The mouse receptor transporting protein RTP1S and the fly SNMP1 support the functional expression of the Drosophila odorant coreceptor Orco in mammalian culture cells

Abstract

BackgroundFunctional expression of vertebrate and insect odorant receptors (ORs) in mammalian culture cells is hampered by an incorrect trafficking of these proteins to the plasma membrane. Receptor transporting proteins (RTPs) have been found to enhance the activity of transfected mammalian ORs in several heterologous systems. New methodsWe co-transfected the Drosophila olfactory coreceptor (Orco) in HEK293 cells with a truncated form of the mouse RTP1 (RTP1S) or with the Drosophila sensory neuron membrane protein 1 (SNMP1), which is required for the detection of the pheromone cis-vaccenyl acetate and was shown to be apposed to Orco within the functional receptor unit. ResultsCo-transfection of Orco with either of the two constructs led to an enhanced response to stimulations with the synthetic Orco agonist VUAA1, as compared to transfection with Orco alone. Comparison with existing methodsThis method enhances the functional expression of Orco in HEK293 cells in comparison to conventional transfection with Orco alone and enables the use of a lower amount of Orco DNA for transfection. ConclusionMammalian RTPs can enhance the expression of insect ORs. Moreover, the ability of SNMP1 to mimic the RTP1S effect may indicate possible new roles of this protein apart from being involved in pheromone detection. These results provide researchers with a fast and inexpensive way to optimize the functional expression of insect ORs in heterologous systems and open the search for insect proteins analogous to mammalian RTPs.