WAKE-mediated modulation of cVA perception via a hierarchical neuro-endocrine axis in Drosophila male-male courtship behaviour.

The nervous and endocrine systems coordinate with each other to closely influence physiological and behavioural responses in animals. Here we show that WAKE (encoded by wide awake, also known as wake) modulates membrane levels of GABAA receptor Resistance to Dieldrin (Rdl), in insulin-producing cells of adult male Drosophila melanogaster. This results in changes to secretion of insulin-like peptides which is associated with changes in juvenile hormone biosynthesis in the corpus allatum, which in turn leads to a decrease in 20-hydroxyecdysone levels. A reduction in ecdysone signalling changes neural architecture and lowers the perception of the male-specific sex pheromone 11-cis-vaccenyl acetate by odorant receptor 67d olfactory neurons. These finding explain why WAKE-deficient in Drosophila elicits significant male-male courtship behaviour.

Isomeric triazines exhibit unique profiles of bioorthogonal reactivity.

Expanding the scope of bioorthogonal reactivity requires access to new and mutually compatible reagents. We report here that 1,2,4-triazines can be tuned to exhibit unique reaction profiles with biocompatible strained alkenes and alkynes. Computational analyses were used to identify candidate orthogonal reactions, and the predictions were experimentally verified. Notably, 5-substituted triazines, unlike their 6-substituted counterparts, undergo rapid [4 + 2] cycloadditions with a sterically encumbered strained alkyne. This unique, sterically controlled reactivity was exploited for dual bioorthogonal labeling. Mutually orthogonal triazines and cycloaddition chemistries will enable new multi-component imaging applications.

Cyclopropenones for Metabolic Targeting and Sequential Bioorthogonal Labeling.

Cyclopropenones are attractive motifs for bioorthogonal chemistry, owing to their small size and unique modes of reactivity. Unfortunately, the fastest-reacting cyclopropenones are insufficiently stable for routine intracellular use. Here we report cyclopropenones with improved stability that maintain robust reactivity with bioorthogonal phosphines. Functionalized cyclopropenones were synthesized and their lifetimes in aqueous media and cellular environments were analyzed. The most robust cyclopropenones were further treated with a panel of phosphine probes, and reaction rates were measured. Two of the phosphine scaffolds afforded ∼100-fold rate enhancements compared to previously reported reagents. Importantly, the stabilized cyclopropenones were suitable for recombinant protein production via genetic code expansion. The products of the cyclopropenone ligation were also amenable to traceless Staudinger ligations, setting the stage for tandem labeling experiments.

A Bioorthogonal Ligation of Cyclopropenones Mediated by Triarylphosphines.

Bioorthogonal chemistries have been widely used to probe biopolymers in living systems. To date, though, only a handful of broadly useful transformations have been identified because of the stringent requirements placed on the reactants. Here we report a novel bioorthogonal ligation between cyclopropenones and functionalized phosphines. These components are stable in physiological buffers and react rapidly with one another to form covalent adducts. The cyclopropenone ligation is also distinct from other bioorthogonal chemistries in that it makes use of readily accessible, commercially available reagents and proceeds via a nucleophilic reaction pathway. On the basis of these features, the cyclopropenone ligation is poised to join the ranks of chemistries with utility in living systems.

Building better bioorthogonal reactions.

Over the past two decades, there has been intense interest in designing and implementing selective (bioorthogonal) reactions for biomolecule tracking. Here we review the most widely used bioorthogonal chemistries in live cells and animals, drawing particular attention to the unique functional groups underlying these transformations. We also describe recent efforts to tune functional group reactivities and stabilities to access even more rapid and selective chemistries. Last, we highlight ongoing challenges in identifying new bioorthogonal reagents and combinations of reactions that can be used concurrently to tag multiple biomolecules.

Isomeric cyclopropenes exhibit unique bioorthogonal reactivities.

Bioorthogonal chemistries have provided tremendous insight into biomolecule structure and function. However, many popular bioorthogonal transformations are incompatible with one another, limiting their utility for studies of multiple biomolecules in tandem. We identified two reactions that can be used concurrently to tag biomolecules in complex environments: the inverse electron-demand Diels-Alder reaction of tetrazines with 1,3-disubstituted cyclopropenes, and the 1,3-dipolar cycloaddition of nitrile imines with 3,3-disubstituted cyclopropenes. Remarkably, the cyclopropenes used in these transformations differ by the placement of a single methyl group. Such orthogonally reactive scaffolds will bolster efforts to monitor multicomponent processes in cells and organisms.

Enantioselective α-benzylation of aldehydes via photoredox organocatalysis.

The first enantioselective aldehyde α-benzylation using electron-deficient aryl and heteroaryl substrates has been accomplished. The productive merger of a chiral imidazolidinone organocatalyst and a commercially available iridium photoredox catalyst in the presence of household fluorescent light directly affords the desired homobenzylic stereogenicity in good to excellent yield and enantioselectivity. The utility of this methodology has been demonstrated via rapid access to an enantioenriched drug target for angiogenesis suppression.

Asymmetric Mannich reactions with in situ generation of carbamate-protected imines by an organic catalyst.

The instability of carbamate-protected alkyl imines has greatly hampered the development of catalytic asymmetric Mannich reactions suitable for the synthesis of optically active carbamate-protected chiral alkyl amines. A highly enantioselective Mannich reaction with in situ generation of carbamate-protected imines from stable alpha-amido sulfones catalyzed by an organic catalyst was developed. This reaction provides a concise and highly enantioselective route converting aromatic and aliphatic aldehydes into optically active aryl and alkyl beta-amino acids. [reaction: see text].

Inhibition of hypoxia-induced calcium responses in pulmonary arterial smooth muscle by acetazolamide is independent of carbonic anhydrase inhibition.

Hypoxic pulmonary vasoconstriction (HPV) occurs with ascent to high altitude and can contribute to development of high altitude pulmonary edema (HAPE). Vascular smooth muscle contains carbonic anhydrase (CA), and acetazolamide (AZ), a CA inhibitor, blunts HPV and might be useful in the prevention of HAPE. The mechanism by which AZ impairs HPV is uncertain. Originally developed as a diuretic, AZ also has direct effects on systemic vascular smooth muscle, including modulation of pH and membrane potential; however, the effect of AZ on pulmonary arterial smooth muscle cells (PASMCs) is unknown. Since HPV requires Ca2+ influx into PASMCs and can be modulated by pH, we hypothesized that AZ alters hypoxia-induced changes in PASMC intracellular pH (pH(i)) or Ca2+ concentration ([Ca2+](i)). Using fluorescent microscopy, we tested the effect of AZ as well as two other potent CA inhibitors, benzolamide and ethoxzolamide, which exhibit low and high membrane permeability, respectively, on hypoxia-induced responses in PASMCs. Hypoxia caused a significant increase in [Ca2+](i) but no change in pH(i). All three CA inhibitors slightly decreased basal pH(i), but only AZ caused a concentration-dependent decrease in the [Ca2+](i) response to hypoxia. AZ had no effect on the KCl-induced increase in [Ca2+](i) or membrane potential. N-methyl-AZ, a synthesized compound lacking the unsubstituted sulfonamide group required for CA inhibition, had no effect on pH(i) but inhibited hypoxia-induced Ca2+ responses. These results suggest that AZ attenuates HPV by selectively inhibiting hypoxia-induced Ca2+ responses via a mechanism independent of CA inhibition, changes in pH(i), or membrane potential.