.
J Clin Invest. 1997 Sep 15;100(6):1488-92. doi: 10.1172/JCI119670.
Cytosolic guanylyl cyclases (GTP pyrophosphate-lyase [cyclizing; EC 4.6.1.2]), primary receptors for nitric oxide (NO) generated by NO synthases, are obligate heterodimers consisting of an alpha and a beta subunit. The alpha1/beta1 form of guanylyl cyclase has the greatest activity and is considered the universal form. An isomer of the beta1 subunit, i.e., beta2, has been detected in the liver and kidney, however, its role is not known. In this study, we investigated the function of beta2. Immunoprecipitation experiments showed that the beta2 subunit forms a heterodimer with the alpha1 subunit. NO-stimulated cGMP formation in COS 7 cells cotransfected with the alpha1 and beta2 subunits was approximately 1/3 of that when alpha1 and beta1 subunits were cotransfected. The beta2 subunit inhibited NO-stimulated activity of the alpha1/beta1 form of guanylyl cyclase and NO-stimulated cGMP formation in cultured smooth muscle cells. Our results provide the first evidence that the beta2 subunit can regulate NO sensitivity of the alpha1/beta1 form of guanylyl cyclase. Northern analysis for guanylyl cyclase subunits was performed on RNA from kidneys of Dahl salt-sensitive rats, which have been shown to have decreased renal sensitivity to NO. Compared to the Dahl salt-resistant rat, message for beta2 was increased, beta1 was decreased, and alpha1 was unchanged. These results suggest a molecular basis for decreased renal guanylyl cyclase activity, i.e. , an increase in the alpha1/beta2 heterodimer, and decrease in the alpha1/beta1 heterodimer.
胞质型鸟苷酸环化酶（GTP焦磷酸裂解酶[环化；EC 4.6.1.2]）是一氧化氮合酶产生的一氧化氮（NO）的主要受体，是由一个α亚基和一个β亚基组成的 obligate 异二聚体。鸟苷酸环化酶的α1/β1形式具有最大活性，被认为是普遍形式。然而，在肝脏和肾脏中检测到了β1亚基的一种异构体，即β2，但其作用尚不清楚。在本研究中，我们研究了β2的功能。免疫沉淀实验表明，β2亚基与α1亚基形成异二聚体。与共转染α1和β1亚基时相比，在共转染α1和β2亚基的COS 7细胞中，NO刺激的cGMP形成约为其三分之一。β2亚基抑制培养的平滑肌细胞中鸟苷酸环化酶α1/β1形式的NO刺激活性和NO刺激的cGMP形成。我们的结果提供了首个证据，即β2亚基可调节鸟苷酸环化酶α1/β1形式的NO敏感性。对 Dahl 盐敏感大鼠肾脏的RNA进行了鸟苷酸环化酶亚基的Northern分析，这些大鼠已被证明对NO的肾脏敏感性降低。与Dahl盐抵抗大鼠相比，β2的信使RNA增加，β1减少，α1不变。这些结果提示了肾脏鸟苷酸环化酶活性降低的分子基础，即α1/β2异二聚体增加，α1/β1异二聚体减少。
