André C, Erraji L, Gaston J, Grimber G, Briand P, Guillet J G
INSERM U380, Institut Cochin de Génétique Moléculaire, Université René Descartes, Paris, France.
Eur J Biochem. 1996 Oct 15;241(2):417-24. doi: 10.1111/j.1432-1033.1996.00417.x.
Up to now, transgenic mice models created to study the physiological impact of alterations in the human beta-adrenoceptor system have only focused on cardiac tissues and carried hybrid transgenes with strong cardiac promoters. We have developed a transgenic mouse strain (F28) carrying the human beta 2-adrenoceptor gene with its natural promoter region with the aim of producing a model that more closely reproduces the natural human beta 2-adrenoceptor tissue expression pattern. By means of northern blot analyses, using the appropriate probes, we have obtained evidence that (a) the human beta 2-adrenoceptor's structural gene is transcribed in several tissues of F28 mice; (b) the tissue distribution pattern of human beta 2-adrenoceptor mRNA in F28 mice completely differs from that of mouse beta 2-adrenoceptor mRNA; and (c) the tissue distribution pattern of mouse beta 2-adrenoceptor mRNA in F28 mice is very similar to that observed in their non-transgenic littermates. Like humans, F28 mice express human beta 2-adrenoceptor mRNA in liver, lung, brain, heart, and muscle. However, unlike humans, F28 mice do not accumulate human beta 2-adrenoceptor mRNA in kidney and spleen. By using [125I]iodocyanopindolol to label all beta-adrenoceptors and ICI 118,551 to discriminate between the binding to beta 2- and beta 1-adrenoceptors we have demonstrated that the beta 2-adrenoceptor binding activity increases over control values in F28 mouse tissues that accumulate transgenic mRNA. Accordingly, the number of beta 2-adrenoceptors increased slightly over the control values in muscle, heart, brain, and lung of F28 mice, while in liver these receptors were strongly overexpressed. We further showed that transgene beta 2-adrenoceptors couple to GTP-binding proteins, mediate beta-adrenoceptor agonist-stimulated adenylyl cyclase activation, and cause a strong enhancement of this response in liver membranes of F28 versus control mice. Finally, F28 mice show a phenotype of depressed ponderal development and perturbed hindquarter movements. This unique model should be useful to further investigate beta 2-adrenoceptor causal relationships with human pathologies.
到目前为止，为研究人类β-肾上腺素能受体系统改变的生理影响而创建的转基因小鼠模型仅关注心脏组织，并携带带有强心脏启动子的杂交转基因。我们已经开发出一种转基因小鼠品系（F28），其携带具有天然启动子区域的人类β2-肾上腺素能受体基因，目的是建立一个更能重现人类β2-肾上腺素能受体自然组织表达模式的模型。通过使用适当的探针进行Northern印迹分析，我们获得的证据表明：（a）人类β2-肾上腺素能受体的结构基因在F28小鼠的多个组织中被转录；（b）F28小鼠中人类β2-肾上腺素能受体mRNA的组织分布模式与小鼠β2-肾上腺素能受体mRNA的完全不同；（c）F28小鼠中小鼠β2-肾上腺素能受体mRNA的组织分布模式与其非转基因同窝小鼠中观察到的非常相似。与人类一样，F28小鼠在肝脏、肺、脑、心脏和肌肉中表达人类β2-肾上腺素能受体mRNA。然而，与人类不同的是，F28小鼠在肾脏和脾脏中不积累人类β2-肾上腺素能受体mRNA。通过使用[125I]碘氰吲哚洛尔标记所有β-肾上腺素能受体，并使用ICI-118,551区分与β2-和β1-肾上腺素能受体的结合，我们证明在积累转基因mRNA的F28小鼠组织中，β2-肾上腺素能受体结合活性相对于对照值增加。因此，F28小鼠的肌肉、心脏、脑和肺中β2-肾上腺素能受体的数量相对于对照值略有增加，而在肝脏中这些受体则强烈过表达。我们进一步表明，转基因β2-肾上腺素能受体与GTP结合蛋白偶联，介导β-肾上腺素能受体激动剂刺激的腺苷酸环化酶激活，并且与对照小鼠相比，F28小鼠肝细胞膜中的这种反应强烈增强。最后，F28小鼠表现出体重发育迟缓以及后肢运动紊乱的表型。这个独特的模型应该有助于进一步研究β2-肾上腺素能受体与人类疾病的因果关系。
