Differential expression of SNMP-1 and SNMP-2 proteins in pheromone-sensitive hairs of moths

In moths the detection of female-released sex pheromones involves hairlike structures on the male antenna. These long sensilla trichodea usually contain 2-3 chemosensory neurons accompanied by several supporting cells. Previous studies have shown that the pheromone-specific neurons are characterized by a "sensory neuron membrane protein" (SNMP) which is homologous to the CD36 family and localized in the dendrite membrane. By employing the SNMP-2 sequence from Manduca sexta we have isolated cDNAs that encode SNMP-2 proteins from Heliothis virescens (HvirSNMP-2) and Antheraea polyphemus (ApolSNMP-2). To elucidate the topographic and cell type-specific expression of these SNMP subtypes, 2-color in situ hybridization experiments were performed with tissue sections through the male antennae. For H. virescens, a specific probe for the pheromone receptor HR13 was used to identify pheromone-responsive neurons. It was found that HvirSNMP-1 and HR13 were coexpressed in the same cells; in contrast, HvirSNMP-2 was not expressed in HR13 cells but rather in cells that surrounded the HR13 neurons, apparently the supporting cells. A corresponding expression pattern was also found for ApolSNMP-1 and ApolSNMP-2 on the antenna of male A. polyphemus. Our results indicate that SNMP-1s and SNMP-2s are differentially expressed in cells of pheromone-sensitive sensilla and suggest distinct functions for the 2 SNMP subtypes in the olfactory system.