Department of Internal Medicine, University of Kansas Medical Center, Kansas City, KS 66160-3018, USA.
Am J Physiol Renal Physiol. 2012 Nov 15;303(10):F1412-24. doi: 10.1152/ajprenal.00692.2011. Epub 2012 Sep 5.
In autosomal dominant polycystic kidney disease (ADPKD), binding of AVP to the V2 receptor (V2R) increases cAMP and accelerates cyst growth by stimulating cell proliferation and Cl(-)-dependent fluid secretion. Basal cAMP is elevated in human ADPKD cells compared with normal human kidney (NHK) cells. V2R mRNA levels are elevated in ADPKD cells; however, AVP caused a greater increase in global cAMP in NHK cells, suggesting an intrinsic difference in cAMP regulation. Expression, regulatory properties, and receptor coupling of specific adenylyl cyclases (ACs) provide temporal and spatial regulation of the cAMP signal. ADPKD and NHK cells express mRNAs for all nine ACs. Ca(2+)-inhibited ACs 5 and 6 are increased in ADPKD cells, while Ca(2+)/CaM-stimulated ACs 1 and 3 are downregulated. ACs 1, 3, 5, and 6 were detected in cyst cells in situ, and codistribution with aquaporin-2 suggests that these cysts were derived from collecting ducts. To determine the contribution of CaM-sensitive ACs to AVP signaling, cells were treated with W-7, a CaM inhibitor. W-7 decreased AVP-induced cAMP production and Cl(-) secretion by ADPKD cells. CaMKII inhibition increased AVP-induced cAMP, suggesting that cAMP synthesis is mediated by AC3. In contrast, CaM and CaMKII inhibition in NHK cells did not affect AVP-induced cAMP production. Restriction of intracellular Ca(2+) switched the response in NHK cells, such that CaM inhibition decreased AVP-induced cAMP production. We suggest that a compensatory response to decreased Ca(2+) in ADPKD cells switches V2R coupling from Ca(2+)-inhibited ACs 5/6 to Ca(2+)/CaM-stimulated AC3, to mitigate high cAMP levels in response to continuous AVP stimulation.
在常染色体显性多囊肾病 (ADPKD) 中，血管加压素 (AVP) 与 V2 受体 (V2R) 的结合会增加 cAMP，并通过刺激细胞增殖和 Cl(-)依赖性液体分泌来加速囊肿生长。与正常人类肾脏 (NHK) 细胞相比，人类 ADPKD 细胞中的基础 cAMP 升高。ADPKD 细胞中的 V2R mRNA 水平升高；然而，AVP 引起 NHK 细胞中环磷酸腺苷 (cAMP) 的增加幅度更大，这表明 cAMP 调节存在内在差异。特定腺苷酸环化酶 (AC) 的表达、调节特性和受体偶联为 cAMP 信号提供了时间和空间调节。ADPKD 和 NHK 细胞表达所有九种 AC 的 mRNA。ADPKD 细胞中 Ca(2+)-抑制的 AC5 和 AC6 增加，而 Ca(2+)/CaM 刺激的 AC1 和 AC3 下调。AC1、AC3、AC5 和 AC6 在原位囊肿细胞中被检测到，并且与水通道蛋白-2 共定位表明这些囊肿来自集合管。为了确定 CaM 敏感的 AC 对 AVP 信号的贡献，用 CaM 抑制剂 W-7 处理细胞。W-7 降低了 ADPKD 细胞中 AVP 诱导的 cAMP 产生和 Cl(-)分泌。CaMKII 抑制增加了 AVP 诱导的 cAMP，表明 cAMP 合成是由 AC3 介导的。相比之下，NHK 细胞中 CaM 和 CaMKII 抑制不影响 AVP 诱导的 cAMP 产生。细胞内 Ca(2+) 的限制使 NHK 细胞的反应发生转变，使得 CaM 抑制降低了 AVP 诱导的 cAMP 产生。我们认为，ADPKD 细胞中 Ca(2+) 的代偿性减少将 V2R 偶联从 Ca(2+)-抑制的 AC5/6 切换到 Ca(2+)/CaM 刺激的 AC3，以减轻对持续 AVP 刺激的高 cAMP 水平的反应。
