Li Zhengzheng, Ni Jinfei D, Huang Jia, Montell Craig
Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America.
Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America; Neuroscience Research Institute and Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, California.
PLoS Genet. 2014 Sep 25;10(9):e1004600. doi: 10.1371/journal.pgen.1004600. eCollection 2014 Sep.
Pheromones are used for conspecific communication by many animals. In Drosophila, the volatile male-specific pheromone 11-cis vaccenyl acetate (cVA) supplies an important signal for gender recognition. Sensing of cVA by the olfactory system depends on multiple components, including an olfactory receptor (OR67d), the co-receptor ORCO, and an odorant binding protein (LUSH). In addition, a CD36 related protein, sensory neuron membrane protein 1 (SNMP1) is also involved in cVA detection. Loss of SNMP1 has been reported to eliminate cVA responsiveness, and to greatly increase spontaneous activity of OR67d-expressing olfactory receptor neurons (ORNs). Here, we found the snmp1(1) mutation did not abolish cVA responsiveness or cause high spontaneous activity. The cVA responses in snmp1 mutants displayed a delayed onset, and took longer to reach peak activity than wild-type. Most strikingly, loss of SNMP1 caused a dramatic delay in signal termination. The profound impairment in signal inactivation accounted for the previously reported "spontaneous activity," which represented continuous activation following transient exposure to environmental cVA. We introduced the silk moth receptor (BmOR1) in OR67d ORNs of snmp1(1) flies and found that the ORNs showed slow activation and deactivation kinetics in response to the BmOR1 ligand (bombykol). We expressed the bombykol receptor complex in Xenopus oocytes in the presence or absence of the silk moth SNMP1 (BmSNMP) and found that addition of BmSNMP accelerated receptor activation and deactivation. Our results thus clarify SNMP1 as an important player required for the rapid kinetics of the pheromone response in insects.
信息素被许多动物用于种内交流。在果蝇中，挥发性的雄性特异性信息素11-顺式乙酸vaccenyl酯（cVA）为性别识别提供了重要信号。嗅觉系统对cVA的感知取决于多个组件，包括一种嗅觉受体（OR67d）、共同受体ORCO和一种气味结合蛋白（LUSH）。此外，一种与CD36相关的蛋白，感觉神经元膜蛋白1（SNMP1）也参与cVA检测。据报道，SNMP1的缺失会消除cVA反应性，并大幅增加表达OR67d的嗅觉受体神经元（ORN）的自发活动。在这里，我们发现snmp1(1)突变并没有消除cVA反应性或导致高自发活动。snmp1突变体中的cVA反应表现出延迟发作，达到峰值活动的时间比野生型更长。最引人注目的是，SNMP1的缺失导致信号终止出现显著延迟。信号失活的严重受损解释了先前报道的“自发活动”，这代表了在短暂暴露于环境cVA后持续的激活。我们在snmp1(1)果蝇的OR67d ORN中引入了家蚕受体（BmOR1），发现ORN对BmOR1配体（蚕蛾醇）的反应显示出缓慢的激活和失活动力学。我们在有或没有家蚕SNMP1（BmSNMP）的情况下，在家爪蟾卵母细胞中表达蚕蛾醇受体复合物，发现添加BmSNMP会加速受体的激活和失活。因此，我们的结果阐明了SNMP1是昆虫信息素反应快速动力学所需的重要参与者。
