I am a
Home I AM A Search Login

Papers of the Week

Papers: 20 May 2023 - 26 May 2023

Basic Science

Animal Studies, Molecular/Cellular, Neurobiology, Pharmacology/Drug Development

2023 May 30

Proc Natl Acad Sci U S A




Therapeutic antagonism of the neurokinin 1 receptor in endosomes provides sustained pain relief.


Hegron A, Peach CJ, Tonello R, Seemann P, Teng S, Latorre R, Huebner H, Weikert D, Rientjes J, Veldhuis NA, Poole DP, Jensen DD, Thomsen ARB, Schmidt BL, Imlach WL, Gmeiner P, Bunnett NW


The hypothesis that sustained G protein-coupled receptor (GPCR) signaling from endosomes mediates pain is based on studies with endocytosis inhibitors and lipid-conjugated or nanoparticle-encapsulated antagonists targeted to endosomes. GPCR antagonists that reverse sustained endosomal signaling and nociception are needed. However, the criteria for rational design of such compounds are ill-defined. Moreover, the role of natural GPCR variants, which exhibit aberrant signaling and endosomal trafficking, in maintaining pain is unknown. Herein, substance P (SP) was found to evoke clathrin-mediated assembly of endosomal signaling complexes comprising neurokinin 1 receptor (NKR), Gα, and βarrestin-2. Whereas the FDA-approved NKR antagonist aprepitant induced a transient disruption of endosomal signals, analogs of netupitant designed to penetrate membranes and persist in acidic endosomes through altered lipophilicity and pKa caused sustained inhibition of endosomal signals. When injected intrathecally to target spinal NKR+ve neurons in knockin mice expressing human NKR, aprepitant transiently inhibited nociceptive responses to intraplantar injection of capsaicin. Conversely, netupitant analogs had more potent, efficacious, and sustained antinociceptive effects. Mice expressing C-terminally truncated human NKR, corresponding to a natural variant with aberrant signaling and trafficking, displayed attenuated SP-evoked excitation of spinal neurons and blunted nociceptive responses to SP. Thus, sustained antagonism of the NKR in endosomes correlates with long-lasting antinociception, and domains within the C-terminus of the NKR are necessary for the full pronociceptive actions of SP. The results support the hypothesis that endosomal signaling of GPCRs mediates nociception and provides insight into strategies for antagonizing GPCRs in intracellular locations for the treatment of diverse diseases.