Thibonnier M, Preston J A, Dulin N, Wilkins P L, Berti-Mattera L N, Mattera R
Department of Medicine, Case Western Reserve University School of Medicine and University Hospitals of Cleveland, Ohio 44106-4951, USA.
Endocrinology. 1997 Oct;138(10):4109-22. doi: 10.1210/endo.138.10.5432.
The vasopressin (AVP) V3 pituitary receptor (V3R) is a G protein-coupled corticotropic phenotypic marker that is overexpressed in ACTH-hypersecreting tumors. Studies of the agonist/antagonist binding profile and signal transduction pathways linked to the human V3R have been limited because of the scarcity of this protein. To define the signals activated by V3Rs and the eventual changes triggered by developmental or pathological receptor regulation, we developed Chinese hamster ovary (CHO)-V3 cells stably expressing low, medium, or high levels of human V3Rs (binding capacity, <10, 10-25, and 25-100 pmol/mg, respectively). The affinity of the V3R for 21 peptide and nonpeptide AVP analogs was clearly distinct from that exhibited by the human V1R and V2R. AVP triggered stimulation of phospholipase C in CHO-V3 cells (partially sensitive to treatment with pertussis toxin) with a potency directly proportional to receptor density. V3R-mediated arachidonic acid release also was also sensitive to pertussis toxin and more efficacious in cells exhibiting medium than in those with high receptor density. AVP also stimulated the pertussis toxin-insensitive uptake of [3H]thymidine in CHO-V3 cells. The concentration-response curves for this effect were monophasic in cells expressing low and medium levels of V3Rs; on the contrary, a biphasic curve was observed in cells with high V3R density. Coupling of V3R to increased production of cAMP was only observed in CHOV3 high cells, suggesting a negative relationship between increased cAMP production and DNA synthesis. Activation of mitogen-activated protein kinases by V3R was pertussis toxin insensitive, but was dependent on activation of phospholipase C and protein kinase C; both the level and duration of activation were a function of the receptor density. Thus, the human V3R has a pharmacological profile clearly distinct from that of the human V1R and V2R and activates several signaling pathways via different G proteins, depending on the level of receptor expression. The increased synthesis of DNA and cAMP levels observed in cells expressing medium and high levels of V3Rs, respectively, may represent important events in the tumorigenesis of corticotroph cells.
血管加压素（AVP）V3垂体受体（V3R）是一种G蛋白偶联的促肾上腺皮质激素表型标志物，在促肾上腺皮质激素分泌过多的肿瘤中过表达。由于这种蛋白质稀缺，对与人类V3R相关的激动剂/拮抗剂结合谱和信号转导途径的研究一直有限。为了确定V3R激活的信号以及发育或病理受体调节引发的最终变化，我们构建了稳定表达低、中、高水平人类V3R（结合能力分别为<10、10 - 25和25 - 100 pmol/mg）的中国仓鼠卵巢（CHO）-V3细胞。V3R对21种肽类和非肽类AVP类似物的亲和力明显不同于人类V1R和V2R。AVP在CHO-V3细胞中触发了磷脂酶C的刺激（对百日咳毒素处理部分敏感），其效力与受体密度成正比。V3R介导的花生四烯酸释放也对百日咳毒素敏感，并且在中等受体密度的细胞中比在高受体密度的细胞中更有效。AVP还刺激了CHO-V3细胞中对百日咳毒素不敏感的[3H]胸苷摄取。在表达低、中水平V3R的细胞中，这种效应的浓度-反应曲线是单相的；相反，在高V3R密度的细胞中观察到双相曲线。V3R与cAMP产生增加的偶联仅在CHOV3高表达细胞中观察到，这表明cAMP产生增加与DNA合成之间存在负相关。V3R对丝裂原活化蛋白激酶的激活对百日咳毒素不敏感，但依赖于磷脂酶C和蛋白激酶C的激活；激活的水平和持续时间都是受体密度的函数。因此，人类V3R具有与人类V1R和V2R明显不同的药理学特征，并通过不同的G蛋白激活多种信号通路，这取决于受体表达水平。在分别表达中、高水平V3R的细胞中观察到的DNA合成增加和cAMP水平升高，可能代表促肾上腺皮质激素细胞肿瘤发生中的重要事件。
