Nesic, D. | bioRxiv Science

bioRxiv2026

The structural logic of insect olfactory receptor assembly and gating

Insects detect the chemical world using a large family of odorant-gated ion channels, each formed from a variable odorant-binding subunit (OR) and a single conserved co-receptor Orco. This modular organization is thought to allow tuning ORs to diversify their chemical recognition while Orco provides structural stability to the heteromer. Yet Orco can be autonomously activated by synthetic agonists, suggesting that it may contribute to channel gating rather than serving solely as a structural scaffold. Here, we combine cryo-electron microscopy with analyses of receptor stoichiometry and function to define the structural logic underlying Orco-OR assembly and gating. We show that Orco retains the canonical ligand-binding pocket of ORs but is chemically insulated from environmental odorants by a phospholipid that occupies this site. The Orco agonist VUAA4 instead binds a membrane-accessible crevice adjacent to the gate, defining a distinct site of allosteric modulation. We further demonstrate that Orco-OR heteromers can assemble in multiple stoichiometries through shape complementarity within the intracellular anchor domain and resolve structures with both a 3:1 and 2:2 architecture. Receptors constrained to a 2:2 stoichiometry are functional but productive gating requires cooperative engagement of multiple subunits within the heteromer. Comparison with the distinct gating states of a basal homomeric olfactory receptor suggests that existing Orco-OR structures capture nonconductive intermediates within the broader conformational landscape of this receptor family. Together, these findings suggest how Orco can flexibly assemble and function with highly divergent ORs, acting not simply as a structural scaffold but as an integral partner in cooperative channel gating, thereby enabling the extraordinary diversification of insect olfactory receptors.

neuroscience↗

bioRxiv2019

Novel Pure αVβ3 Integrin Antagonists That Do Not Induce Receptor Extension, Prime the Receptor, or Enhance Angiogenesis at Low Concentrations

The integrin V{beta}3 receptor has been implicated in several important diseases, but no V{beta}3 antagonists are approved for human therapy. One possible limitation of current small-molecule antagonists is their ability to induce a major conformational change in the receptor that induces it to adopt a high-affinity ligand-binding state. In response, we used structural inferences from a pure peptide antagonist to design the small-molecule pure antagonists TDI-4161 and TDI-3761. Both compounds inhibit V{beta}3-mediated cell adhesion to V{beta}3 ligands, but do not induce the conformational change as judged by antibody binding, electron microscopy, X-ray crystallography, and receptor priming studies. Both compounds demonstrated the favorable property of inhibiting bone resorption in vitro, supporting potential value in treating osteoporosis. Neither, however, had the unfavorable property of the V{beta}3 antagonist cilengitide of paradoxically enhancing aortic sprout angiogenesis at concentrations below its IC50, which correlates with cilengitides enhancement of tumor growth in vivo.\n\nSignificance StatementV{beta}3 is a potential therapeutic target for several important human diseases, but there are currently no V{beta}3 antagonists approved for human therapy. Current candidates are primarily based on the Arg-Gly-Asp (RGD) motif and act as partial agonists in that they induce V{beta}3 to undergo a conformational change that converts it into a high-affinity ligand-binding state. We have used structure-guided design to produce pure small-molecule V{beta}3 antagonists that do not induce the conformational change as judged by protein crystallography, electron microscopy, and receptor priming. These compounds inhibit V{beta}3-mediated bone resorption in vitro, but unlike the partial agonist cilengitide, do not enhance angiogenesis at low doses, a property that correlates with low-dose cilengitides enhancement of tumor growth in vivo. These pure V{beta}3 antagonists can help define V{beta}3s role in animal models. If they demonstrate benefits over partial agonists in these model systems, they may be appropriate to consider for human therapy.

pharmacology and toxicology↗