Reich G, Boekhoff I, Breer H, Ache B W
Whitney Laboratory, University of Florida, St. Augustine 32086, USA.
J Neurochem. 1999 Jul;73(1):147-52. doi: 10.1046/j.1471-4159.1999.0730147.x.
An elevated free Ca2+ concentration reduces odor-stimulated production of cyclic AMP (cAMP) in the outer dendritic membranes of lobster olfactory receptor neurons in vitro. This effect can occur within 50 ms of odor stimulation. The effect is concentration-dependent at submicromolar concentrations of free Ca2+. An elevated free Ca2+ concentration also reduces basal and forskolin-stimulated cAMP levels in a concentration-dependent manner, suggesting that Ca2+ is not targeting the activation of the odor receptor/G protein complex. The degradation of synthetic cAMP by phosphodiesterases is not enhanced by an increased free Ca2+ concentration, suggesting that Ca2+ acts by down-regulating the olfactory adenylyl cyclase. Western blot analysis of the lobster olfactory sensilla that contain the outer dendrites reveals a protein in the transduction zone with a molecular mass of approximately 138 kDa that is immunoreactive to an antiserum against adenylyl cyclase type III. Given earlier evidence that Ca2+ potentially enters the receptor cell through odor-activated inositol 1,4,5-trisphosphate-gated channels, our results suggest a possible route for cross talk between the cyclic nucleotide and the inositol phospholipid signaling pathways in lobster olfactory receptor neurons.
在体外，游离钙离子浓度升高会降低龙虾嗅觉受体神经元外树突膜中气味刺激引起的环磷酸腺苷（cAMP）生成。这种效应可在气味刺激后50毫秒内出现。在游离钙离子亚微摩尔浓度下，该效应呈浓度依赖性。游离钙离子浓度升高还会以浓度依赖性方式降低基础cAMP水平以及福斯高林刺激后的cAMP水平，这表明钙离子并非作用于气味受体/G蛋白复合物的激活过程。游离钙离子浓度升高并不会增强磷酸二酯酶对合成cAMP的降解作用，这表明钙离子是通过下调嗅觉腺苷酸环化酶来发挥作用的。对含有外树突的龙虾嗅觉感受器进行蛋白质印迹分析，结果显示在转导区域有一个分子量约为138 kDa的蛋白质，它与抗III型腺苷酸环化酶抗血清发生免疫反应。鉴于早期有证据表明钙离子可能通过气味激活的肌醇1,4,5-三磷酸门控通道进入受体细胞，我们的研究结果提示了龙虾嗅觉受体神经元中环核苷酸信号通路与肌醇磷脂信号通路之间可能存在相互作用的途径。
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