Selectivity of lynx proteins on insect nicotinic acetylcholine receptors in the brown planthopper, Nilaparvata lugens.

Neuronal nicotinic acetylcholine receptors (nAChRs) are major excitatory neurotransmitter receptors in both vertebrates and invertebrates. Two lynx proteins (Nl-lynx1 and Nl-lynx2) have been identified in the brown planthopper, Nilaparvata lugens, which act as modulators on insect nAChRs. In the present study, two lynx proteins were found to act on the triplet receptor Nlalpha1/Nlalpha2/beta2 expressed in Xenopus oocytes, increasing agonist-evoked macroscopic currents, but not changing agonist sensitivity and desensitization properties. Nl-lynx1 and Nl-lynx2 increased I(max) (maximum responses) of acetylcholine to 4.85-fold and 2.40-fold of that of Nlalpha1/Nlalpha2/beta2 alone, and they also increased I(max) of imidacloprid to 2.57-fold and 1.25-fold. Although, on another triplet nAChRs Nlalpha3/Nlalpha8/beta2, Nl-lynx2 increased I(max) of acetylcholine and imidacloprid to 3.63-fold and 2.16-fold, Nl-lynx1 had no effects on I(max) of either acetylcholine or imidacloprid. The results demonstrate the selectivity of lynx proteins for different insect nAChR subtypes. This selectivity was also identified in native N. Lugens. Co-immunoprecipitation was found between Nlalpha1/Nlalpha2-containing receptors and both Nl-lynx1 and Nl-lynx2, but was only found between Nlalpha3/Nlalpha8-containing receptors and Nl-lynx2. When the previously identified Nlalpha1(Y151S) and Nlalpha3(Y151S) mutations were included (Nlalpha1(Y151S)/Nlalpha2/beta2 and Nlalpha3(Y151S)/Nlalpha8/beta2), the increase in I(max) of imidacloprid, but not acetylcholine, caused by co-expression of Nl-lynx1 and Nl-lynx2 was more noticeable than that of their wildtype counterparts. Taken together, these data suggest that two modulators, Nl-lynx1 and Nl-lynx2, might serve as an influencing factor in target site insensitivity in N. lugens, such as Y151S mutation.