Bao-Hui Zheng

Optogenetics is a powerful research approach that allows localized optical modulation of selected cells within an animal via the expression of genetically encoded photo-excitable ion channels. Commonly used optogenetic techniques rely on the expression of microbial opsin variants, which have many excellent features but suffer from various degrees of blue spectral overlap and limited channel conductance. Here, we expand the optogenetics toolbox in the form of a tunable, high-conductance vertebrate cation channel, zTrpa1b, coupled with photo-activated channel ligands, such as optovin and 4g6. Our results demonstrate that zTrpa1b/ligand pairing offers high light sensitivity, millisecond-scale response latency in vivo, as well as adjustable channel off latency. Exogenous in vivo expression of zTrpa1b in sensory neurons allowed subcellular photo-activation, enabling light-dependent motor control. zTrpa1b/ligand was also suitable for cardiomyocyte pacing, as shown in experiments performed on zebrafish hearts in vivo as well as in human stem cell-derived cardiomyocytes in vitro. Therefore, zTrpa1b/optovin represents a novel tool for flexible, high-conductance optogenetics.

Dynamic palmitoylation is an important post-translational modification regulating protein localization, trafficking, and signaling activities. The Asp-His-His-Cys (DHHC) domain containing enzymes are evolutionarily conserved palmitoyl acyltransferases (PATs) mediating diverse protein S-palmitoylation. Cerulenin is a natural product inhibitor of fatty acid biosynthesis and protein palmitoylation, through irreversible alkylation of the cysteine residues in the enzymes. Here, we report the synthesis and characterization of a “clickable” and long alkyl chain analogue of cerulenin as a chemical probe to investigate its cellular targets and to label and profile PATs in vitro and in live cells. Our results showed that the probe could stably label the DHHC-family PATs and enable mass spectrometry studies of PATs and other target proteins in the cellular proteome. Such probe provides a new chemical tool to dissect the functions of palmitoylating enzymes in cell signaling and diseases and reveals new cellular targets of the natural product cerulenin.

A Pd-catalyzed intramolecular asymmetric allylic alkylation (AAA) reaction with “hard” carbanions has been developed for the first time, affording 2,3-disubstituted indanones with high diastereo- and enantioselectivities. The transformation of these products into other core structures of natural products has been demonstrated.

Reversible S-palmitoylation is an important post-translational modification that regulates the trafficking, localization, and activity of proteins. Cysteine-rich Asp-His-His-Cys (DHHC) domain-containing enzymes are evolutionarily conserved protein palmitoyl acyltransferases (PATs). The human genome encodes 23 DHHC-PATs that regulate diverse cellular functions. Although chemical probes and proteomic methods to detect palmitoylated protein substrates have been reported, no probes for direct detection of the activity of PATs are available. Here we report the synthesis and characterization of 2-bromohexadec-15-ynoic acid and 2-bromooctadec-17-ynoic acid, which are analogues of 2-bromopalmitate (2-BP), as activity-based probes for PATs as well as other palmitoylating and 2-BP-binding enzymes. These probes will serve as new chemical tools for activity-based protein profiling to explore PATs, to dissect the functions of PATs in cell signaling and diseases, and to facilitate the identification of their inhibitors.

A new type of N-nucleophile has been developed in Pd-catalyzed asymmetric allylic amination with monosubstituted allyl substrates, affording corresponding branched allyl amines in high regio- and enantioselectivities. Either OMe or Boc group in products can be removed easily to provide primary amine derivatives with the optical purity unchanged.

The asymmetric catalytic synthesis of β-substituted tryptophan derivatives was realized in high diastereo- and enantioselectivity by the reaction of glycine derivatives with sulfonylindoles in the presence of catalyst derived from AgCl and a commercially available chiral monodentate phosphoramidite ligand. The resulting adduct was readily converted to β-substituted tryptophan in 95% overall yield for two steps, which presented a highly efficient route to chiral β-substituted tryptophan.

The kinetic resolution of indolines was realized via a Pd-catalyzed allylic substitution reaction by using Trost’s chiral ligand L10, affording optically active indolines and N-allylated indolines in high yields and high enantioselectivities with an S factor up to 59, which provided the first example for the kinetic resolution of nucleophiles via a transition-metal-catalyzed allylic substitution reaction.