Antennal SNMPs (sensor neuron membrane proteins) of lepidoptera define a unique family of invertebrate CD36-like proteins

SNMP1-Apol is an antennal-specific protein of the wild silk moth Antheraea polyphemus; the protein Is abundantly expressed and localized to the recept or membranes of sex-pheromone specific olfactory sensory neurons (OSNs). SN MP1-Apol is thought to function in odor detection based on its olfactory-sp ecific expression, localization within OSNs, developmental time of expressi on, and apparent homology to the CD36 family of membrane-bound receptor pro teins. In the current study, SNMP1-Apol homologues were identified from the moths Bombyx mori, Heliothis virescens, and Manduca sexta. These species p osses antennal mRNAs encoding proteins with amino acid sequence identities ranging from 75-80%; these proteins are collectively designated SNMP1. A se cond AL sexta SNMP homologue, previously identified and partially sequenced [Robertson et al.: Insect Mol Biol 8:501-518, 1999] was fully sequenced an d characterized. The encoded protein shares only 26-27% sequence identity w ith the SNMP1 proteins, and is thus designated SNMP2-Msex. The SNMP sequenc es were used to identify 14 and four possible homologues in Drosophila mela nogaster and Caenorhabditis elegans genome databases, respectively; thus, g reatly expanding CD36 family membership among the invertebrate lineages. De spite their sequence difference, SNMP1-Msex and SNMP2-Msex expression is lo calized to OSNs and occurs simultaneously with the onset of olfactory funct ion. These findings suggest that SNMPs play a central role in odor detectio n in insects, and that the CD36 gene family is widely represented among ani mal phyla. The SNMPs are the only identified neuronal members of the CD36 f amily, and as such expand the activities of this gene family into roles inf luencing brain function and behavioral action. (C) 2001 John Wiley & Sons, Inc.