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Neurotensin (NTS) is a 13-amino-acid peptide that functions as both a neurotransmitter and a hormone through the activation of the neurotensin receptor NTSR1, a G-protein-coupled receptor (GPCR). In the brain, NTS modulates the activity of dopaminergic systems, opioid-independent analgesia, and the inhibition of food intake; in the gut, NTS regulates a range of digestive processes. Here we present the structure at 2.8 Å resolution of Rattus norvegicus NTSR1 in an active-like state, bound to NTS 8–13 , the carboxy-terminal portion of NTS responsible for agonist-induced activation of the receptor. The peptide agonist binds to NTSR1 in an extended conformation nearly perpendicular to the membrane plane, with the C terminus oriented towards the receptor core. Our findings provide, to our knowledge, the first insight into the binding mode of a peptide agonist to a GPCR and may support the development of non-peptide ligands that could be useful in the treatment of neurological disorders, cancer and obesity. The X-ray crystal structure of a rat neurotensin receptor in complex with the C-terminal portion of neurotensin is presented; this is the first structure of a member of the β group of class A G-protein-coupled receptors. GPCR–peptide agonist structure determined Neurotensin is a short peptide that can act as a neurotransmitter, a digestive hormone, and a regulator of cardiac output and blood pressure. In this manuscript, the authors solve an X-ray crystal structure of the carboxy-terminal portion of neurotensin bound to a rat neurotensin receptor. This is the first structure of a member of the beta group of class A G-protein-coupled receptors (GPCRs), and the first published structure of a GPCR bound to a peptide agonist. This structure should facilitate the development of non-peptide drugs that could be used to treat neurological disorders, cancer and obesity.

G-protein-coupled receptors (GPCRs) are the largest superfamily of transmembrane proteins and the targets of over 30% of currently marketed pharmaceuticals. Although several structures have been solved for GPCR–G protein complexes, few are in a lipid membrane environment. Here, we report cryo-EM structures of complexes of neurotensin, neurotensin receptor 1 and Gα i1 β 1 γ 1 in two conformational states, resolved to resolutions of 4.1 and 4.2 Å. The structures, determined in a lipid bilayer without any stabilizing antibodies or nanobodies, reveal an extended network of protein–protein interactions at the GPCR–G protein interface as compared to structures obtained in detergent micelles. The findings show that the lipid membrane modulates the structure and dynamics of complex formation and provide a molecular explanation for the stronger interaction between GPCRs and G proteins in lipid bilayers. We propose an allosteric mechanism for GDP release, providing new insights into the activation of G proteins for downstream signaling. Structures of GPCR neurotensin receptor 1 (NTSR1) in complex with neurotensin and Gα i1 β 1 γ 1 in a lipid bilayer environment and without stabilizing antibodies reveal extensive interactions at the GPCR–G protein interface.

G protein-coupled receptors (GPCRs) are the largest class of membrane receptors, playing a key role in the regulation of processes as varied as neurotransmission and immune response. Evidence for GPCR oligomerisation has been accumulating that challenges the idea that GPCRs function solely as monomeric receptors; however, GPCR oligomerisation remains controversial primarily due to the difficulties in comparing evidence from very different types of structural and dynamic data. Using a combination of single-molecule and ensemble FRET, double electron–electron resonance spectroscopy, and simulations, we show that dimerisation of the GPCR neurotensin receptor 1 is regulated by receptor density and is dynamically tuneable over the physiological range. We propose a “rolling dimer” interface model in which multiple dimer conformations co-exist and interconvert. These findings unite previous seemingly conflicting observations, provide a compelling mechanism for regulating receptor signalling, and act as a guide for future physiological studies. Evidence suggests oligomerisation of G protein-coupled receptors in membranes, but this is controversial. Here, authors use single-molecule and ensemble FRET, and spectroscopy to show that the neurotensin receptor 1 forms multiple dimer conformations that interconvert - “rolling” interfaces.

Neurotensin, a peptide expressed in the enteroendocrine cells of the small intestine that is released upon fat ingestion, is shown to increase fatty acid absorption, with neurotensin-deficient mice being protected from obesity induced by a high-fat diet. Neurotensin is a factor in obesity Neurotensin (NT) is a 13-amino-acid peptide expressed in the enteroendocrine cells of the small bowel, and is released upon fat ingestion to facilitate fatty acid translocation. There are three known NT receptors, termed NTR1, NTR2 and NTR3. These authors show that NT increases fatty acid absorption and inhibition of downstream AMPK activity in intestinal cells via NTR1 and NTR3. Mice deficient in NT and on a high fat diet are protected from obesity, hepatic steatosis and insulin resistance, unlike their wild-type counterparts. Expression of NT in enteroendocrine cells of the fly increases lipid accumulation in the midgut, fat body and oenocytes, and also decreases AMPK activity, suggesting conservation of the pathway. Obese and insulin-resistant humans are shown to have elevated plasma levels of pro-NT, a precursor of NT, and high levels of pro-NT double the risk of obesity later in life. Obesity and its associated comorbidities (for example, diabetes mellitus and hepatic steatosis) contribute to approximately 2.5 million deaths annually 1 and are among the most prevalent and challenging conditions confronting the medical profession 2 , 3 . Neurotensin (NT; also known as NTS), a 13-amino-acid peptide predominantly localized in specialized enteroendocrine cells of the small intestine 4 and released by fat ingestion 5 , facilitates fatty acid translocation in rat intestine 6 , and stimulates the growth of various cancers 7 . The effects of NT are mediated through three known NT receptors (NTR1, 2 and 3; also known as NTSR1, 2, and NTSR3, respectively) 8 . Increased fasting plasma levels of pro-NT (a stable NT precursor fragment produced in equimolar amounts relative to NT) are associated with increased risk of diabetes, cardiovascular disease and mortality 9 ; however, a role for NT as a causative factor in these diseases is unknown. Here we show that NT-deficient mice demonstrate significantly reduced intestinal fat absorption and are protected from obesity, hepatic steatosis and insulin resistance associated with high fat consumption. We further demonstrate that NT attenuates the activation of AMP-activated protein kinase (AMPK) and stimulates fatty acid absorption in mice and in cultured intestinal cells, and that this occurs through a mechanism involving NTR1 and NTR3 (also known as sortilin). Consistent with the findings in mice, expression of NT in Drosophila midgut enteroendocrine cells results in increased lipid accumulation in the midgut, fat body, and oenocytes (specialized hepatocyte-like cells) and decreased AMPK activation. Remarkably, in humans, we show that both obese and insulin-resistant subjects have elevated plasma concentrations of pro-NT, and in longitudinal studies among non-obese subjects, high levels of pro-NT denote a doubling of the risk of developing obesity later in life. Our findings directly link NT with increased fat absorption and obesity and suggest that NT may provide a prognostic marker of future obesity and a potential target for prevention and treatment.

IntroductionDespite recent developments in the diagnosis and treatment of prostate cancer, the advanced stages still have poor survival rates. This warrants further exploration of related molecular targets for patient screening, detection of metastatic disease, and treatment/treatment monitoring. Recent studies have indicated that neurotensin receptors (NTSRs) and their ligand neurotensin (NTS) critically affect the progression of prostate cancers. In this study, we evaluated the expression of neurotensin receptor1 (NTSR1) in patient tissues and performed NTSR1 PET imaging in a prostate cancer animal model.MethodsThe NTSR1 expression was evaluated in 97 cases of prostate cancer and 100 cases of benign prostatic hyperplasia (BPH) of clinical patients by immunohistochemistry staining. The expression profile of PSMA and GRPR was also performed for comparison. The mRNA expression of NTSR1 in LnCap and PC-3 cells was measured by PCR. NTSR1 PET, and biodistribution studies were performed in PC-3 xenografts using 18F-DEG-VS-NT.ResultsNTSR1 showed high or moderate expression in 91.8% of prostate cancer tissue, compared with PSMA (86.7%) and GRPR (65.3%). All examined PSMA-negative tissues showed positive NTSR1 expression, suggesting the potential complementary role of NTSR1 targeted imaging or therapy. Only 8% of BPH shows strong or moderate expression of NTSR1, which is significantly lower than that in prostate cancer (91.8%). PCR results indicated LNCap (an androgen-dependent prostate cancer cell) showed negative NTSR1 expression while PC-3 demonstrated positive expression (an androgen-independent prostate cancer cell), which correlated well with previously reported western blot results. In a preclinical animal model, NTSR1 targeted PET probe 18F-DEG-VS-NT demonstrated prominent tumor accumulation and low background.ConclusionWe have demonstrated that NTSR1 is a promising molecular marker for prostate cancer based on patient tissue staining. The NTSR targeted probe 18F-DEG-VS-NT demonstrated high tumor to background contrast in animal models, which could be valuable in selecting patients for therapies targeting NTSR1 as well as monitoring therapeutic efficacy during treatment accordingly.

Arrestin proteins bind to active, phosphorylated G-protein-coupled receptors (GPCRs), thereby preventing G-protein coupling, triggering receptor internalization and affecting various downstream signalling pathways 1 , 2 . Although there is a wealth of structural information detailing the interactions between GPCRs and G proteins, less is known about how arrestins engage GPCRs. Here we report a cryo-electron microscopy structure of full-length human neurotensin receptor 1 (NTSR1) in complex with truncated human β-arrestin 1 (βarr1(ΔCT)). We find that phosphorylation of NTSR1 is critical for the formation of a stable complex with βarr1(ΔCT), and identify phosphorylated sites in both the third intracellular loop and the C terminus that may promote this interaction. In addition, we observe a phosphatidylinositol-4,5-bisphosphate molecule forming a bridge between the membrane side of NTSR1 transmembrane segments 1 and 4 and the C-lobe of arrestin. Compared with a structure of a rhodopsin–arrestin-1 complex, in our structure arrestin is rotated by approximately 85° relative to the receptor. These findings highlight both conserved aspects and plasticity among arrestin–receptor interactions. A cryo-electron microscopy structure of the neurotensin receptor 1 in complex with β-arrestin 1 is reported.

G protein-coupled receptors (GPCRs) are critical to a variety of pathophysiological processes, making them attractive targets for the development of drugs or relevant diagnostic tools. Although GPCRs have been successfully targeted with small molecules, the production of reliable anti-GPCR antibodies remains a major challenge. To address this issue, we develop a strategy using macrocyclic peptides designed to mimic the three-dimensional structure of GPCR extracellular loops as immunogens and use the chicken, which is genetically distant from mammals, as an immunization host to produce antigen-specific antibodies. The high-affinity neurotensin receptor type 1 (NTS1), overexpressed in many types of human cancer and associated with poor prognosis, is used as a target. Rational design of macrocyclic epitope mimics and linker selection are achieved using modeling and predictive analysis software tools based on available NTS1 crystal structures. This study particularly highlights the critical role of the linker in peptide macrocyclization, which determines whether antibodies can exert antagonistic activity. Overall, this strategy represents a valuable asset to produce effective spatial anti-GPCR antibodies and holds promise for diagnostic and therapeutic applications. In this work, functional antibodies against the cancer-related GPCR NTS1 were generated by immunizing chickens with in silico-designed 3D peptides, offering a strategy for GPCR targeting with potential diagnostic and therapeutic applications.

Neurotensin (NTS) is a secretory peptide produced by lymphatic endothelial cells. Our previous study revealed that NTS suppressed the activity of brown adipose tissue via interactions with NTSR2. In the current study, we found that the depletion of Ntsr2 in white adipocytes upregulated food intake, while the local treatment of NTS suppressed food intake. Our mechanistic study revealed that suppression of NTS-NTSR2 signaling enhanced the phosphorylation of ceramide synthetase 2, increased the abundance of its products ceramides C20–C24, and downregulated the production of GDF15 in white adipose tissues, which was responsible for the elevation of food intake. We discovered a potential causal and positive correlation between serum C20–C24 ceramide levels and human food intake in four populations with different ages and ethnic backgrounds. Together, our study shows that NTS-NTSR2 signaling in white adipocytes can regulate food intake via its direct control of lipid metabolism and production of GDF15. The ceramides C20–C24 are key factors regulating food intake in mammals.

Sepsis is a complex, incompletely understood and often fatal disorder, typically accompanied by hypotension, that is considered to represent a dysregulated host response to infection. Neurotensin (NT) is a 13-amino-acid peptide that, among its multiple effects, induces hypotension. We find that intraperitoneal and plasma concentrations of NT are increased in mice after severe cecal ligation and puncture (CLP), a model of sepsis, and that mice treated with a pharmacological antagonist of NT, or NT-deficient mice, show reduced mortality during severe CLP. In mice, mast cells can degrade NT and reduce NT-induced hypotension and CLP-associated mortality, and optimal expression of these effects requires mast cell expression of neurotensin receptor 1 and neurolysin. These findings show that NT contributes to sepsis-related mortality in mice during severe CLP and that mast cells can lower NT concentrations, and suggest that mast cell–dependent reduction in NT levels contributes to the ability of mast cells to enhance survival after CLP.