Coupling of M3 Acetylcholine Receptor to Gq16 Activates a Natriuretic Peptide Receptor Guanylyl Cyclase

Muscarinic activation of tracheal smooth muscle (TSM) involves a M₃AChR/heterotrimeric-G protein/NPR-GC coupling mechanism. G protein activators Mastoparan (MAS) and Mastoparan-7 stimulated 4- and 10-fold the NPR-GC respectively, being insensitive to PTX and antibodies against Gα_i/o subfamily. Muscarinic and MAS stimulation of NPR-GC was blocked by antibodies against C-terminal of Gα_q16, whose expression was confirmed by RT-PCR. However, synthetic peptides from C-terminal of Gα_q15/16 stimulated the NPR-GC. Coupling of α_q16 to M₃AChR is supported by MAS decreased [³H]QNB binding, being abolished after M₃AChR-4-DAMP-alkylation. Anti-i₃M₃AChR antibodies blocked the muscarinic activation of NPR-GC, and synthetic peptide from i₃M₃AChR (M₃P) was more potent than MAS increasing GTPγ [³⁵S] and decreasing the [³H]QNB activities. Coupling between NPR-GC and Gα_q16 was evaluated by using trypsin-solubilized-fraction from TSM membranes, which displayed a MAS-sensitive-NPR-GC activity, being immunoprecipitated with anti-Gα_q16, also showing an immunoreactive heterotrimeric-G-β -subunit. These data support the existence of a novel transducing cascade, involving Gα_q16β γ coupling M₃AChR to NPR-GC.     

Phylogenetic patterns in larval host plant and ant association of Indo-Australian Arhopalini butterflies (Lycaenidae: Theclinae)

The Oriental butterfly genus Arhopala is by far the most species‐rich genus within the subfamily Theclinae. We investigated whether biotic interactions with larval host plants or ants are phylogenetically constrained in the evolutionary history of Arhopala, by collating available information on the ecology of Arhopala from the literature as well as from personal observations, and analysing and interpreting these data rigorously in a phylogenetic context. Larvae of all species in the sister‐group of Arhopala and Flos feed on Fabaceae. However, the predominant feeding preference of Arhopala s.l., with the exception of a particular monophyletic and species‐rich group, called ‘Group A’, appears to be centred on Fagaceae, with additional records of Dipterocarpaceae feeding. The preference for Fagaceae has strong phylogenetic inertia, as indicated by T‐PTP tests designed to test for phylogenetic signal. Adding all available life‐history data, using the phylogeny presented before as scaffolding, further increased the phylogenetic signal in host plant data. Feeding on Fabaceae (mainly in the outgroup) and Euphorbiaceae also showed significant phylogenetic signal, but feeding on Dipterocarpaceae did not and was found scattered across the phylogeny. Except for the Dipterocarpaceae, phylogenetic signal in feeding preferences was very clear, even despite uneven taxon sampling and apparent lability in host plant use. Ant association also demonstrated historical constraint, but based on the phylogenetic hypothesis presented here it was not clear whether increased ant association intimacy emerged independently various times in Group A, as well as in several basal groups. Our finding of distinct phylogenetic patterns in the host plant and to a lesser degree in ant association data contradicts the hypothesis that life‐history traits are very labile in the Lycaenidae. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society, 2005, 84 , 225–241.