scholarly journals Cryo-EM structure of human somatostatin receptor 2 complex with its agonist somatostatin delineates the ligand binding specificity

2022 ◽  
Author(s):  
Yunseok Heo ◽  
Eojin Yoon ◽  
Ye-Eun Jeon ◽  
Ji-Hye Yun ◽  
Naito Ishimoto ◽  
...  
Keyword(s):  
Sequence Analysis ◽  
High Resolution ◽  
Ligand Binding ◽  
Neurological Disorders ◽  
Somatostatin Receptor ◽  
Somatostatin Receptors ◽  
Peptide Hormone ◽  
Transmembrane Helices ◽  
G Protein Coupled ◽  
Gi Proteins

Somatostatin is a peptide hormone regulating endocrine systems through binding to G-protein-coupled somatostatin receptors. somatostatin receptor 2 (SSTR2) is one of the human somatostatin receptors and highly implicated in cancers and neurological disorders. Here, we report the high resolution cryo-EM structure of full-length human SSTR2 bound to the agonist somatostatin (SST-14) complex with inhibitory G (Gi) proteins. Our structure shows that seven transmembrane helices form a deep pocket for ligand binding and that the highly conserved Trp-Lys motif of SST-14 positions at the bottom of the pocket. Furthermore, our sequence analysis combined with AlphaFold modeled structures of other SSTR isoforms provide how SSTR family proteins specifically interact with their cognate ligands. This work provides the first glimpse into the molecular recognition of somatostatin receptor and crucial resource to develop therapeutics targeting somatostatin receptors.

scholarly journals Pharmacological Characterization of Veldoreotide as a Somatostatin Receptor 4 Agonist

Life ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1075
Author(s):  
Pooja Dasgupta ◽  
Thomas Gűnther ◽  
Stefan Schulz
Keyword(s):  
Cell Proliferation ◽  
G Protein ◽  
Somatostatin Receptor ◽  
Somatostatin Receptors ◽  
Hek293 Cells ◽  
Somatostatin Analogue ◽  
Protein Signaling ◽  
Pharmacological Characterization ◽  
The Individual ◽  
G Protein Coupled

Veldoreotide, a somatostatin analogue, binds to the somatostatin receptors (SSTR) 2, 4, and 5. The current aim was to assess its pharmacological activity as an SSTR4 agonist. G-protein signaling was assessed using a fluorescence-based membrane potential assay in human embryonic kidney 293 (HEK293) cells stably co-expressing G-protein‒coupled inwardly rectifying potassium 2 channels and the individual SSTR2, SSTR4, and SSTR5, and in human BON-1 cells stably expressing these SSTRs. Veldoreotide effects on chromogranin A (CgA) secretion and cell proliferation were examined in BON-1 cells. In HEK293 transfected cells, veldoreotide showed a high efficacy for activating the SSTR4; octreotide and pasireotide had little activity (Emax, 99.5% vs. 27.4% and 52.0%, respectively). Veldoreotide also activated SSTR2 and SSTR5 (Emax, 98.4% and 96.9%, respectively). In BON-1 cells, veldoreotide activated SSTR2, SSTR4, and SSTR5 with high potency and efficacy. CgA secretion was decreased to a greater degree in the BON-1 cells expressing SSTR4 versus the cells expressing SSTR2 and SSTR5 (65.3% vs. 80.3% and 77.6%, respectively). In the BON-1 cells expressing SSTR4, veldoreotide inhibited cell proliferation more than somatostatin SS-14 (71.2% vs. 79.7%) and to a similar extent as the SSTR4 agonist J-2156 in the presence of SSTR2 and SSTR5 antagonists. Veldoreotide is a full agonist of SSTR2, SSTR4, and SSTR5.

scholarly journals Immunohistochemical Expression of Somatostatin Receptor Subtypes in a Panel of Neuroendocrine Neoplasias

2019 ◽  
Vol 67 (10) ◽  
pp. 735-743 ◽  
Author(s):  
Satu M. Remes ◽  
Helena L. Leijon ◽  
Tiina J. Vesterinen ◽  
Johanna T. Arola ◽  
Caj H. Haglund
Keyword(s):  
Somatostatin Receptor ◽  
Somatostatin Receptors ◽  
Somatostatin Analogs ◽  
Membrane Receptors ◽  
Receptor Subtypes ◽  
Receptor Imaging ◽  
Primary Tumors ◽  
Somatostatin Receptor Subtypes ◽  
Negative Controls ◽  
G Protein Coupled

Neuroendocrine neoplasias (NENs) are known to express somatostatin receptors (SSTRs) 1–5, which are G-protein-coupled cell membrane receptors. Somatostatin receptor imaging and therapy utilizes the SSTR expression. Synthetic somatostatin analogs with radioligands are used to detect primary tumors, metastases, and recurrent disease. Receptor analogs are also used for treating NENs. Furthermore, commercially available SSTR antibodies can be used for the immunohistochemical (IHC) detection of SSTRs. We investigated different SSTR antibody clones applying diverse IHC protocol settings to identify reliable clones and feasible protocols for NENs. A tissue microarray including NENs from 12 different primary sites were stained. Only UMB clones were able to localize SSTR on the cell membranes of NENs. SSTR2 (UMB1) emerged as the most common subtype followed by SSTR5 (UMB4) and SSTR1 (UMB7). SSTR3 (UMB5) expression was mainly cytoplasmic. Yet, SSTR4 expression was weak and located primarily in the cytoplasm. Thus, appropriate IHC protocols, including proper positive and negative controls, represent requirements for high-quality NEN diagnostics and for planning personalized therapy.

Extracellular loops and ligand binding to a subfamily of Family A G-protein-coupled receptors

2007 ◽  
Vol 35 (4) ◽  
pp. 717-720 ◽  
Author(s):  
M. Wheatley ◽  
J. Simms ◽  
S.R. Hawtin ◽  
V.J. Wesley ◽  
D. Wootten ◽  
...  
Keyword(s):  
Ligand Binding ◽  
G Protein ◽  
Tertiary Structure ◽  
Large Family ◽  
Peptide Hormone ◽  
Receptor Activation ◽  
G Protein Coupled Receptors ◽  
Ligand Selectivity ◽  
Extracellular Loops ◽  
G Protein Coupled

GPCRs (G-protein-coupled receptors) are a large family of structurally related proteins which mediate their effects by coupling to G-proteins. The V1aR (V1a vasopressin receptor) is a member of a family of related GPCRs that are activated by vasopressin {AVP ([Arg8]vasopressin)}, OT (oxytocin) and related peptides. These receptors are members of a subfamily of Family A GPCRs called the neurohypophysial peptide hormone receptor family. GPCRs exhibit a conserved tertiary structure comprising a bundle of seven TM (transmembrane) helices linked by alternating ECLs (extracellular loops) and ICLs (intracellular loops). The cluster of TM helices is functionally important for ligand binding, and, furthermore, activation of GPCRs involves movement of these TM helices. Consequently, it might be assumed that the extracellular face of GPCRs is composed of peptide linkers that merely connect important TM helices. However, using a systematic mutagenesis approach and focusing on the N-terminus and the second ECL of the V1aR, we have established that these extracellular domains fulfil a range of important roles with respect to GPCR signalling, including agonist binding, ligand selectivity and receptor activation.

scholarly journals Mutagenesis facilitated crystallization of GLP-1R

IUCrJ ◽  
2019 ◽  
Vol 6 (6) ◽  
pp. 996-1006 ◽  
Author(s):  
Yueming Xu ◽  
Yuxia Wang ◽  
Yang Wang ◽  
Kaiwen Liu ◽  
Yao Peng ◽  
...  
Keyword(s):  
Hydrophobic Interactions ◽  
Crystal Packing ◽  
Peptide Hormone ◽  
Current Data ◽  
Transmembrane Helices ◽  
Dynamic Simulations ◽  
Class B ◽  
Glucagon Like Peptide 1 ◽  
Diabetes Drug ◽  
G Protein Coupled

The class B family of G-protein-coupled receptors (GPCRs) has long been a paradigm for peptide hormone recognition and signal transduction. One class B GPCR, the glucagon-like peptide-1 receptor (GLP-1R), has been considered as an anti-diabetes drug target and there are several peptidic drugs available for the treatment of this overwhelming disease. The previously determined structures of inactive GLP-1R in complex with two negative allosteric modulators include ten thermal-stabilizing mutations that were selected from a total of 98 designed mutations. Here we systematically summarize all 98 mutations we have tested and the results suggest that the mutagenesis strategy that strengthens inter-helical hydrophobic interactions shows the highest success rate. We further investigate four back mutations by thermal-shift assay, crystallization and molecular dynamic simulations, and conclude that mutation I1962.66bF increases thermal stability intrinsically and that mutation S2714.47bA decreases crystal packing entropy extrinsically, while mutations S1932.63bC and M2333.36bC may be dispensable since these two cysteines are not disulfide-linked. Our results indicate intrinsic connections between different regions of GPCR transmembrane helices and the current data suggest a general mutagenesis principle for structural determination of GPCRs and other membrane proteins.

scholarly journals Role of Somatostatin Receptor in Pancreatic Neuroendocrine Tumor Development, Diagnosis, and Therapy

2021 ◽  
Vol 12 ◽  
Author(s):  
Yuheng Hu ◽  
Zeng Ye ◽  
Fei Wang ◽  
Yi Qin ◽  
Xiaowu Xu ◽  
...  
Keyword(s):  
Clinical Significance ◽  
Somatostatin Receptor ◽  
Relevant Literature ◽  
Somatostatin Receptors ◽  
Tumor Development ◽  
Pancreatic Neuroendocrine Tumor ◽  
Neuroendocrine Neoplasms ◽  
Prognostic Prediction ◽  
G Protein Coupled

Pancreatic neuroendocrine tumors (pNETs) are rare and part of the diverse family of neuroendocrine neoplasms (NENs). Somatostatin receptors (SSTRs), which are widely expressed in NENs, are G-protein coupled receptors that can be activated by somatostatins or its synthetic analogs. Therefore, SSTRs have been widely researched as a diagnostic marker and therapeutic target in pNETs. A large number of studies have demonstrated the clinical significance of SSTRs in pNETs. In this review, relevant literature has been appraised to summarize the most recent empirical evidence addressing the clinical significance of SSTRs in pNETs. Overall, these studies have shown that SSTRs have great value in the diagnosis, treatment, and prognostic prediction of pNETs; however, further research is still necessary.

scholarly journals Changes in Conformation at the Cytoplasmic Ends of the Fifth and Sixth Transmembrane Helices of a Yeast G Protein-Coupled Receptor in Response to Ligand Binding

Biochemistry ◽  
2011 ◽  
Vol 50 (32) ◽  
pp. 6841-6854 ◽  
Author(s):  
George K. E. Umanah ◽  
Li-Yin Huang ◽  
Julianna M. Maccarone ◽  
Fred Naider ◽  
Jeffrey M. Becker
Keyword(s):  
Ligand Binding ◽  
G Protein ◽  
Transmembrane Helices ◽  
G Protein Coupled Receptor ◽  
G Protein Coupled

scholarly journals Phosphorylation of Threonine 333 Regulates Trafficking of the Human sst5 Somatostatin Receptor

2013 ◽  
Vol 27 (4) ◽  
pp. 671-682 ◽  
Author(s):  
Aline Petrich ◽  
Anika Mann ◽  
Andrea Kliewer ◽  
Falko Nagel ◽  
Anne Strigli ◽  
...  
Keyword(s):  
G Protein ◽  
Protein Phosphatase ◽  
Somatostatin Receptor ◽  
Somatostatin Receptors ◽  
Somatostatin Analogs ◽  
Receptor Kinase ◽  
G Protein Coupled Receptor ◽  
Selective Ligand ◽  
Carboxyl Terminal ◽  
G Protein Coupled

Abstract The frequent overexpression of the somatostatin receptors sst2 and sst5 in neuroendocrine tumors provides the molecular basis for therapeutic application of novel multireceptor somatostatin analogs. Although the phosphorylation of the carboxyl-terminal region of the sst2 receptor has been studied in detail, little is known about the agonist-induced regulation of the human sst5 receptor. Here, we have generated phosphosite-specific antibodies for the carboxyl-terminal threonines 333 (T333) and 347 (T347), which enabled us to selectively detect either the T333-phosphorylated or the T347-phosphorylated form of sst5. We show that agonist-mediated phosphorylation occurs at T333, whereas T347 is constitutively phosphorylated in the absence of agonist. We further demonstrate that the multireceptor somatostatin analog pasireotide and the sst5-selective ligand L-817,818 but not octreotide or KE108 were able to promote a detectable T333 phosphorylation. Interestingly, BIM-23268 was the only sst5 agonist that was able to stimulate T333 phosphorylation to the same extent as natural somatostatin. Agonist-induced T333 phosphorylation was dose-dependent and selectively mediated by G protein-coupled receptor kinase 2. Similar to that observed for the sst2 receptor, phosphorylation of sst5 occurred within seconds. However, unlike that seen for the sst2 receptor, dephosphorylation and recycling of sst5 were rapidly completed within minutes. We also identify protein phosphatase 1γ as G protein-coupled receptor phosphatase for the sst5 receptor. Together, we provide direct evidence for agonist-selective phosphorylation of carboxyl-terminal T333. In addition, we identify G protein-coupled receptor kinase 2-mediated phosphorylation and protein phosphatase 1γ-mediated dephosphorylation of T333 as key regulators of rapid internalization and recycling of the human sst5 receptor.

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