Immunodetection of Truncated Forms of the 6 Subunit of the nAChR in the Brain of Spinosad Resistant Ceratitis capitata Phenotypes

The alpha 6 subunit of the nicotinic acetylcholine receptor (nAChR) has been proposed as the target for spinosad in insects. Point mutations that result in premature stop codons in the alpha 6 gene of Ceratitis capitata flies have been previously associated with spinosad resistance, but it is unknown if these transcripts are translated and if so, what is the location of the putative truncated proteins. In this work, we produced a specific antibody against C. capitata alpha 6 (Cc alpha 6) and validated it by ELISA, Western blotting and immunofluorescence assays in brain tissues. The antibody detects both wild-type and truncated forms of Cc alpha 6 in vivo, and the protein is located in the cell membrane of the brain of wild-type spinosad sensitive flies. On the contrary, the shortened transcripts present in resistant flies generate putative truncated proteins that, for the most part, fail to reach their final destination in the membrane of the cells and remain in the cytoplasm. The differences observed in the locations of wild-type and truncated alpha 6 proteins are proposed to determine the susceptibility or resistance to spinosad.