TY - JOUR

T1 - Mapping Substance P Binding Sites on the Neurokinin-1 Receptor Using Genetic Incorporation of a Photoreactive Amino Acid

AU - Valentin-Hansen, Louise

AU - Park, Minyoung

AU - Huber, Thomas

AU - Grunbeck, Amy

AU - Naganathan, Saranga

AU - Schwartz, Thue W.

AU - Sakmar, Thomas P

N1 - © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

PY - 2014/6/27

Y1 - 2014/6/27

N2 - Substance P (SP) is a neuropeptide that mediates numerous physiological responses, including transmission of pain and inflammation through the neurokinin-1 (NK1) receptor, a G protein-coupled receptor. Previous mutagenesis studies and photoaffinity labeling using ligand analogues suggested that the binding site for SP includes multiple domains in the N-terminal (Nt) segment and the second extracellular loop (ECLII) of NK1. To map precisely the NK1 residues that interact with SP, we applied a novel receptor-based targeted photocross-linking approach. We used amber codon suppression to introduce the photoreactive unnatural amino acid p-benzoyl-l-phenylalanine (BzF) at 11 selected individual positions in the Nt tail (residues 11-21) and 23 positions in the ECLII (residues 170(C-10)-193(C+13)) of NK1. The 34 NK1 variants were expressed in mammalian HEK293 cells and retained the ability to interact with a fluorescently labeled SP analog. Notably, 10 of the receptor variants with BzF in the Nt tail and 4 of those with BzF in ECLII cross-linked efficiently to SP, indicating that these 14 sites are juxtaposed to SP in the ligand-bound receptor. These results show that two distinct regions of the NK1 receptor possess multiple determinants for SP binding and demonstrate the utility of genetically encoded photocross-linking to map complex multitopic binding sites on G protein-coupled receptors in a cell-based assay format.

AB - Substance P (SP) is a neuropeptide that mediates numerous physiological responses, including transmission of pain and inflammation through the neurokinin-1 (NK1) receptor, a G protein-coupled receptor. Previous mutagenesis studies and photoaffinity labeling using ligand analogues suggested that the binding site for SP includes multiple domains in the N-terminal (Nt) segment and the second extracellular loop (ECLII) of NK1. To map precisely the NK1 residues that interact with SP, we applied a novel receptor-based targeted photocross-linking approach. We used amber codon suppression to introduce the photoreactive unnatural amino acid p-benzoyl-l-phenylalanine (BzF) at 11 selected individual positions in the Nt tail (residues 11-21) and 23 positions in the ECLII (residues 170(C-10)-193(C+13)) of NK1. The 34 NK1 variants were expressed in mammalian HEK293 cells and retained the ability to interact with a fluorescently labeled SP analog. Notably, 10 of the receptor variants with BzF in the Nt tail and 4 of those with BzF in ECLII cross-linked efficiently to SP, indicating that these 14 sites are juxtaposed to SP in the ligand-bound receptor. These results show that two distinct regions of the NK1 receptor possess multiple determinants for SP binding and demonstrate the utility of genetically encoded photocross-linking to map complex multitopic binding sites on G protein-coupled receptors in a cell-based assay format.

KW - Amino Acid Motifs

KW - Amino Acid Sequence

KW - Binding Sites

KW - Crystallography, X-Ray

KW - Humans

KW - Models, Molecular

KW - Photoaffinity Labels

KW - Protein Binding

KW - Protein Structure, Tertiary

KW - Receptors, Neurokinin-1

KW - Substance P

KW - Ultraviolet Rays

U2 - 10.1074/jbc.M113.527085

DO - 10.1074/jbc.M113.527085

M3 - Journal article

C2 - 24831006

VL - 289

SP - 18045

EP - 18054

JO - Journal of Biological Chemistry

JF - Journal of Biological Chemistry

SN - 0021-9258

IS - 26

ER -