Moon C, Sung Y K, Reddy R, Ronnett G V
Department of Neuroscience, The Johns Hopkins University, Baltimore, MD 21205, USA.
Proc Natl Acad Sci U S A. 1999 Dec 7;96(25):14605-10. doi: 10.1073/pnas.96.25.14605.
Although odorants are known to activate olfactory receptor neurons through cAMP, the long-term effects of odorant detection are not known. Our recent findings indicate that there is also a delayed and sustained cAMP response, with kinetics sufficient to mediate long-term cellular responses. This cAMP response is mediated by cGMP through activation of adenylyl cyclase by protein kinase G (PKG). Therefore, we investigated the ability of odorants to regulate gene expression in rat olfactory epithelium. The cAMP-responsive binding protein (CREB) is a well-characterized transcription factor regulated by cAMP. We examined CREB activity in rat olfactory epithelium and olfactory receptor neurons (ORNs) after stimulation with odorants. Odorants increased levels of phosphorylated CREB in olfactory epithelium in vivo, and this increase was localized to ORNs in vitro. Incubation with 8-bromo-cGMP or sodium nitroprusside, a guanylyl cyclase activator, also increased phosphorylated CREB. In vitro, cAMP-dependent protein kinase phosphorylated CREB. In contrast, PKG failed to phosphorylate CREB directly in vitro. Our results demonstrate that the delayed odorant-induced cAMP signal activates CREB, which in turn may modulate gene expression in ORNs. In addition, cGMP indirectly affects CREB activation. This effect of cGMP on CREB activity through cAMP provides another mechanism for the modulation of CREB.
虽然已知气味分子通过环磷酸腺苷（cAMP）激活嗅觉受体神经元，但气味分子检测的长期影响尚不清楚。我们最近的研究结果表明，还存在一种延迟且持续的cAMP反应，其动力学足以介导长期的细胞反应。这种cAMP反应是由环磷酸鸟苷（cGMP）通过蛋白激酶G（PKG）激活腺苷酸环化酶来介导的。因此，我们研究了气味分子调节大鼠嗅觉上皮中基因表达的能力。cAMP反应元件结合蛋白（CREB）是一种已被充分表征的受cAMP调节的转录因子。我们在用气味分子刺激后检测了大鼠嗅觉上皮和嗅觉受体神经元（ORN）中的CREB活性。气味分子在体内增加了嗅觉上皮中磷酸化CREB的水平，并且这种增加在体外定位于ORN。用8-溴-cGMP或鸟苷酸环化酶激活剂硝普钠孵育也增加了磷酸化CREB。在体外，cAMP依赖性蛋白激酶使CREB磷酸化。相比之下，PKG在体外不能直接使CREB磷酸化。我们的结果表明，气味分子诱导的延迟cAMP信号激活了CREB，这反过来可能调节ORN中的基因表达。此外，cGMP间接影响CREB的激活。cGMP通过cAMP对CREB活性的这种作用为调节CREB提供了另一种机制。
