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Kumar U. Somatostatin and Somatostatin Receptors in Tumour Biology. Int J Mol Sci 2023; 25:436. [PMID: 38203605 PMCID: PMC10779198 DOI: 10.3390/ijms25010436] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2023] [Revised: 12/24/2023] [Accepted: 12/25/2023] [Indexed: 01/12/2024] Open
Abstract
Somatostatin (SST), a growth hormone inhibitory peptide, is expressed in endocrine and non-endocrine tissues, immune cells and the central nervous system (CNS). Post-release from secretory or immune cells, the first most appreciated role that SST exhibits is the antiproliferative effect in target tissue that served as a potential therapeutic intervention in various tumours of different origins. The SST-mediated in vivo and/or in vitro antiproliferative effect in the tumour is considered direct via activation of five different somatostatin receptor subtypes (SSTR1-5), which are well expressed in most tumours and often more than one receptor in a single cell. Second, the indirect effect is associated with the regulation of growth factors. SSTR subtypes are crucial in tumour diagnosis and prognosis. In this review, with the recent development of new SST analogues and receptor-specific agonists with emerging functional consequences of signaling pathways are promising therapeutic avenues in tumours of different origins that are discussed.
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Affiliation(s)
- Ujendra Kumar
- Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, BC V6T 1Z3, Canada
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Targeting GPCRs and Their Signaling as a Therapeutic Option in Melanoma. Cancers (Basel) 2022; 14:cancers14030706. [PMID: 35158973 PMCID: PMC8833576 DOI: 10.3390/cancers14030706] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2022] [Revised: 01/27/2022] [Accepted: 01/27/2022] [Indexed: 12/10/2022] Open
Abstract
Simple Summary Sixteen G-protein-coupled receptors (GPCRs) have been involved in melanogenesis or melanomagenesis. Here, we review these GPCRs, their associated signaling, and therapies. Abstract G-protein-coupled receptors (GPCRs) serve prominent roles in melanocyte lineage physiology, with an impact at all stages of development, as well as on mature melanocyte functions. GPCR ligands are present in the skin and regulate melanocyte homeostasis, including pigmentation. The role of GPCRs in the regulation of pigmentation and, consequently, protection against external aggression, such as ultraviolet radiation, has long been established. However, evidence of new functions of GPCRs directly in melanomagenesis has been highlighted in recent years. GPCRs are coupled, through their intracellular domains, to heterotrimeric G-proteins, which induce cellular signaling through various pathways. Such signaling modulates numerous essential cellular processes that occur during melanomagenesis, including proliferation and migration. GPCR-associated signaling in melanoma can be activated by the binding of paracrine factors to their receptors or directly by activating mutations. In this review, we present melanoma-associated alterations of GPCRs and their downstream signaling and discuss the various preclinical models used to evaluate new therapeutic approaches against GPCR activity in melanoma. Recent striking advances in our understanding of the structure, function, and regulation of GPCRs will undoubtedly broaden melanoma treatment options in the future.
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Patel M, Tena I, Jha A, Taieb D, Pacak K. Somatostatin Receptors and Analogs in Pheochromocytoma and Paraganglioma: Old Players in a New Precision Medicine World. Front Endocrinol (Lausanne) 2021; 12:625312. [PMID: 33854479 PMCID: PMC8039528 DOI: 10.3389/fendo.2021.625312] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Accepted: 03/04/2021] [Indexed: 12/16/2022] Open
Abstract
Neuroendocrine tumors overexpress somatostatin receptors, which serve as important and unique therapeutic targets for well-differentiated advanced disease. This overexpression is a well-established finding in gastroenteropancreatic neuroendocrine tumors which has guided new medical therapies in the administration of somatostatin analogs, both "cold", particularly octreotide and lanreotide, and "hot" analogs, chelated to radiolabeled isotopes. The binding of these analogs to somatostatin receptors effectively suppresses excess hormone secretion and tumor cell proliferation, leading to stabilization, and in some cases, tumor shrinkage. Radioisotope-labeled somatostatin analogs are utilized for both tumor localization and peptide radionuclide therapy, with 68Ga-DOTATATE and 177Lu-DOTATATE respectively. Benign and malignant pheochromocytomas and paragangliomas also overexpress somatostatin receptors, irrespective of embryological origin. The pattern of somatostatin receptor overexpression is more prominent in succinate dehydrogenase subunit B gene mutation, which is more aggressive than other subgroups of this disease. While the Food and Drug Administration has approved the use of 68Ga-DOTATATE as a radiopharmaceutical for somatostatin receptor imaging, the use of its radiotherapeutic counterpart still needs approval beyond gastroenteropancreatic neuroendocrine tumors. Thus, patients with pheochromocytoma and paraganglioma, especially those with inoperable or metastatic diseases, depend on the clinical trials of somatostatin analogs. The review summarizes the advances in the utilization of somatostatin receptor for diagnostic and therapeutic approaches in the neuroendocrine tumor subset of pheochromocytoma and paraganglioma; we hope to provide a positive perspective in using these receptors as targets for treatment in this rare condition.
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Affiliation(s)
- Mayank Patel
- Section on Medical Neuroendocrinology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, United States
| | - Isabel Tena
- Scientific Department, Medica Scientia Innovation Research (MedSIR), Barcelona, Spain
- Section of Medical Oncology, Consorcio Hospitalario Provincial of Castellon, Castellon, Spain
| | - Abhishek Jha
- Section on Medical Neuroendocrinology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, United States
| | - David Taieb
- Department of Nuclear Medicine, La Timone University Hospital, CERIMED, Aix-Marseille University, Marseille, France
| | - Karel Pacak
- Section on Medical Neuroendocrinology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, United States
- *Correspondence: Karel Pacak,
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Abstract
Morbidity and mortality rates in patients with active acromegaly are higher than the general population. Adequate biochemical control restores mortality to normal rates. Now, medical therapy has an increasingly important role in the treatment of patients with acromegaly. Somatostatin receptor ligands (SRLs) are considered the standard medical therapy, either after surgery or as a first-line therapy when surgery is deemed ineffective or is contraindicated. Overall, octreotide and lanreotide are first-generation SRLs and are effective in ~20%-70% of patients. Pegvisomant, a growth hormone receptor antagonist, controls insulin-like growth factor 1 in 65%-90% of cases. Consequently, a subset of patients (nonresponders) requires other treatment options. Drug combination therapy offers the potential for more efficacious disease control. However, the development of new medical therapies remains essential. Here, emphasis is placed on new medical therapies to control acromegaly. There is a focus on pasireotide long-acting release (LAR) (Signifor LAR®), which was approved in 2014 by the US Food and Drug Administration and the European Medicine Agency for the treatment of acromegaly. Pasireotide LAR is a long-acting somatostatin multireceptor ligand. In a Phase III clinical trial in patients with acromegaly (naïve to medical therapy or uncontrolled on a maximum dose of first-generation SRLs), 40 and 60 mg of intramuscular pasireotide LAR achieved better biochemical disease control than octreotide LAR, and tumor shrinkage was noted in both pasireotide groups. Pasireotide LAR tolerability was similar to other SRLs, except for a greater frequency and degree of hyperglycemia and diabetes mellitus. Baseline glucose may predict hyperglycemia occurrence after treatment, and careful monitoring of glycemic status and appropriate treatment is required. A precise definition of patients with acromegaly who will derive the greatest therapeutic benefit from pasireotide LAR remains to be established. Lastly, novel therapies and new potential delivery modalities (oral octreotide) are summarized.
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Affiliation(s)
- Daniel Cuevas-Ramos
- Department of Endocrinology and Metabolism, Neuroendocrinology Clinic, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Mexico City, Mexico
| | - Maria Fleseriu
- Department of Medicine (Endocrinology), Portland, OR, USA
- Department of Neurological Surgery, Northwest Pituitary Center, Oregon Health & Science University, Portland, OR, USA
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Kiseljak-Vassiliades K, Xu M, Mills TS, Smith EE, Silveira LJ, Lillehei KO, Kerr JM, Kleinschmidt-DeMasters BK, Wierman ME. Differential somatostatin receptor (SSTR) 1-5 expression and downstream effectors in histologic subtypes of growth hormone pituitary tumors. Mol Cell Endocrinol 2015; 417:73-83. [PMID: 26391562 PMCID: PMC4641524 DOI: 10.1016/j.mce.2015.09.016] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/20/2015] [Revised: 09/11/2015] [Accepted: 09/17/2015] [Indexed: 12/27/2022]
Abstract
PURPOSE The aim of this study was to examine whether differential expression of somatostatin receptors (SSTR) 1-5 and downstream effectors are different in densely (DG) and sparsely (SG) granulated histological growth hormone (GH) pituitary tumor subtypes. METHODS The study included 33 acromegalic patients with 23 DG and 10 SG tumors. SSTR1-5 were measured by qPCR and immunoblotting. Signaling candidates downstream of SSTR2 were also assessed. RESULTS SSTR2 mRNA and protein levels were significantly higher in DG compared to SG tumors. Downstream of SSTR2, p27(kip1) was decreased (2.6-fold) in SG compared to DG tumors, suggesting a potential mechanism of SSA resistance in SG tumors with intact SSTR2 expression. Re-expression of E-cadherin in GH pituitary cell increased p27(kip1) levels. CONCLUSIONS Histological subtyping correlated with SSTR2, E cadherin and p27(kip) protein levels and these may serve as useful biomarkers in GH tumors to predict behavior and response to therapy with SSA.
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Affiliation(s)
- Katja Kiseljak-Vassiliades
- Division of Endocrinology, Metabolism and Diabetes, Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA; Research Service Veterans Affairs Medical Center, Denver, CO 80220, USA.
| | - Mei Xu
- Division of Endocrinology, Metabolism and Diabetes, Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Taylor S Mills
- Division of Endocrinology, Metabolism and Diabetes, Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Elizabeth E Smith
- Department of Pathology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Lori J Silveira
- Division of Biostatistics and Bioinformatics, National Jewish Health, Denver, CO 80206, USA
| | - Kevin O Lillehei
- Department of Neurosurgery, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Janice M Kerr
- Division of Endocrinology, Metabolism and Diabetes, Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - B K Kleinschmidt-DeMasters
- Department of Pathology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA; Department of Neurosurgery, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Margaret E Wierman
- Division of Endocrinology, Metabolism and Diabetes, Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA; Research Service Veterans Affairs Medical Center, Denver, CO 80220, USA
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Role of somatostatin receptor-2 in gentamicin-induced auditory hair cell loss in the Mammalian inner ear. PLoS One 2014; 9:e108146. [PMID: 25268135 PMCID: PMC4182454 DOI: 10.1371/journal.pone.0108146] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Accepted: 08/18/2014] [Indexed: 01/10/2023] Open
Abstract
Hair cells and spiral ganglion neurons of the mammalian auditory system do not regenerate, and their loss leads to irreversible hearing loss. Aminoglycosides induce auditory hair cell death in vitro, and evidence suggests that phosphatidylinositol-3-kinase/Akt signaling opposes gentamicin toxicity via its downstream target, the protein kinase Akt. We previously demonstrated that somatostatin-a peptide with hormone/neurotransmitter properties-can protect hair cells from gentamicin-induced hair cell death in vitro, and that somatostatin receptors are expressed in the mammalian inner ear. However, it remains unknown how this protective effect is mediated. In the present study, we show a highly significant protective effect of octreotide (a drug that mimics and is more potent than somatostatin) on gentamicin-induced hair cell death, and increased Akt phosphorylation in octreotide-treated organ of Corti explants in vitro. Moreover, we demonstrate that somatostatin receptor-1 knockout mice overexpress somatostatin receptor-2 in the organ of Corti, and are less susceptible to gentamicin-induced hair cell loss than wild-type or somatostatin-1/somatostatin-2 double-knockout mice. Finally, we show that octreotide affects auditory hair cells, enhances spiral ganglion neurite number, and decreases spiral ganglion neurite length.
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Cuevas-Ramos D, Fleseriu M. Somatostatin receptor ligands and resistance to treatment in pituitary adenomas. J Mol Endocrinol 2014; 52:R223-40. [PMID: 24647046 DOI: 10.1530/jme-14-0011] [Citation(s) in RCA: 113] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Somatostatin (SST), an inhibitory polypeptide with two biologically active forms SST14 and SST28, inhibits GH, prolactin (PRL), TSH, and ACTH secretion in the anterior pituitary gland. SST also has an antiproliferative effect inducing cell cycle arrest and apoptosis. Such actions are mediated through five G-protein-coupled somatostatin receptors (SSTR): SSTR1-SSTR5. In GH-secreting adenomas, SSTR2 expression predominates, and somatostatin receptor ligands (SRLs; octreotide and lanreotide) directed to SSTR2 are presently the mainstays of medical therapy. However, about half of patients show incomplete biochemical remission, but the definition of resistance per se remains controversial. We summarize here the determinants of SRL resistance in acromegaly patients, including clinical, imaging features as well as molecular (mutations, SSTR variants, and polymorphisms), and histopathological (granulation pattern, and proteins and receptor expression) predictors. The role of SSTR5 may explain the partial responsiveness to SRLs in patients with adequate SSTR2 density in the cell membrane. In patients with ACTH-secreting pituitary adenomas, i.e. Cushing's disease (CD), SSTR5 is the most abundant receptor expressed and tumors show low SSTR2 density due to hypercortisolism-induced SSTR2 down-regulation. Clinical studies with pasireotide, a multireceptor-targeted SRL with increased SSTR5 activity, lead to approval of pasireotide for treatment of patients with CD. Other SRL delivery modes (oral octreotide), multireceptor-targeted SRL (somatoprim) or chimeric compounds targeting dopamine D2 receptors and SSTR2 (dopastatin), are briefly discussed.
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Affiliation(s)
- Daniel Cuevas-Ramos
- Department of MedicinePituitary Center, Cedars-Sinai Medical Center, Los Angeles, California, USANorthwest Pituitary Center and Departments of Medicine and Neurological SurgeryOregon Health and Science University, 3181 SW Sam Jackson Park Road (BTE 472), Portland, Oregon 97239, USA
| | - Maria Fleseriu
- Department of MedicinePituitary Center, Cedars-Sinai Medical Center, Los Angeles, California, USANorthwest Pituitary Center and Departments of Medicine and Neurological SurgeryOregon Health and Science University, 3181 SW Sam Jackson Park Road (BTE 472), Portland, Oregon 97239, USA
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Theodoropoulou M, Stalla GK. Somatostatin receptors: from signaling to clinical practice. Front Neuroendocrinol 2013; 34:228-52. [PMID: 23872332 DOI: 10.1016/j.yfrne.2013.07.005] [Citation(s) in RCA: 241] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/28/2013] [Revised: 06/13/2013] [Accepted: 07/12/2013] [Indexed: 02/08/2023]
Abstract
Somatostatin is a peptide with a potent and broad antisecretory action, which makes it an invaluable drug target for the pharmacological management of pituitary adenomas and neuroendocrine tumors. Somatostatin receptors (SSTR1, 2A and B, 3, 4 and 5) belong to the G protein coupled receptor family and have a wide expression pattern in both normal tissues and solid tumors. Investigating the function of each SSTR in several tumor types has provided a wealth of information about the common but also distinct signaling cascades that suppress tumor cell proliferation, survival and angiogenesis. This provided the rationale for developing multireceptor-targeted somatostatin analogs and combination therapies with signaling-targeted agents such as inhibitors of the mammalian (or mechanistic) target of rapamycin (mTOR). The ability of SSTR to internalize and the development of rabiolabeled somatostatin analogs have improved the diagnosis and treatment of neuroendocrine tumors.
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Affiliation(s)
- Marily Theodoropoulou
- Department of Endocrinology, Max Planck Institute of Psychiatry, Kraepelinstrasse 10, 80804 Munich, Germany.
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Annunziata M, Luque RM, Durán-Prado M, Baragli A, Grande C, Volante M, Gahete MD, Deltetto F, Camanni M, Ghigo E, Castaño JP, Granata R. Somatostatin and somatostatin analogues reduce PDGF-induced endometrial cell proliferation and motility. Hum Reprod 2012; 27:2117-29. [PMID: 22588000 DOI: 10.1093/humrep/des144] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND Endometriosis is characterized by ectopic implantation of endometrial cells, which show increased proliferation and migration. Somatostatin (SST) and its analogues inhibit normal and cancer cell growth and motility through the SST receptors, sst1-5. Cortistatin (CST), which displays high structural and functional homology with SST, binds all ssts, as well as MrgX2. Our objective was to investigate the gene expression of the SST/CST system and to determine the effect of SST and its analogues on platelet-derived growth factor (PDGF)-induced proliferation and motility in telomerase-immortalized human endometrial stromal cell (T HESC) line and in primary endometrial stromal cell (ESCs) isolated from human endometriotic tissues. METHODS Ectopic endometrial tissues were collected from women (n= 23) undergoing laparoscopic surgery for endometriosis (Stage III/IV). Gene expression was evaluated by real-time PCR, cell motility by wound healing assay, protein expression and β-actin rearrangement by immunofluorescence, cell proliferation by the Alamar blue assay and ERK1/2 and Akt phosphorylation by western blot. RESULTS Human endometriotic tissues, primary ESCs and T HESCs expressed SST, CST and ssts. SST, its analogues SOM230 and octreotide, as well as CST, counteracted PDGF-induced proliferation and migration in both ESCs and T HESCs. SST also inhibited vascular endothelial growth factor and metalloprotease-2 mRNA expression, and reduced basal and PDGF-induced ERK1/2 phosphorylation. CONCLUSION These results indicate that the SST/CST system is expressed in endometriotic tissues and cells. The inhibitory effects of SST and its analogues on PDGF-induced proliferation and motility suggest that these peptides may represent promising tools in the treatment of endometriosis.
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Affiliation(s)
- Marta Annunziata
- Laboratory of Molecular and Cellular Endocrinology, Department of Internal Medicine, University of Turin, Corso Dogliotti 14, 10126 Turin, Italy
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Parapuram SK, Shi-wen X, Elliott C, Welch ID, Jones H, Baron M, Denton CP, Abraham DJ, Leask A. Loss of PTEN expression by dermal fibroblasts causes skin fibrosis. J Invest Dermatol 2011; 131:1996-2003. [PMID: 21654839 DOI: 10.1038/jid.2011.156] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Fibrosis represents a common pathway leading to organ failure and death in many diseases and has no effective therapy. Dysregulated repair and excessive tissue scarring provides a unifying mechanism for pathological fibrosis. The protein phosphatase and tensin homolog (PTEN) acts to dephosphorylate proteins, which promotes tissue repair and thus could be a key fibrogenic mediator. To test this hypothesis, we first showed that PTEN expression was reduced in skin fibroblasts from patients with the fibrotic autoimmune disease diffuse systemic sclerosis (dSSc). To evaluate whether this deficiency could be sufficient for fibrogenesis in vivo, we deleted PTEN in adult mouse fibroblasts. Compared with littermate control mice, loss of PTEN resulted in a 3-fold increase in dermal thickness due to excess deposition of collagen. PTEN-deleted fibroblasts showed elevated Akt phosphorylation and increased expression of connective tissue growth factor (CTGF/CCN2). Selective inhibition of the phosphatidylinositol 3-kinase/Akt pathway reduced the overexpression of collagen and CCN2 by PTEN-deficient fibroblasts. Overexpression of PTEN reduced the overexpression of type I collagen and CCN2 by dSSc fibroblasts. Thus, PTEN appears to be a potential in vivo master regulator of fibrogenesis; PTEN agonists may represent anti-fibrotic treatments.
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Affiliation(s)
- Sunil K Parapuram
- Department of Dentistry, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
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Sun L, Wang S, Hu C, Zhang X. Down-regulation of PKHD1 induces cell apoptosis through PI3K and NF-κB pathways. Exp Cell Res 2011; 317:932-40. [DOI: 10.1016/j.yexcr.2011.01.025] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2010] [Revised: 01/06/2011] [Accepted: 01/30/2011] [Indexed: 12/26/2022]
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Abstract
Somatostatin analogs (SA) are widely used in acromegaly, either as first-line or adjuvant treatment after surgery. First-line treatment with these drugs is generally used in the patients with macroadenomas or in those with clinical conditions so severe as to prevent unsafe reactions during anesthesia. Generally, the response to SA takes into account both control of GH and IGF-I excess, with consequent improvement of clinical symptoms directly related to GH and IGF-I excess, and tumor shrinkage. This latter effect is more prominent in the patients treated first-line and bearing large macroadenomas, but it is also observed in patients with microadenomas, even with little clinical implication. Predictors of response are patients' gender, age, initial GH and IGF-I levels, and tumor mass, as well as adequate expression of somatostatin receptor types 2 and 5, those with the highest affinity for octreotide and lanreotide. Only sporadic cases of somatostatin receptor gene mutation or impaired signaling pathways have been described in GH-secreting tumors so far. The response to SA also depends on treatment duration and dosage of the drug used, so that a definition of resistance based on short-term treatments using low doses of long-acting SA is limited. Current data suggest that response to these drugs is better analyzed taking together biochemical and tumoral effects because only the absence of both responses might be considered as a poor response or resistance. This latter evidence seems to occur in 25% of treated patients after 12 months of currently available long-acting SA.
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Affiliation(s)
- Annamaria Colao
- Department of Clinical and Molecular Endocrinology and Oncology, University “Federico II,” Naples, Italy.
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Wang C, Xu H, Chen H, Li J, Zhang B, Tang C, Ghishan FK. Somatostatin stimulates intestinal NHE8 expression via p38 MAPK pathway. Am J Physiol Cell Physiol 2010; 300:C375-82. [PMID: 21106692 DOI: 10.1152/ajpcell.00421.2010] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Diarrhea is a common manifestation of gastrointestinal disorders. Diarrhea-induced losses of fluid and electrolyte could lead to dehydration and electrolyte imbalances, resulting in significant morbidity and mortality, especially in children living in developing countries. Somatostatin, a peptide hormone secreted by D-cells, plays an important role in regulating motility and intestinal Na(+) absorption. Although octreotide, a somatostatin analog, is used to treat diarrhea, its mechanisms of action are unclear. Here we showed that octreotide increased brush-border membrane Na(+)/H(+) exchanger 8 (NHE8) expression in the small intestine to the exclusion of other NHEs that participate in Na(+) absorption. The same effect also occurred in human intestinal cells (Caco-2). We found that the increase of NHE8 expression by somatostatin required p38 mitogen-activated protein kinase (MAPK) activation. Furthermore, the somatostatin receptor SSTR2 antagonist CYN154806 could abolish somatostatin-induced NHE8 expression and p38 MAPK phosphorylation. Thus our data provided the first concrete evidence indicating that somatostatin stimulates intestinal Na(+) absorption by increasing intestinal NHE8 expression through the SSTR2-p38 MAPK pathway.
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Affiliation(s)
- Chunhui Wang
- Department of Gastroenterology, West China Hospital, Sichuan University, Chengdu, China
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Affiliation(s)
- Ujendra Kumar
- Faculty of Pharmaceutical Sciences, Department of Pharmacology and Toxicology, University of British Columbia, Vancouver, BC, V6T 1Z3, Canada.
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Msaouel P, Galanis E, Koutsilieris M. Somatostatin and somatostatin receptors: implications for neoplastic growth and cancer biology. Expert Opin Investig Drugs 2010; 18:1297-316. [PMID: 19678799 DOI: 10.1517/13543780903176399] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Somatostatin agonists (SM-As) are capable of achieving durable symptomatic relief and significant clinical responses in certain tumours. Herein, we review the diverse direct and indirect mechanisms of antineoplastic activity elicited by SM-As as well as the hurdles that complicate their use as monotherapies in a broader range of malignancies. Emphasis is placed on recent clinical attempts to neutralise the IGF-mediated survival factor effects in the bone metastasis microenvironment in advanced prostate cancer. The first clinical trials of this 'anti-survival factor manipulation' strategy utilised the ability of SM-As to suppress the growth hormone-dependent liver-derived IGF-I bioavailability in combination with other drugs, such as dexamethasone, zolendronate and oestrogens, acting systemically and at the bone metastasis microenvironment. These regimens restored androgen ablation responsiveness in stage D3 prostate cancer patients and successfully produced objective clinical responses while only mild toxicities were observed. Furthermore, we focus on the preclinical experimental data of a targeted SM-A coupled to the super-potent doxorubicin derivative AN-201. The resulting conjugate (AN-238) has shown increased antitumour potency with a favourable toxicity profile. The potential use of novel SM-As as anticancer drugs is discussed in relation to data suggesting other direct and indirect treatment approaches pertaining to the somatostatin system.
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Affiliation(s)
- Pavlos Msaouel
- National & Kapodistrian University of Athens, Medical School, Department of Experimental Physiology, 75 Micras Asias St, Goudi-Athens 11527, Greece
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Liu J, Damon M, Guitton N, Guisle I, Ecolan P, Vincent A, Cherel P, Gondret F. Differentially-expressed genes in pig Longissimus muscles with contrasting levels of fat, as identified by combined transcriptomic, reverse transcription PCR, and proteomic analyses. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2009; 57:3808-3817. [PMID: 19296579 DOI: 10.1021/jf8033144] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Intramuscular fat content is important for many meat quality parameters. This work is aimed at identifying functional categories of genes associated with natural variation among individuals in intramuscular fat content to help the design of genetic schemes for high marbling potential. Taking advantage of the global nature of transcriptomic and proteomic technologies, 40 genes were identified as differently expressed between high fat and low fat pig Longissimus muscles at slaughter weight. They are involved in metabolic processes, cell communication, binding, and response to stimulus. Using real-time PCR in muscle biopsies taken earlier in the fattening period, the group with a high intramuscular fat content was also characterized by the down-expression of genes playing a negative role in adipogenesis, such as architectural transcription factor high-motility hook A1, mitogen activated protein-kinase14, and cyclin D1. These results suggest that interindividual variability in intramuscular fat content might arise essentially from differences in early adipogenesis.
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Affiliation(s)
- Jingshun Liu
- INRA, UMR1079 Systèmes d'Elevage Nutrition Animale et Humaine, 35590 Saint Gilles, France
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Somatostatin receptors 1 and 5 heterodimerize with epidermal growth factor receptor: agonist-dependent modulation of the downstream MAPK signalling pathway in breast cancer cells. Cell Signal 2008; 21:428-39. [PMID: 19070659 DOI: 10.1016/j.cellsig.2008.11.012] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2008] [Revised: 11/13/2008] [Accepted: 11/15/2008] [Indexed: 12/22/2022]
Abstract
The role of somatostatin (SST) and epidermal growth factor (EGF) in breast cancer is undisputed; however, the molecular mechanisms underlying their antiproliferative or proliferative effects are not well understood. We initially confirmed that breast tumour tissues express all five somatostatin receptors (SSTR1-5) and four epidermal growth factor receptors (ErbB1-4). Subsequently, to gain insight into the function of SSTRs and ErbBs in oestrogen receptor (ER)-positive (MCF-7) or ERalpha-negative (MDA-MB-231) breast cancer cells, we defined SSTR1, SSTR5 and ErbB1 mRNA and protein expression in these two tumour cell lines. Consistent with previous studies showing SSTR1/SSTR5 heterodimerization and having seen cell-specific and ligand-selective alterations in receptor expression, we next elucidated whether SSTR1 and SSTR5 functionally interact with ErbB1 using pbFRET analysis. We subsequently determined the effects of SST and EGF either alone, or in combination, on selected downstream signalling molecules such as erk1/2, p38 and JNK. Here, we showed that both SST and EGF influenced erk1/2 phosphorylation and that SST modulated the effects of EGF in a cell-specific manner. We also demonstrated agonist-, time and cell-dependent regulation of p38 phosphorylation. We further investigated modulation of Grb2, SOS, Shc, SH-PTP1 and SH-PTP2. ErbB1 adaptor proteins known to play a role in MAPK activation, Shc, Grb2 and SOS, changed in an agonist- and cell-specific manner whereas, SH-PTP1 and SH-PTP2, adaptor proteins reported to interact with SSTRs, translocated from the cytosol to membrane in a cell-specific manner following SST and/or EGF treatment. Although several previous studies have shown crosstalk between RTKs and GPCRs, there are no reports describing SSTR (GPCR) modulation of ErbBs (RTK) in breast cancer. To the best of our knowledge, this is the first report describing crosstalk/interactions between SSTRs and ErbBs.
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18
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Ryall JG, Lynch GS. The potential and the pitfalls of β-adrenoceptor agonists for the management of skeletal muscle wasting. Pharmacol Ther 2008; 120:219-32. [DOI: 10.1016/j.pharmthera.2008.06.003] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2008] [Accepted: 06/04/2008] [Indexed: 01/08/2023]
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19
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New DC, Wu K, Kwok AWS, Wong YH. G protein-coupled receptor-induced Akt activity in cellular proliferation and apoptosis. FEBS J 2007; 274:6025-36. [PMID: 17949438 DOI: 10.1111/j.1742-4658.2007.06116.x] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Akt (also known as protein kinase B) plays an integral role in many intracellular signaling pathways activated by a diverse array of extracellular signals that target several different classes of membrane-bound receptors. Akt plays a particularly prominent part in signaling networks that result in the modulation of cellular proliferation, apoptosis and survival. Thus, the overexpression of Akt subtypes has been measured in a number of cancer types, and dominant-negative forms of Akt can trigger apoptosis and reduce the survival of cancer cells. G protein-coupled receptors act as cell-surface detectors for a diverse spectrum of biological signals and are able to activate or inhibit Akt via several direct and indirect means. In this review, we shall document how G protein-coupled receptors are able to control Akt activity and examine the resulting biochemical and physiological changes, with particular emphasis on cellular proliferation, apoptosis and survival.
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Affiliation(s)
- David C New
- Department of Biochemistry, Molecular Neuroscience Center, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
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20
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Yang SK, Chen C. Involvement of somatostatin receptor subtypes in membrane ion channel modification by somatostatin in pituitary somatotropes. Clin Exp Pharmacol Physiol 2007; 34:1221-7. [PMID: 17892506 DOI: 10.1111/j.1440-1681.2007.04806.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
1. Growth hormone (GH) secretion from pituitary somatotropes is mainly regulated by two hypothalamic hormones, GH-releasing hormone (GHRH) and somatotrophin releasing inhibitory factor (SRIF). 2. Somatotrophin releasing inhibitory factor inhibits GH secretion via activation of specific membrane receptors, somatostatin receptors (SSTRs) and signalling transduction systems in somatotropes. 3. Five subtypes of SSTRs, namely SSTR1, 2, 3, 4 and 5, have been identified, with the SSTR2 subtype divided into SSTR2A and SSTR2B. All SSTRs are G-protein-coupled receptors. 4. Voltage-gated Ca(2+) and K(+) channels on the somatotrope membrane play an important role in regulating GH secretion and SRIF modifies both channels to reduce intracellular free Ca(2+) concentration and GH secretion. 5. Using specific SSTR subtype-specific agonists, it has been found that reduction in Ca(2+) currents by SRIF is mediated by SSTR2 and an increase in K(+) currents is mediated by both SSTR2 and SSTR4 in rat somatotropes.
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Affiliation(s)
- Seung-Kwon Yang
- Prince Henry's Institute of Medical Research, Clayton, Victoria, Australia
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21
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Stafford MR, Bartlett PF, Adams DJ. Purinergic receptor activation inhibits mitogen-stimulated proliferation in primary neurospheres from the adult mouse subventricular zone. Mol Cell Neurosci 2007; 35:535-48. [PMID: 17553694 DOI: 10.1016/j.mcn.2007.04.013] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2007] [Revised: 04/25/2007] [Accepted: 04/30/2007] [Indexed: 11/20/2022] Open
Abstract
The expression pattern of purinergic receptors was examined in subventricular zone-derived primary neurospheres. Primary neurospheres expressed mRNA for P2X4 and P2X7 receptors, all P2Y receptors, with the exception of P2Y4, and the A1, A2a and A2b adenosine receptors. ATPgammaS, ADPbetaS and UTP evoked transient increases in cytoplasmic Ca(2+) concentration in dissociated primary neurospheres, demonstrating the functional expression of P2Y1 and P2Y2 receptors. Ca(2+) transients were not attenuated by the removal of extracellular Ca(2+) and were reversibly inhibited by the P2Y1 selective antagonist, MRS 2179. P2Y and adenosine receptor agonists reduced the size and frequency of primary neurospheres. The effects of ADPbetaS and adenosine were reversed by subtype-selective receptor antagonists, demonstrating that P2Y1 and A2a receptors mediate inhibitory effects on primary neurosphere proliferation. The modulation of neural precursor cell proliferation by P2Y and adenosine receptors therefore represents a potential regulatory mechanism within the neurogenic microenvironment.
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Affiliation(s)
- Mark R Stafford
- School of Biomedical Sciences, The University of Queensland, Brisbane 4072, Australia
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22
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New DC, Wong YH. Molecular mechanisms mediating the G protein-coupled receptor regulation of cell cycle progression. J Mol Signal 2007; 2:2. [PMID: 17319972 PMCID: PMC1808056 DOI: 10.1186/1750-2187-2-2] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2007] [Accepted: 02/26/2007] [Indexed: 12/27/2022] Open
Abstract
G protein-coupled receptors are key regulators of cellular communication, mediating the efficient coordination of a cell's responses to extracellular stimuli. When stimulated these receptors modulate the activity of a wide range of intracellular signalling pathways that facilitate the ordered development, growth and reproduction of the organism. There is now a growing body of evidence examining the mechanisms by which G protein-coupled receptors are able to regulate the expression, activity, localization and stability of cell cycle regulatory proteins that either promote or inhibit the initiation of DNA synthesis. In this review, we will detail the intracellular pathways that mediate the G protein-coupled receptor regulation of cellular proliferation, specifically the progression from the G1 phase to the S phase of the cell cycle.
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Affiliation(s)
- David C New
- Department of Biochemistry, the Molecular Neuroscience Center, and the Biotechnology Research Institute, Hong Kong University of Science and Technology, Clearwater Bay, Hong Kong, China
| | - Yung H Wong
- Department of Biochemistry, the Molecular Neuroscience Center, and the Biotechnology Research Institute, Hong Kong University of Science and Technology, Clearwater Bay, Hong Kong, China
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23
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Huang CC, You JL, Wu MY, Hsu KS. Rap1-induced p38 Mitogen-activated Protein Kinase Activation Facilitates AMPA Receptor Trafficking via the GDI·Rab5 Complex. J Biol Chem 2004; 279:12286-92. [PMID: 14709549 DOI: 10.1074/jbc.m312868200] [Citation(s) in RCA: 153] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Recent evidence has emphasized the importance of p38 mitogen-activated protein kinase (MAPK) in the induction of metabotropic glutamate receptor (mGluR)-dependent long term depression (LTD) at hippocampal CA3-CA1 synapses. However, the cascade responsible of mGluR to activate p38 MAPK and the signaling pathway immediately downstream from it to induce synaptic depression is poorly understood. Here, we show that transient activation of group I mGluR with the selective agonist (S)-3,5-dihydroxyphenylglycine (DHPG) activates p38 MAPK through G protein betagamma-subunit, small GTPase Rap1, and MAPK kinase 3/6 (MKK3/6), thus resulting in mGluR5-dependent LTD. Furthermore, our data clearly show that an accelerating AMPA receptor endocytosis by stimulating the formation of guanyl nucleotide dissociation inhibitor-Rab5 complex is a potential downstream processing of p38 MAPK activation to mediate DHPG-LTD. These results suggest an important role for Rap1-MKK3/6-p38 MAPK pathway in the induction of mGluR-dependent LTD by directly coupling to receptor trafficking machineries to facilitate the loss of synaptic AMPA receptors.
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Affiliation(s)
- Chiung-Chun Huang
- Department of Pharmacology, College of Medicine, National Cheng Kung University, No. 1 University Road, Tainan City 701, Taiwan
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24
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Weckbecker G, Lewis I, Albert R, Schmid HA, Hoyer D, Bruns C. Opportunities in somatostatin research: biological, chemical and therapeutic aspects. Nat Rev Drug Discov 2004; 2:999-1017. [PMID: 14654798 DOI: 10.1038/nrd1255] [Citation(s) in RCA: 402] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Gisbert Weckbecker
- Transplantation and Immunology, Novartis Institutes for BioMedical Research, Novartis Pharma AG, CH-4002 Basel, Switzerland.
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25
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Levchenko A. Dynamical and integrative cell signaling: challenges for the new biology. Biotechnol Bioeng 2003; 84:773-82. [PMID: 14708118 DOI: 10.1002/bit.10854] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Years of careful experimental analysis have revealed that signaling molecules are organized into complex networks of biochemical reactions exquisitely regulated in time and space to provide a cell with high-fidelity information about an extremely noisy and volatile environment. A new view of signaling networks as systems consisting of multiple complex elements interacting in a multifarious fashion is emerging, a view that conflicts with the single-gene or protein-centric approach common in biological research. The postgenomic era has brought about a different, network-centric methodology of analysis, suddenly forcing researchers toward the opposite extreme of complexity, where the networks being explored are, to a certain extent, intractable and uninterpretable. Both the cartoons of simple pathways and the very large "hair-ball" diagrams of large intracellular networks are also representations of static worlds, superficially devoid of dynamics and chemistry. These representations are often viewed as being analogous to stably linked computer and neural networks rather than dynamically changing networks of chemical interactions, where the notions of concentration, compartmentalization, and diffusion may be the primary determinants of connectivity. Arguably, the systems biology approach, relying on computational modeling coupled with various experimental techniques and methodologies, will be an essential component of analysis of the behavior of signal transduction pathways. Combining the dynamical view of rapidly evolving responses and the structural view arising from high-throughput analyses of the interacting species will be the best approach toward efforts toward greater understanding of intracellular signaling processes.
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Affiliation(s)
- Andre Levchenko
- The Whitaker Institute for Biomedical Engineering, The Johns Hopkins University, 208C Clark Hall, 3400 North Charles Street, Baltimore, Maryland 21218, USA.
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26
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Lahlou H, Saint-Laurent N, Estève JP, Eychène A, Pradayrol L, Pyronnet S, Susini C. sst2 Somatostatin receptor inhibits cell proliferation through Ras-, Rap1-, and B-Raf-dependent ERK2 activation. J Biol Chem 2003; 278:39356-71. [PMID: 12878607 DOI: 10.1074/jbc.m304524200] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The G protein-coupled sst2 somatostatin receptor is a critical negative regulator of cell proliferation. sstII prevents growth factor-induced cell proliferation through activation of the tyrosine phosphatase SHP-1 leading to induction of the cyclin-dependent kinase inhibitor p27Kip1. Here, we investigate the signaling molecules linking sst2 to p27Kip1. In Chinese hamster ovary-DG-44 cells stably expressing sst2 (CHO/sst2), the somatostatin analogue RC-160 transiently stimulates ERK2 activity and potentiates insulin-stimulated ERK2 activity. RC-160 also stimulates ERK2 activity in pancreatic acini isolated from normal mice, which endogenously express sst2, but has no effect in pancreatic acini derived from sst2 knock-out mice. RC-160-induced p27Kip1 up-regulation and inhibition of insulin-dependent cell proliferation are both prevented by pretreatment of CHO/sst2 cells with the MEK1/2 inhibitor PD98059. In addition, using dominant negative mutants, we show that sst2-mediated ERK2 stimulation is dependent on the pertussis toxin-sensitive Gi/o protein, the tyrosine kinase Src, both small G proteins Ras and Rap1, and the MEK kinase B-Raf but is independent of Raf-1. Phosphatidylinositol 3-kinase (PI3K) and both tyrosine phosphatases, SHP-1 and SHP-2, are required upstream of Ras and Rap1. Taken together, our results identify a novel mechanism whereby a Gi/o protein-coupled receptor inhibits cell proliferation by stimulating ERK signaling via a SHP-1-SHP-2-PI3K/Ras-Rap1/B-Raf/MEK pathway.
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Affiliation(s)
- Hicham Lahlou
- INSERM U531, IFR31, Centre Hospitalier Universitaire Rangueil, 1 avenue Jean Poulhès, 31403 Toulouse Cedex and CNRS Unité Mixte de Recherche 146, Institut Curie, Centre Universitaire, 91405 Orsay Cedex, France
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27
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An JJ, Cho SR, Jeong DW, Park KW, Ahn YS, Baik JH. Anti-proliferative effects and cell death mediated by two isoforms of dopamine D2 receptors in pituitary tumor cells. Mol Cell Endocrinol 2003; 206:49-62. [PMID: 12943989 DOI: 10.1016/s0303-7207(03)00236-3] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Stable rat pituitary tumor cell lines expressing two isoforms of the dopamine D2 receptor, D2L (long) and D2S (short) (the GH3D2L and GH3D2S cell lines, respectively), were established, and the signaling pathway underlying the anti-proliferative and cell death effects of dopaminergic agonists was examined in these cells. After either dopamine or quinpirole treatment, the cell viability decreased significantly only in GH3D2L cells and GH3D2S cells, but not in GH3 cells where D2 receptors are absent. Treatment with haloperidol, a specific D2 receptor antagonist, rescued the dopamine-mediated decreased cell viability in both the GH3D2L and GH3D2S cells. Treatment of these cells with dopamine decreased the DNA synthesis rate, as demonstrated by the incorporation of 5-bromo-2'-deoxyuridine (BrdU). Dopamine-induced cell death was observed in the GH3D2L and GH3D2S cells, and was accompanied by DNA laddering and caspase-3 activation, which were blunted by haloperidol, indicating that dopamine-induced cell death in these cells is mediated by the dopamine D2 receptors. D2 receptor-mediated cell death in these cells correlated with the sustained and enhanced activation of p38 mitogen-activated protein kinase (MAPK) and the extracellular-signal regulated kinase (ERK)1/2 pathways. Treatment with SB203580, which is a specific p38 MAPK inhibitor and PD98059, which is an inhibitor of MEK1/ERK signaling, selectively abrogates dopamine-induced cell death. It was further shown that p38 MAPK and ERK activation was inhibited by the antioxidant, N-acetylcysteine (NAC), and that a treatment with haloperidol completely blocked the p38 and ERK activation induced by dopamine. These results suggest that dopamine induces an anti-proliferative effect and cell death via the dopamine D2 receptors, by means of the p38 MAPK and ERK pathways involving oxidative stress, in the pituitary tumor cells.
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Affiliation(s)
- Juan Ji An
- Laboratory of Molecular Biology, Medical Research Center, College of Medicine, Brain Korea 21 Project for Medical Sciences, Yonsei University, Shinchon-dong 134, Seodaemun-gu, Seoul 120-752, South Korea
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28
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Matassa AA, Kalkofen RL, Carpenter L, Biden TJ, Reyland ME. Inhibition of PKCalpha induces a PKCdelta-dependent apoptotic program in salivary epithelial cells. Cell Death Differ 2003; 10:269-77. [PMID: 12700627 DOI: 10.1038/sj.cdd.4401149] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
We have used expression of a kinase dead mutant of PKCalpha (PKCalphaKD) to explore the role of this isoform in salivary epithelial cell apoptosis. Expression of PKCalphaKD by adenovirus-mediated transduction results in a dose-dependent induction of apoptosis in salivary epithelial cells as measured by the accumulation of sub-G1 DNA, activation of caspase-3, and cleavage of PKCdelta and PKCzeta, known caspase substrates. Induction of apoptosis is accompanied by nine-fold activation of c-Jun-N-terminal kinase, and an approximately two to three-fold increase in activated mitogen-activated protein kinase (MAPK) as well as total MAPK protein. Previous studies from our laboratory have shown that PKCdelta activity is essential for the apoptotic response of salivary epithelial cells to a variety of cell toxins. To explore the contribution of PKCdelta to PKCalphaKD-induced apoptosis, salivary epithelial cells were cotransduced with PKCalphaKD and PKCdeltaKD expression vectors. Inhibition of endogenous PKCdelta blocked the ability of PKCalphaKD to induce apoptosis as indicated by cell morphology, DNA fragmentation, and caspase-3 activation, indicating that PKCdelta activity is required for the apoptotic program induced under conditions where PKCalpha is inhibited. These findings indicate that PKCalpha functions as a survival factor in salivary epithelial cells, while PKCdelta functions to regulate entry into the apoptotic pathway.
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Affiliation(s)
- A A Matassa
- Department of Craniofacial Biology, School of Dentistry, University of Colorado Health Sciences Center, Denver 80262, USA
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29
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Neve RM, Holbro T, Hynes NE. Distinct roles for phosphoinositide 3-kinase, mitogen-activated protein kinase and p38 MAPK in mediating cell cycle progression of breast cancer cells. Oncogene 2002; 21:4567-76. [PMID: 12085235 DOI: 10.1038/sj.onc.1205555] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2001] [Revised: 03/20/2002] [Accepted: 03/27/2002] [Indexed: 12/18/2022]
Abstract
Addition of the ErbB-ligand, Heregulinbeta1 (HRG), to breast tumour-derived T47D cells promotes D-cyclin expression, p21(cip1) synthesis, cyclin-dependent kinase (CDK) activation through re-distribution of p27(kip1) and DNA synthesis. In contrast EGF has no effect on T47D cell cycle progression. By comparing these two ligands and the use of specific inhibitors for phosphatidylinositol-3 kinase (PI3K), mitogen-activated protein kinase (MAPK) and p38MAPK, we have identified several molecular mechanisms required for ErbB receptor-mediated proliferation. The PI3K, MAPK and p38MAPK pathways each displayed distinct activation profiles in response to either HRG or EGF, with obvious differences in both the intensity and duration of signal output. Through inhibition of each of these pathways it is apparent that each pathway is necessary, yet insufficient alone, to stimulate proliferation. Each pathway regulates distinct subsets of essential cell cycle regulators and integration of these signal networks is required for the timely expression of these components, which culminates in cell cycle progression. Significantly, the mechanisms controlling ligand-stimulated proliferation through ErbB2 are strikingly similar to the mechanisms through which overexpressed, constitutively activated, ErbB2 orchestrates uncontrolled proliferation in cancer cells. This suggests that downstream effectors of ErbB receptors represent good therapeutic targets for breast cancer.
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Affiliation(s)
- Richard M Neve
- Department of Hematology/Oncology, UCSF San Francisco and Buck Institute, Novato, California 94945, USA.
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30
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Dumont JE, Dremier S, Pirson I, Maenhaut C. Cross signaling, cell specificity, and physiology. Am J Physiol Cell Physiol 2002; 283:C2-28. [PMID: 12055068 DOI: 10.1152/ajpcell.00581.2001] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The literature on intracellular signal transduction presents a confusing picture: every regulatory factor appears to be regulated by all signal transduction cascades and to regulate all cell processes. This contrasts with the known exquisite specificity of action of extracellular signals in different cell types in vivo. The confusion of the in vitro literature is shown to arise from several causes: the inevitable artifacts inherent in reductionism, the arguments used to establish causal effect relationships, the use of less than adequate models (cell lines, transfections, acellular systems, etc.), and the implicit assumption that networks of regulations are universal whereas they are in fact cell and stage specific. Cell specificity results from the existence in any cell type of a unique set of proteins and their isoforms at each level of signal transduction cascades, from the space structure of their components, from their combinatorial logic at each level, from the presence of modulators of signal transduction proteins and of modulators of modulators, from the time structure of extracellular signals and of their transduction, and from quantitative differences of expression of similar sets of factors.
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Affiliation(s)
- J E Dumont
- Institute of Interdisciplinary Research, Free University of Brussels, Campus Erasme, B-1070 Brussels, Belgium.
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31
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Abstract
This review focuses on the coupling specificity of the Galpha and Gbetagamma subunits of pertussis toxin (PTX)-sensitive G(i/o) proteins that mediate diverse signaling pathways, including regulation of ion channels and other effectors. Several lines of evidence indicate that specific combinations of G protein alpha, beta and gamma subunits are required for different receptors or receptor-effector networks, and that a higher degree of specificity for Galpha and Gbetagamma is observed in intact systems than reported in vitro. The structural determinants of receptor-G protein specificity remain incompletely understood, and involve receptor-G protein interaction domains, and perhaps other scaffolding processes. By identifying G protein specificity for individual receptor signaling pathways, ligands targeted to disrupt individual pathways of a given receptor could be developed.
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Affiliation(s)
- Paul R Albert
- Ottawa Health Research Institute, Neuroscience, University of Ottawa, 451 Smyth Road, K1H-8M5, Ottawa, ON, Canada.
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32
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Hannon JP, Nunn C, Stolz B, Bruns C, Weckbecker G, Lewis I, Troxler T, Hurth K, Hoyer D. Drug design at peptide receptors: somatostatin receptor ligands. J Mol Neurosci 2002; 18:15-27. [PMID: 11931345 DOI: 10.1385/jmn:18:1-2:15] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Somatostatin (SRIF, somatotropin release inhibiting factor), discovered for its inhibitory action on growth hormone (GH) secretion from pituitary, is an abundant neuropeptide. Two forms, SRIF14 and SRIF28 exist. Recently, a second family of peptides with very similar sequences and features was described; the cortistatins (CST), CST17 and CST29 which are brain selective. The five cloned SRIF receptors (sst1-5) belong to the G-protein coupled/ heptathelical receptor family. Structural and operational features distinguish two classes of receptors; SRIF1 - sst2/sst3/sst5 (high affinity for octreotide or seglitide) and SRIF2 = sst1/sst4(very low affinitty for the aforementioned ligands). The affinity of SRIF receptors for somatostatins and cortistatins is equally high, and it is not clear whether selective receptors do exist for one or the other of the peptides. Several radiologlands label all SRIF receptors, e.g., [125]LTT-SRIF28' [l25I]CGP23996, [125]Tyr10cortistatin or [125I]Tyr11SRIF14. In contrast, [125I]Tyr3octreotide, [125I]BIM23027, [125I]MK678 or [125I]D-Trp8SRIF14 label predominantly SRIF1 sites, especially sst2 and possibly sst5 receptors. In brain, [125I]Tyr3octreotide binding equates with sst2 receptor mRNA distribution. Native SRIF2receptors can be labeled with [125I]SRIF14 in the presence of high NaCl in brain (sst1) or lung (sst4) tissue. Short cyclic or linear peptide analogs show selectivity for sst2/sst5 (octreotide, lanreotide, BIM 23027), sst1 (CH-275), sst3 (sst3-ODN-8), or sst5 receptors (BIM 23268); although claims for selectivity have not always been confirmed. Beta peptides ith affinity for SRIF receptors are also reported. The general lack of SRIF receptor antagonists is unique for peptide receptors, although CYN 154806 is a selective and potent sst2 antagonist. Nonpeptide ligands are still rare, although a number of molecules have been reported with selectivity and potency for sst1 (L 757,519), sst2 (L 779,976), sst3 (L 796,778), sst4 (NNC 26-9100, L 803,087) or sst1/sst5 receptors (L 817,018). Such molecules are essential to establish the role of SRIF receptors, e.g., sst1 in hypothalamic glutamate currents: sst2 in inhibiting release of GH, glucagon, TSH, gastric acid secretion, pain, seizures and tumor growth, and sst5 in vascular remodeling and inhibition of insulin and GH release.
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33
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Lu HT, Salamon H, Horuk R. The biology and physiology of somatostatin receptors. Expert Opin Ther Targets 2001; 5:613-623. [PMID: 12540287 DOI: 10.1517/14728222.5.5.613] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The biology and therapeutic application of somatostatin and its receptors are reviewed. The focus is on recent literature and patents, especially with regard to the specific function of each somatostatin receptor subtype. Detailed mechanisms mediating the effects of somatostatin and its analogues remain to be elucidated. Nevertheless, progress is being made towards a clear picture of the cellular signalling and physiological changes regulated by somatostatin and its receptors.
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Affiliation(s)
- Hong-Tao Lu
- Berlex Biosciences, Department of Immunology, 15049 San Pablo Ave, Richmond, California 94804, USA.
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34
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Chen Z, Gibson TB, Robinson F, Silvestro L, Pearson G, Xu B, Wright A, Vanderbilt C, Cobb MH. MAP kinases. Chem Rev 2001; 101:2449-76. [PMID: 11749383 DOI: 10.1021/cr000241p] [Citation(s) in RCA: 694] [Impact Index Per Article: 30.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Z Chen
- Department of Pharmacology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas 75390, USA
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35
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Sellers LA, Simon J, Lundahl TS, Cousens DJ, Humphrey PP, Barnard EA. Adenosine nucleotides acting at the human P2Y1 receptor stimulate mitogen-activated protein kinases and induce apoptosis. J Biol Chem 2001; 276:16379-90. [PMID: 11278310 DOI: 10.1074/jbc.m006617200] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
For the widely distributed P2Y receptors for nucleotides, the transductional and functional responses downstream of their coupling to G proteins are poorly characterized. Here we describe apoptotic induction and the associated differential stimulation of mitogen-activated protein (MAP) kinase family members by the human P2Y(1) receptor. The potent P2Y(1) receptor agonist, 2-methylthio-ADP (2-MeSADP), stimulated the extracellular-signal regulated kinases (ERK1/2) (EC(50) approximately 5 nm) as well as several, but not all isoforms detected, of the stress-activated protein kinase (SAPK) family. Phospho-isoforms of p38 were unaffected. The induced kinase activity was blocked by the P2Y(1) receptor-selective antagonist, adenosine-2'-phosphate-5'-phosphate, but unaffected by pertussis toxin. In addition, the endogenous ligand ADP, and significantly also 2-MeSATP, induced concentration-dependent phosphorylation changes in the same MAP kinase family members. The sustained activation of ERK1/2 was associated with Elk-1 phosphorylation that was abolished by the MEK1 inhibitor, PD 98059. However, the concomitant transient activation of the SAPKs was not sufficient to induce c-Jun or ATF-2 phosphorylation. The transient phase of the ERK activity was partially inhibited either by the phosphatidylinositol 3-kinase inhibitor, LY 294002, or the PKC inhibitor, Gö 6976. In addition, the Src inhibitor, PP1, or expression of dominant negative Ras also attenuated the transient phase of ERK phosphorylation. In contrast, inhibition of Ras or Src had no effect on the sustained ERK activity, which was critically dependent on phosphatidylinositol 3-kinase. The transient SAPK activity was suppressed by expression of a dominant negative form of MKK4. Furthermore, this kinase-deficient mutant inhibited 2-MeSADP-induced caspase-3 stimulation and the associated decrease in cell number. In conclusion, adenosine di- and triphosphate stimulation of the human P2Y(1) receptor can transiently activate the Ras-ERK cascade via the cooperative effects of phosphatidylinositol 3-kinase, Src and PKC. The sustained ERK stimulation, via a Ras-insensitive pathway, culminates in Elk-1 activation without inducing a proliferation effect. The transient SAPK activity did not evoke transcription factor phosphorylation but was required for the P2Y(1) receptor-mediated apoptotic function.
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Affiliation(s)
- L A Sellers
- Glaxo Institute of Applied Pharmacology, Department of Pharmacology, University of Cambridge, Cambridge CB2 1QJ, United Kingdom
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Alderton F, Humphrey PP, Sellers LA. High-intensity p38 kinase activity is critical for p21(cip1) induction and the antiproliferative function of G(i) protein-coupled receptors. Mol Pharmacol 2001; 59:1119-28. [PMID: 11306695 DOI: 10.1124/mol.59.5.1119] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
G protein-coupled receptors can stimulate the p38 kinase cascade, but the effect this has on cell growth remains poorly characterized. Here we show human somatostatin sst(2) and sst(4) receptors inhibit basic fibroblast growth factor (bFGF)-induced proliferation, via a mechanism that was blocked by the p38 inhibitor PD 169316. The sst(4) receptor could also induce a proliferative activity in the absence of bFGF, which was unaffected by PD 169316. In contrast, the sst(3) receptor had no effect on basal cell growth or on the proliferation evoked by bFGF. The extracellular signal-regulated kinase activity stimulated by the sst(3) receptor was transient in duration compared with a sustained activity induced by the sst(2) and sst(4) receptors and which was critical for the proliferative response of the latter receptor. In addition, activated sst(2) and sst(4) but not sst(3) receptors evoked a prolonged phosphorylation of p38 that was amplified by bFGF. The accumulation of the cell cycle inhibitor p21(cip1) was only apparent after sst(2) and sst(4) receptor activation in the presence of bFGF, which was sensitive to PD 169316 or pertussis toxin. Thus, the contrasting antiproliferative effects evoked by the human sst(2), sst(3), and sst(4) receptors can be accounted for by their differential abilities to activate p38. This activity is critical for p21(cip1) induction, blockade of entry into S phase, as indicated by the lack of retinoblastoma protein phosphorylation, and the associated antiproliferative activity of somatostatin. Furthermore, by changing the intracellular signaling threshold of p38 through cooperative effects of somatostatin and bFGF, the sst(4) receptor can mediate opposing effects on cell proliferation.
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Affiliation(s)
- F Alderton
- Glaxo Institute of Applied Pharmacology, Department of Pharmacology, University of Cambridge, Cambridge, United Kingdom
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Abstract
Somatostatin, and the recently discovered neuropeptide cortistatin, exert their physiological actions via a family of six G protein-coupled receptors (sst1, sst2A, sst2B, sst3, sst4, sst5). Following the cloning of somatostatin receptors significant advances have been made in our understanding of their molecular, pharmacological and signaling properties although much progress remains to be done to define their physiological role in vivo. In this review, the present knowledge regarding neuroanatomical localization, signal transduction pathways, desensitization and internalization properties of somatostatin receptors is summarized. Evidence that somatostatin receptors can form homo- and heterodimers and can physically interact with members of the SSTRIP/Shank/ProSAP1/CortBP1 family is also discussed.
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Affiliation(s)
- Z Csaba
- Inserm U549, IFR Broca-Sainte Anne, Centre Paul Broca, Paris, France
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