2 research outputs found
Design, Synthesis, and Evaluation of a Diazirine Photoaffinity Probe for Ligand-Based Receptor Capture Targeting G Protein-Coupled Receptors.
Chemoproteomic approaches to identify ligand-receptor interactions have gained popularity. However, identifying transmembrane receptors remains challenging. A new trifunctional probe to aid the nonbiased identification of such receptors was developed and synthesized using a convenient seven-step synthesis. This probe contained three functional groups: 1) an N-hydroxysuccinimide ester for ligand-coupling through free amines, 2) a diazirine moiety to capture the receptor of interest upon irradiation with UV light, and 3) a biotin group which allowed affinity purification of the final adduct using streptavidin. The interaction between the G protein-coupled tachykinin neurokinin 1 (NK1) receptor, expressed in an inducible manner, and the peptidic ligand substance P was used as a test system. Liquid chromatography-mass spectrometry analysis confirmed successful coupling of the probe to substance P, while inositol monophosphate accumulation assays demonstrated that coupling of the probe did not interfere substantially with the substance P-NK1 receptor interaction. Confocal microscopy and western blotting provided evidence of the formation of a covalent bond between the probe and the NK1 receptor upon UV activation. As proof of concept, the probe was used in full ligand-based receptor-capture experiments to identify the substance P-binding receptor via liquid chromatography-tandem mass spectrometry, resulting in the successful identification of only the NK1 receptor. This provides proof of concept toward general utilization of this probe to define interactions between ligands and previously unidentified plasma-membrane receptors
Versatile Click Linker Enabling Native Peptide Release from Nanocarriers upon Redox Trigger
Nanocarriers have
shown their ability to extend the circulation
time of drugs, enhance tumor uptake, and tune drug release. Therapeutic
peptides are a class of drug compounds in which nanocarrier-mediated
delivery can potentially improve their therapeutic index. To this
end, there is an urgent need for orthogonal covalent linker chemistry
facilitating the straightforward on-the-resin peptide generation,
nanocarrier conjugation, as well as the triggered release of the peptide
in its native state. Here, we present a copper-free clickable ring-strained
alkyne linker conjugated to the N-terminus of oncolytic peptide LTX-315
via standard solid-phase peptide synthesis (SPPS). The linker contains
(1) a recently developed seven-membered ring-strained alkyne, 3,3,6,6-tetramethylthiacycloheptyne
sulfoximine (TMTHSI), (2) a disulfide bond, which is sensitive to
the reducing cytosolic and tumor environment, and (3) a thiobenzyl
carbamate spacer enabling release of the native peptide upon cleavage
of the disulfide via 1,6-elimination. We demonstrate convenient “clicking”
of the hydrophilic linker–peptide conjugate to preformed pegylated
core-cross-linked polymeric micelles (CCPMs) of 50 nm containing azides
in the hydrophobic core under aqueous conditions at room temperature
resulting in a loading capacity of 8 mass % of peptide to polymer
(56% loading efficiency). This entrapment of hydrophilic cargo into/to
a cross-linked hydrophobic core is a new and counterintuitive approach
for this class of nanocarriers. The release of LTX-315 from the CCPMs
was investigated in vitro and rapid release upon exposure to glutathione
(within minutes) followed by slower 1,6-elimination (within an hour)
resulted in the formation of the native peptide. Finally, cytotoxicity
of LTX CCPMs as well as uptake of sulfocyanine 5-loaded CCPMs was
investigated by cell culture, demonstrating successful tumor cell
killing at concentrations similar to that of the free peptide treatment