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 Critical Role of Src and SHP-2 in sst2 Somatostatin Receptor-mediated Activation of SHP-1 and Inhibition of Cell Proliferation

2003 ◽  
Vol 14 (9) ◽  
pp. 3911-3928 ◽  
Author(s):  
Geraldine Ferjoux ◽  
Frederic Lopez ◽  
Jean-Pierre Esteve ◽  
Audrey Ferrand ◽  
Eric Vivier ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Cell Growth ◽  
G Protein ◽  
Tyrosine Phosphatase ◽  
Somatostatin Receptor ◽  
Critical Role ◽  
Inhibitory G Protein ◽  
G Protein Coupled ◽  
Mutation Analyses

The G protein-coupled sst2 somatostatin receptor acts as a negative cell growth regulator. Sst2 transmits antimitogenic signaling by recruiting and activating the tyrosine phosphatase SHP-1. We now identified Src and SHP-2 as sst2-associated molecules and demonstrated their role in sst2 signaling. Surface plasmon resonance and mutation analyses revealed that SHP-2 directly associated with phosphorylated tyrosine 228 and 312, which are located in sst2 ITIMs (immunoreceptor tyrosine-based inhibitory motifs). This interaction was required for somatostatin-induced SHP-1 recruitment and activation and consequent inhibition of cell proliferation. Src interacted with sst2 and somatostatin promoted a transient Gβγ-dependent Src activation concomitant with sst2 tyrosine hyperphosphorylation and SHP-2 activation. These steps were abrogated with catalytically inactive Src. Both catalytically inactive Src and SHP-2 mutants abolished somatostatin-induced SHP-1 activation and cell growth inhibition. Sst2–Src–SHP-2 complex formation was dynamic. Somatostatin further induced sst2 tyrosine dephosphorylation and complex dissociation accompanied by Src and SHP-2 inhibition. These steps were defective in cells expressing a catalytically inactive Src mutant. All these data suggest that Src acts upstream of SHP-2 in sst2 signaling and provide evidence for a functional role for Src and SHP-2 downstream of an inhibitory G protein-coupled receptor.

scholarly journals SAT-305 Veldoreotide (COR005) Mechanisms of Action Studies: Comparison to Octreotide and Pasireotide

2020 ◽  
Vol 4 (Supplement_1) ◽  
Author(s):  
Pooja Dasgupta ◽  
Stefan Schulz
Keyword(s):  
G Protein ◽  
Somatostatin Receptor ◽  
Somatostatin Analogs ◽  
Hek293 Cells ◽  
Receptor Subtypes ◽  
G Protein Signaling ◽  
Protein Signaling ◽  
Response Curves ◽  
Somatostatin Receptor Subtypes ◽  
First Choice

Abstract Stable somatostatin analogs (SSAs) are the first choice for medical treatment of pituitary adenomas and other neuroendocrine tumors. The somatostatin analogs octreotide, pasireotide, and veldoreotide primarily have been characterized according to their binding profiles. However, their ability to activate individual somatostatin receptor subtypes (SSTs) has not been directly assessed so far. In this study, we assessed G-protein signaling in human embryonic kidney (HEK293) cells stably expressing G protein-coupled inwardly rectifying potassium (GIRK) channels and SSTs using a novel fluorescence-based membrane potential assay. Dose-response curves obtained for veldoreotide revealed high potency and efficacy in cells expressing SST2, SST4, and SST5. Veldoreotide also inhibited proliferation and chromogranin A secretion in SST4-transfected BON-1 cells. In addition, we assessed G-protein signaling in primary pituitary cultures from SST2 and SST5 knockout mice. Our results show that octreotide mediates its effects selectively via the SST2 receptor. Conversely, pasireotide mediates its effects selectively via the SST5 receptor. In contrast, veldoreotide can activate both SST2 and SST5 receptors under otherwise identical conditions. Thus, veldoreotide is a unique SSA with full agonistic activity at the SST2, SST4, and SST5 receptors.

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.

scholarly journals Every Detail Matters. That Is, How the Interaction between Gα Proteins and Membrane Affects Their Function

Membranes ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 222
Author(s):  
Agnieszka Polit ◽  
Paweł Mystek ◽  
Ewa Błasiak
Keyword(s):  
Signal Transduction ◽  
G Protein ◽  
G Proteins ◽  
Lipid Membranes ◽  
Signaling Proteins ◽  
Heterotrimeric G Proteins ◽  
Membrane Attachment ◽  
The Individual ◽  
Multicellular Organisms ◽  
G Protein Coupled

In highly organized multicellular organisms such as humans, the functions of an individual cell are dependent on signal transduction through G protein-coupled receptors (GPCRs) and subsequently heterotrimeric G proteins. As most of the elements belonging to the signal transduction system are bound to lipid membranes, researchers are showing increasing interest in studying the accompanying protein–lipid interactions, which have been demonstrated to not only provide the environment but also regulate proper and efficient signal transduction. The mode of interaction between the cell membrane and G proteins is well known. Despite this, the recognition mechanisms at the molecular level and how the individual G protein-membrane attachment signals are interrelated in the process of the complex control of membrane targeting of G proteins remain unelucidated. This review focuses on the mechanisms by which mammalian Gα subunits of G proteins interact with lipids and the factors responsible for the specificity of membrane association. We summarize recent data on how these signaling proteins are precisely targeted to a specific site in the membrane region by introducing well-defined modifications as well as through the presence of polybasic regions within these proteins and interactions with other components of the heterocomplex.

scholarly journals Rgs4 is a regulator of mTOR activity required for motoneuron axon outgrowth and neuronal development in zebrafish

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Aya Mikdache ◽  
Marie-José Boueid ◽  
Lorijn van der Spek ◽  
Emilie Lesport ◽  
Brigitte Delespierre ◽  
...  
Keyword(s):  
Nervous System ◽  
G Protein ◽  
Neural Development ◽  
Neuronal Development ◽  
Axon Outgrowth ◽  
Rgs Proteins ◽  
Protein Signaling ◽  
Loss Of Function ◽  
G Protein Coupled

AbstractThe Regulator of G protein signaling 4 (Rgs4) is a member of the RGS proteins superfamily that modulates the activity of G-protein coupled receptors. It is mainly expressed in the nervous system and is linked to several neuronal signaling pathways; however, its role in neural development in vivo remains inconclusive. Here, we generated and characterized a rgs4 loss of function model (MZrgs4) in zebrafish. MZrgs4 embryos showed motility defects and presented reduced head and eye sizes, reflecting defective motoneurons axon outgrowth and a significant decrease in the number of neurons in the central and peripheral nervous system. Forcing the expression of Rgs4 specifically within motoneurons rescued their early defective outgrowth in MZrgs4 embryos, indicating an autonomous role for Rgs4 in motoneurons. We also analyzed the role of Akt, Erk and mechanistic target of rapamycin (mTOR) signaling cascades and showed a requirement for these pathways in motoneurons axon outgrowth and neuronal development. Drawing on pharmacological and rescue experiments in MZrgs4, we provide evidence that Rgs4 facilitates signaling mediated by Akt, Erk and mTOR in order to drive axon outgrowth in motoneurons and regulate neuronal numbers.

scholarly journals Selection of the First 99mTc-Labelled Somatostatin Receptor Subtype 2 Antagonist for Clinical Translation—Preclinical Assessment of Two Optimized Candidates

2020 ◽  
Vol 14 (1) ◽  
pp. 19
Author(s):  
Melpomeni Fani ◽  
Viktoria Weingaertner ◽  
Petra Kolenc Peitl ◽  
Rosalba Mansi ◽  
Raghuvir H. Gaonkar ◽  
...  
Keyword(s):  
Protein Binding ◽  
Somatostatin Receptor ◽  
Somatostatin Receptors ◽  
Preclinical Study ◽  
Clinical Translation ◽  
Hek293 Cells ◽  
Neuroendocrine Neoplasms ◽  
Receptor Subtype ◽  
Selection Of

Recently, radiolabelled antagonists targeting somatostatin receptors subtype 2 (SST2) in neuroendocrine neoplasms demonstrated certain superior properties over agonists. Within the ERA-PerMED project “TECANT” two 99mTc-Tetramine (N4)-derivatized SST2 antagonists (TECANT-1 and TECANT-2) were studied for the selection of the best candidate for clinical translation. Receptor-affinity, internalization and dissociation studies were performed in human embryonic kidney-293 (HEK293) cells transfected with the human SST2 (HEK-SST2). Log D, protein binding and stability in human serum were assessed. Biodistribution and SPECT/CT studies were carried out in nude mice bearing HEK-SST2 xenografts, together with dosimetric estimations from mouse-to-man. [99mTc]Tc-TECANT-1 showed higher hydrophilicity and lower protein binding than [99mTc]-TECANT-2, while stability was comparable. Both radiotracers revealed similar binding affinity, while [99mTc]Tc-TECANT-1 had higher cellular uptake (>50%, at 2 h/37 °C) and lower dissociation rate (<30%, at 2 h/37 °C). In vivo, [99mTc]Tc-TECANT-1 showed lower blood values, kidney and muscles uptake, whereas tumour uptake was comparable to [99mTc]Tc-TECANT-2. SPECT/CT imaging confirmed the biodistribution results, providing the best tumour-to-background image contrast for [99mTc]Tc-TECANT-1 at 4 h post-injection (p.i.). The estimated radiation dose amounted to approximately 6 µSv/MBq for both radiotracers. This preclinical study provided the basis of selection of [99mTc]Tc-TECANT-1 for clinical translation of the first 99mTc-based SST2 antagonist.

Lysophosphatidylinositol: a novel link between ABC transporters and G-protein-coupled receptors

2014 ◽  
Vol 42 (5) ◽  
pp. 1372-1377 ◽  
Author(s):  
Emily L. Ruban ◽  
Riccardo Ferro ◽  
Syamsul Ahmad Arifin ◽  
Marco Falasca
Keyword(s):  
Cell Proliferation ◽  
G Protein ◽  
Cancer Progression ◽  
Multidrug Resistance Protein 1 ◽  
Autocrine Loop ◽  
Cell Functions ◽  
Cytosolic Phospholipase ◽  
Signalling Cascades ◽  
Novel Strategy ◽  
G Protein Coupled

Lysophosphatidylinositol (LPI) is a well-known bioactive lipid that is able to activate signalling cascades relevant to cell proliferation, migration, survival and tumorigenesis. Our previous work suggested that LPI is involved in cancer progression since it can be released in the medium of Ras-transformed fibroblasts and can function as an autocrine modulator of cell growth. Different research groups have established that LPI is the specific and functional ligand for G-protein-coupled receptor 55 (GPR55) and that this GPR55–LPI axis is able to activate signalling cascades that are relevant for different cell functions. Work in our laboratory has recently unravelled an autocrine loop, by which LPI synthesized by cytosolic phospholipase A2 (cPLA2) is pumped out of the cell by ATP-binding cassette (ABC) transporter C1 (ABCC1)/multidrug resistance protein 1 (MRP1), initiating a signalling cascade downstream of GPR55. Our current work suggests that blockade of this pathway may represent a novel strategy to inhibit cancer cell proliferation.

A generic microfluidic biosensor of G protein-coupled receptor activation – impedance measurements of reversible morphological changes of reverse transfected HEK293 cells on microelectrodes

RSC Advances ◽  
2015 ◽  
Vol 5 (65) ◽  
pp. 52563-52570 ◽  
Author(s):  
Saurabh K. Srivastava ◽  
Rajesh Ramaneti ◽  
Margriet Roelse ◽  
Hien Duy Tong ◽  
Elwin X. Vrouwe ◽  
...  
Keyword(s):  
G Protein ◽  
Morphological Changes ◽  
Receptor Activation ◽  
Membrane Receptors ◽  
Hek293 Cells ◽  
G Protein Coupled Receptor ◽  
Impedance Measurements ◽  
Transfected Cells ◽  
Microfluidic Biosensor ◽  
G Protein Coupled

Flowcell with micro-IDEs (250–500 μm) covered with both stable and reverse transfected cells overexpressing membrane receptors to demonstrate impedance responses to serial injections of analyte.

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