Human Substance P Interactions with G Protein-Coupled Receptor NK1R Observed by NMR in Solution

Area of Science:

• Biochemistry
• Structural Biology
• Neuroscience

Background:

• Neurokinin 1 receptor (NK1R) is a G protein-coupled receptor involved in nausea, inflammation, and neurological disorders.
• Previous cryogenic electron microscopy (cryo-EM) studies of NK1R-Substance P (SP) complexes did not resolve the N-terminal peptide segments.

Purpose of the Study:

• To explore the impact of N-terminal peptide segments of NK1R and SP on their structure and function.
• To characterize the dynamic interactions between NK1R and SP.

Main Methods:

• Utilized fluorine-19 NMR spectroscopy with a 3-trifluoromethyl-l-phenylalanine (mtfF) probe incorporated into Substance P (SP).
• Observed SP in solution, in micelles, and bound to micelle-solubilized NK1R.
• Performed cyclic adenosine monophosphate (cAMP) function assays.

Main Results:

• NMR data indicated that the N-terminal pentapeptide of SP is flexible and solvent-exposed when bound to NK1R.
• The C-terminal hexapeptide of SP is rigidly anchored within the NK1R orthosteric pocket.
• Transient interactions involving Lys3 and Gln5 of SP influenced NK1R functional properties.

Conclusions:

• Specific dynamic intermolecular interactions between the N-terminal segments of SP and NK1R were identified.
• These interactions significantly impact the functional potency of SP.
• Understanding these dynamics is crucial for NK1R-targeted therapeutics.