Search

In recent years, delivery systems based on the incorporation of thiols/disulfides have been extensively explored to promote the intracellular delivery of biological cargoes. However, it remains unclear about the detailed processes of thiol-disulfide exchanges taking place on the cell surface and how the exchange reactions promote the cellular uptake of cargoes bearing thiols or disulfide bonds. In this work, we report the rational design of biscysteine motif-containing peptide probes with substantially different ring-closing property and how these peptide probes were employed to explore the thiol-disulfide exchanges on the cell surface. Our results show that extensive thiol-disulfide exchanges between peptides and exofacial protein thiols/disulfides are involved in the cellular uptake of these peptide probes, and importantly glutathione (GSH) exported from the cytosols participates extensively in the exchange reactions. Cysteine-glycine-cysteine (CGC)-containing peptide probes can be more efficiently taken up by cells compared to other probes, and we suggested that the driving force for the superior cellular uptake arises from very likely the unique propensity of the CGC motif in forming doubly bridged disulfide bonds with exofacial proteins. Our probe-based strategy provides firsthand information on the detailed processes of the exchange reactions, which would be of great benefit to the development of delivery systems based on the extracellular thiol-disulfide exchanges for intracellular delivery of biologics.

SIRT1 is an important protein that catalyzes the nicotinamide adenine dinucleotide (NAD)(+)-dependent deacetylation reaction, which is regarded as a novel target to treat metabolic disorders and aging-related diseases. However, there is lack of appropriate approach for SIRT1 modulator screening and bioimaging of SIRT1 in living cells. We designed and synthesized a "turn-on" fluorescent probe by connecting a specifically recognized peptide to tetraphenylethene core. It exhibits excellent selectivity and sensitivity in homogeneous measurement of SIRT1 activity for screening both SIRT1 inhibitors and activators. 20(S)-ginsenoside Rg3 and ophiopogonin D' were found to activate SIRT1. It was also successfully applied to monitor SIRT1 modulation in the cardiomyocytes as well as in the wild-type and SIRT1(-/-) mesenchymal stem cells.