Lidow M S, Roberts A, Zhang L, Koh P O, Lezcano N, Bergson C
Department of Oral and Craniofacial Biological Sciences and Program in Neuroscience, University of Maryland, 5-A-12, HHH 666 W. Baltimore St., Baltimore, MD 21201, USA.
Eur J Pharmacol. 2001 Sep 21;427(3):187-93. doi: 10.1016/s0014-2999(01)01265-1.
The recently cloned protein, calcyon, potentiates crosstalk between G(s)-coupled dopamine D1 receptors and heterologous G(q/11)-coupled receptors allowing dopamine D1 receptors to stimulate intracellular Ca(2+) release, in addition to cAMP production. This crosstalk also requires the participating G(q/11)-coupled receptors to be primed by their agonists. We examined the ability of calcyon and priming to regulate the affinity of dopamine D1 receptors for its ligands. Receptor binding assays were performed on HEK293 cell membrane preparations expressing dopamine D1 receptors either alone or in combination with calcyon. Co-expression of dopamine D1 receptor and calcyon affected neither the affinity of this receptor for antagonists nor the affinity of agonist binding to this receptor high and low-affinity states. However, the presence of calcyon dramatically decreased the proportion of the high-affinity dopamine D1 receptor agonist binding sites. This decrease was reversed by carbachol, which primes the receptor crosstalk by stimulating endogenous G(q/11)-coupled muscarinic receptors. Our findings suggest that calcyon regulates the ability of dopamine D1 receptors to achieve the high-affinity state for agonists, in a manner that depends on priming of receptor crosstalk.
最近克隆出的蛋白钙调素，可增强G(s)偶联的多巴胺D1受体与异源G(q/11)偶联受体之间的串扰，使多巴胺D1受体除了能产生环磷酸腺苷（cAMP）外，还能刺激细胞内钙离子（Ca(2+)）释放。这种串扰还要求参与的G(q/11)偶联受体由其激动剂引发。我们研究了钙调素和引发作用对多巴胺D1受体与其配体亲和力的调节能力。在单独表达多巴胺D1受体或与钙调素共同表达的HEK293细胞膜制剂上进行受体结合试验。多巴胺D1受体与钙调素的共同表达既不影响该受体与拮抗剂的亲和力，也不影响激动剂与该受体高亲和力和低亲和力状态结合的亲和力。然而，钙调素的存在显著降低了高亲和力多巴胺D1受体激动剂结合位点的比例。这种降低可被卡巴胆碱逆转，卡巴胆碱通过刺激内源性G(q/11)偶联的毒蕈碱受体引发受体串扰。我们的研究结果表明，钙调素以一种依赖于受体串扰引发的方式调节多巴胺D1受体达到激动剂高亲和力状态的能力。
