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Börzsei R, Borbély É, Kántás B, Hudhud L, Horváth Á, Szőke É, Hetényi C, Helyes Z, Pintér E. The heptapeptide somatostatin analogue TT-232 exerts analgesic and anti-inflammatory actions via SST 4 receptor activation: In silico, in vitro and in vivo evidence in mice. Biochem Pharmacol 2023; 209:115419. [PMID: 36693436 DOI: 10.1016/j.bcp.2023.115419] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2022] [Revised: 01/16/2023] [Accepted: 01/17/2023] [Indexed: 01/22/2023]
Abstract
Since the conventional and adjuvant analgesics have limited effectiveness frequently accompanied by serious side effects, development of novel, potent pain killers for chronic neuropathic and inflammatory pain conditions is a big challenge. Somatostatin (SS) regulates endocrine, vascular, immune and neuronal functions, cell proliferation through 5 Gi protein-coupled receptors (SST1-SST5). SS released from the capsaicin-sensitive peptidergic sensory nerves mediates anti-inflammatory and antinociceptive effects without endocrine actions via SST4. The therapeutic use of the native SS is limited by its diverse biological actions and short plasma elimination half-life. Therefore, SST4 selective SS analogues could be promising analgesic and anti-inflammatory drug candidates with new mode of action. TT-232 is a cyclic heptapeptide showing great affinity to SST4 and SST1. Here, we report the in silico SST4 receptor binding mechanism, in vitro binding (competition assay) and cAMP- decreasing effect of TT-232 in SST4-expressing CHO cells, as well as its analgesic and anti-inflammatory actions in chronic neuropathic pain and arthritis models using wildtype and SST4-deficient mice. TT-232 binds to SST4 with similar interaction energy (-11.03 kcal/mol) to the superagonist J-2156, displaces somatostatin from SST4 binding (10 nM to 30 µM) and inhibits forskolin-stimulated cAMP accumulation (EC50: 371.6 ± 58.03 nmol; Emax: 78.63 ± 2.636 %). Its i.p. injection (100, 200 µg/kg) results in significant, 35.7 % and 50.4 %, analgesic effects upon single administration in chronic neuropathic pain and repeated injection in arthritis models in wildtype, but not in SST4-deficient mice. These results provide evidence that the analgesic effect of TT-232 is mediated by SST4 activation, which might open novel drug developmental potentials. Chemical compounds Chemical compounds studied in this article TT-232 (PubChem CID: 74053735).
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Affiliation(s)
- Rita Börzsei
- Department of Pharmacology and Pharmacotherapy, Medical School, University of Pécs, Szigeti str. 12, H-7624 Pécs, Hungary.
| | - Éva Borbély
- Department of Pharmacology and Pharmacotherapy, Medical School, University of Pécs, Szigeti str. 12, H-7624 Pécs, Hungary.
| | - Boglárka Kántás
- Department of Pharmacology and Pharmacotherapy, Medical School, University of Pécs, Szigeti str. 12, H-7624 Pécs, Hungary.
| | - Lina Hudhud
- Department of Pharmacology and Pharmacotherapy, Medical School, University of Pécs, Szigeti str. 12, H-7624 Pécs, Hungary.
| | - Ádám Horváth
- Department of Pharmacology and Pharmacotherapy, Medical School, University of Pécs, Szigeti str. 12, H-7624 Pécs, Hungary; Department of Pharmacology, Faculty of Pharmacy, University of Pécs, Rókus str. 2, H-7624 Pécs, Hungary.
| | - Éva Szőke
- Department of Pharmacology and Pharmacotherapy, Medical School, University of Pécs, Szigeti str. 12, H-7624 Pécs, Hungary; Algonist Biotechnologies GmbH, Karl-Farkas-Gasse str. 22, A-1030 Vienna, Austria; National Laboratory for Drug Research and Development, Magyar tudósok krt. 2, H-1117 Budapest, Hungary; Eötvös Lorand Research Network, Chronic Pain Research Group, University of Pécs, H-7624, Pécs, Hungary.
| | - Csaba Hetényi
- Department of Pharmacology and Pharmacotherapy, Medical School, University of Pécs, Szigeti str. 12, H-7624 Pécs, Hungary; Eötvös Lorand Research Network, Chronic Pain Research Group, University of Pécs, H-7624, Pécs, Hungary.
| | - Zsuzsanna Helyes
- Department of Pharmacology and Pharmacotherapy, Medical School, University of Pécs, Szigeti str. 12, H-7624 Pécs, Hungary; PharmInVivo Ltd., Szondi str. 10, H-7629 Pécs, Hungary; Algonist Biotechnologies GmbH, Karl-Farkas-Gasse str. 22, A-1030 Vienna, Austria; National Laboratory for Drug Research and Development, Magyar tudósok krt. 2, H-1117 Budapest, Hungary; Eötvös Lorand Research Network, Chronic Pain Research Group, University of Pécs, H-7624, Pécs, Hungary.
| | - Erika Pintér
- Department of Pharmacology and Pharmacotherapy, Medical School, University of Pécs, Szigeti str. 12, H-7624 Pécs, Hungary; PharmInVivo Ltd., Szondi str. 10, H-7629 Pécs, Hungary; Algonist Biotechnologies GmbH, Karl-Farkas-Gasse str. 22, A-1030 Vienna, Austria; National Laboratory for Drug Research and Development, Magyar tudósok krt. 2, H-1117 Budapest, Hungary; Eötvös Lorand Research Network, Chronic Pain Research Group, University of Pécs, H-7624, Pécs, Hungary.
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Xiong Y, Liu F, Liu D, Huang H, Wei N, Tan L, Chen J, Man H, Gong C, Lu Y, Wang J, Zhu L. Opposite effects of two estrogen receptors on tau phosphorylation through disparate effects on the miR-218/PTPA pathway. Aging Cell 2015; 14:867-77. [PMID: 26111662 PMCID: PMC4568974 DOI: 10.1111/acel.12366] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/27/2015] [Indexed: 12/14/2022] Open
Abstract
The two estrogen receptors (ERs), ERα and ERβ, mediate the diverse biological functions of estradiol. Opposite effects of ERα and ERβ have been found in estrogen-induced cancer cell proliferation and differentiation as well as in memory-related tasks. However, whether these opposite effects are implicated in the pathogenesis of Alzheimer’s disease (AD) remains unclear. Here, we find that ERα and ERβ play contrasting roles in regulating tau phosphorylation, which is a pathological hallmark of AD. ERα increases the expression of miR-218 to suppress the protein levels of its specific target, protein tyrosine phosphatase α (PTPα). The downregulation of PTPα results in the abnormal tyrosine hyperphosphorylation of glycogen synthase kinase-3β (resulting in activation) and protein phosphatase 2A (resulting in inactivation), the major tau kinase and phosphatase. Suppressing the increased expression of miR-218 inhibits the ERα-induced tau hyperphosphorylation as well as the PTPα decline. In contrast, ERβ inhibits tau phosphorylation by limiting miR-218 levels and restoring the miR-218 levels antagonized the attenuation of tau phosphorylation by ERβ. These data reveal for the first time opposing roles for ERα and ERβ in AD pathogenesis and suggest potential therapeutic targets for AD.
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Affiliation(s)
- Yan‐Si Xiong
- Department of Pathophysiology School of Basic Medicine Key Laboratory of Neurological Disorder of Education Ministry Tongji Medical College Huazhong University of Science and Technology Wuhan 430030China
- The Institute for Brain Research Collaborative Innovation Center for Brain Science Huazhong University of Science and Technology Wuhan 430030 China
| | - Fang‐Fang Liu
- Department of Pathophysiology School of Basic Medicine Key Laboratory of Neurological Disorder of Education Ministry Tongji Medical College Huazhong University of Science and Technology Wuhan 430030China
- The Institute for Brain Research Collaborative Innovation Center for Brain Science Huazhong University of Science and Technology Wuhan 430030 China
| | - Dan Liu
- The Institute for Brain Research Collaborative Innovation Center for Brain Science Huazhong University of Science and Technology Wuhan 430030 China
- Department of Genetics School of Basic Medicine Tongji Medical College Huazhong University of Science and Technology Wuhan 430030China
- Sino‐Canada Collaborative Platform on Molecular Biology of Neurological Disease Tongji Medical College Huazhong University of Science and Technology Wuhan 430030China
| | - He‐Zhou Huang
- Department of Pathophysiology School of Basic Medicine Key Laboratory of Neurological Disorder of Education Ministry Tongji Medical College Huazhong University of Science and Technology Wuhan 430030China
- The Institute for Brain Research Collaborative Innovation Center for Brain Science Huazhong University of Science and Technology Wuhan 430030 China
| | - Na Wei
- Department of Pathophysiology School of Basic Medicine Key Laboratory of Neurological Disorder of Education Ministry Tongji Medical College Huazhong University of Science and Technology Wuhan 430030China
- The Institute for Brain Research Collaborative Innovation Center for Brain Science Huazhong University of Science and Technology Wuhan 430030 China
| | - Lu Tan
- Department of Pathophysiology School of Basic Medicine Key Laboratory of Neurological Disorder of Education Ministry Tongji Medical College Huazhong University of Science and Technology Wuhan 430030China
- The Institute for Brain Research Collaborative Innovation Center for Brain Science Huazhong University of Science and Technology Wuhan 430030 China
| | - Jian‐Guo Chen
- The Institute for Brain Research Collaborative Innovation Center for Brain Science Huazhong University of Science and Technology Wuhan 430030 China
- Department of Pharmacology School of Basic Medicine Tongji Medical College Huazhong University of Science and Technology Wuhan 430030 China
| | - Heng‐Ye Man
- Department of Biology Boston University Boston MA 02215USA
| | - Cheng‐Xin Gong
- Department of Neurochemistry Inge Grundke‐Iqbal Research Floor New York State Institute for Basic Research in Developmental Disabilities Staten Island NY 10314USA
| | - Youming Lu
- The Institute for Brain Research Collaborative Innovation Center for Brain Science Huazhong University of Science and Technology Wuhan 430030 China
| | - Jian‐Zhi Wang
- Department of Pathophysiology School of Basic Medicine Key Laboratory of Neurological Disorder of Education Ministry Tongji Medical College Huazhong University of Science and Technology Wuhan 430030China
- The Institute for Brain Research Collaborative Innovation Center for Brain Science Huazhong University of Science and Technology Wuhan 430030 China
| | - Ling‐Qiang Zhu
- Department of Pathophysiology School of Basic Medicine Key Laboratory of Neurological Disorder of Education Ministry Tongji Medical College Huazhong University of Science and Technology Wuhan 430030China
- The Institute for Brain Research Collaborative Innovation Center for Brain Science Huazhong University of Science and Technology Wuhan 430030 China
- Sino‐Canada Collaborative Platform on Molecular Biology of Neurological Disease Tongji Medical College Huazhong University of Science and Technology Wuhan 430030China
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Martín-Montalvo A, González-Mariscal I, Pomares-Viciana T, Padilla-López S, Ballesteros M, Vazquez-Fonseca L, Gandolfo P, Brautigan DL, Navas P, Santos-Ocaña C. The phosphatase Ptc7 induces coenzyme Q biosynthesis by activating the hydroxylase Coq7 in yeast. J Biol Chem 2013; 288:28126-37. [PMID: 23940037 DOI: 10.1074/jbc.m113.474494] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The study of the components of mitochondrial metabolism has potential benefits for health span and lifespan because the maintenance of efficient mitochondrial function and antioxidant capacity is associated with improved health and survival. In yeast, mitochondrial function requires the tight control of several metabolic processes such as coenzyme Q biosynthesis, assuring an appropriate energy supply and antioxidant functions. Many mitochondrial processes are regulated by phosphorylation cycles mediated by protein kinases and phosphatases. In this study, we determined that the mitochondrial phosphatase Ptc7p, a Ser/Thr phosphatase, was required to regulate coenzyme Q6 biosynthesis, which in turn activated aerobic metabolism and enhanced oxidative stress resistance. We showed that Ptc7p phosphatase specifically activated coenzyme Q6 biosynthesis through the dephosphorylation of the demethoxy-Q6 hydroxylase Coq7p. The current findings revealed that Ptc7p is a regulator of mitochondrial metabolism that is essential to maintain proper function of the mitochondria by regulating energy metabolism and oxidative stress resistance.
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Affiliation(s)
- Alejandro Martín-Montalvo
- From the Centro Andaluz de Biología del Desarrollo, Universidad Pablo de Olavide-Consejo Superior de Investigaciones Científicas (CSIC), Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER) Instituto de Salud Carlos III, Sevilla 41013, Spain
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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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Wang J, Yu L, Zheng X. PTPα-mediated Src activation by EGF in human breast cancer cells. Acta Biochim Biophys Sin (Shanghai) 2013; 45:320-9. [PMID: 23532252 DOI: 10.1093/abbs/gmt005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Protein tyrosine phosphatase alpha (PTPα) functions as an activator of Src by dephosphorylating Tyr527/530, a critical negative regulatory site. The increase of PTPα catalytic activity requires its phosphorylation at Ser180 and/or Ser204 and its dissociation from PTPα/Grb2 complex. Here, we show that epidermal growth factor (EGF) stimulation increases the ability of PTPα to activate Src by dephosphorylating Tyr530 in BT-20 and SKBR3 breast cancer cell lines. Treatment of these cells with EGF transiently decreased the association of PTPα with Grb2 and enhanced PTPα catalytic activity via Ser180 and Ser204 phosphorylation that was blocked by the protein kinase C delta (PKCδ) inhibitor rottlerin or knockdown of PKCδ by siRNA or by the overexpression of PTPαS180A/S204A mutant. PTPα siRNA blocked EGF-mediated Src activation in cancer cells and inhibited on colony formation, whereas control siRNA did not. These results suggested that PTPα links activation of epidermal growth factor receptor (EGFR) signaling with Src activation and may provide a novel therapeutic target for treatment of breast cancer.
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Affiliation(s)
- Jiamin Wang
- Department of Biochemistry and Molecular Cell Biology, Shanghai JiaoTong University School of Medicine, Shanghai 200025, China
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Buitrago C, Costabel M, Boland R. PKC and PTPα participate in Src activation by 1α,25OH2 vitamin D3 in C2C12 skeletal muscle cells. Mol Cell Endocrinol 2011; 339:81-9. [PMID: 21459125 DOI: 10.1016/j.mce.2011.03.022] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/15/2010] [Revised: 02/22/2011] [Accepted: 03/25/2011] [Indexed: 01/15/2023]
Abstract
We previously demonstrated that 1α,25(OH)(2)-vitamin D(3) [1α,25(OH)(2)D(3)] induces Src activation, which mediates the hormone-dependent ERK1/2 and p38 MAPK phosphorylation in skeletal muscle cells. In the present study, we have investigated upstream steps whereby 1α,25(OH)(2)D(3) may act to transmit its signal to Src. Preincubation with the PKC inhibitor Ro318220 demonstrated the participation of PKC in 1α,25(OH)(2)D(3)-dependent Src activation. Of interest, the hormone promoted the activation of δ the isoform of PKC. We also explored the role of PTPα in PKC-mediated Src stimulation. Silencing of PTPα with a specific siRNA suppressed Src activation induced by 1α,25(OH)(2)D(3). Hormone treatment increased PTPα (Tyr789) phosphorylation and PKC-dependent phosphatase activity. Accordingly, 1α,25(OH)(2)D(3) promoted serine phosphorylation of PTPα in a PKC-dependent manner. Confocal immunocytochemistry and co-immunoprecipitation assays revealed that the hormone induces the co-localization of Src and PTPα with PKC participation. Computational analysis revealed that the electrostatic interaction between Src and PTPα is favored when PTPα is phosphorylated in Tyr789. These data suggest that 1α,25(OH)(2)D(3) acts in skeletal muscle upstream on MAPK cascades sequentially activating PKC, PTPα and Src.
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Affiliation(s)
- Claudia Buitrago
- Departamento de Biología, Bioquímica & Farmacia, Universidad Nacional del Sur., San Juan 670, Bahía Blanca 8000, Argentina.
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Ye H, Zhao T, Tan YLJ, Liu J, Pallen CJ, Xiao ZC. Receptor-like protein-tyrosine phosphatase α enhances cell surface expression of neural adhesion molecule NB-3. J Biol Chem 2011; 286:26071-80. [PMID: 21622556 DOI: 10.1074/jbc.m110.214080] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Neural adhesion molecule NB-3 plays an important role in the apical dendrite development of layer V pyramidal neurons in the visual cortex, and receptor-like protein-tyrosine phosphatase α (PTPα) mediates NB-3 signaling in this process. Here we investigated the role of PTPα in regulating cell surface expression of NB-3. We found that cortical neurons from PTPα knock-out mice exhibited a lower level of NB-3 at the cell surface. When expressed in COS1 cells, NB-3 was enriched in the Golgi apparatus with a low level of cell surface expression. However, co-expression of PTPα increased the cell surface distribution of NB-3. Further analysis showed that PTPα facilitated Golgi exit of NB-3 and stabilized NB-3 protein at the cell surface by preventing its release from the plasma membrane. The extracellular region of PTPα but not its catalytic activity is necessary for its effect on NB-3 expression. Thus, the PTPα-mediated increase of NB-3 level at the cell surface represents a novel function of PTPα in NB-3 signaling in neural development.
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Affiliation(s)
- Haihong Ye
- State Key Laboratory of Brain and Cognitive Sciences, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
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Bodrikov V, Sytnyk V, Leshchyns'ka I, den Hertog J, Schachner M. NCAM induces CaMKIIalpha-mediated RPTPalpha phosphorylation to enhance its catalytic activity and neurite outgrowth. ACTA ACUST UNITED AC 2008; 182:1185-200. [PMID: 18809727 PMCID: PMC2542478 DOI: 10.1083/jcb.200803045] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Receptor protein tyrosine phosphatase α (RPTPα) phosphatase activity is required for intracellular signaling cascades that are activated in motile cells and growing neurites. Little is known, however, about mechanisms that coordinate RPTPα activity with cell behavior. We show that clustering of neural cell adhesion molecule (NCAM) at the cell surface is coupled to an increase in serine phosphorylation and phosphatase activity of RPTPα. NCAM associates with T- and L-type voltage-dependent Ca2+ channels, and NCAM clustering at the cell surface results in Ca2+ influx via these channels and activation of NCAM-associated calmodulin-dependent protein kinase IIα (CaMKIIα). Clustering of NCAM promotes its redistribution to lipid rafts and the formation of a NCAM–RPTPα–CaMKIIα complex, resulting in serine phosphorylation of RPTPα by CaMKIIα. Overexpression of RPTPα with mutated Ser180 and Ser204 interferes with NCAM-induced neurite outgrowth, which indicates that neurite extension depends on NCAM-induced up-regulation of RPTPα activity. Thus, we reveal a novel function for a cell adhesion molecule in coordination of cell behavior with intracellular phosphatase activity.
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Affiliation(s)
- Vsevolod Bodrikov
- Zentrum für Molekulare Neurobiologie, Universität Hamburg, 20246 Hamburg, Germany
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Szokolóczi O, Schwab R, Peták I, Orfi L, Pap A, Eberle AN, Szüts T, Kéril G. TT232, A Novel Signal Transduction Inhibitory Compound in the Therapy of Cancer and Inflammatory Diseases. J Recept Signal Transduct Res 2008; 25:217-35. [PMID: 16393913 DOI: 10.1080/10799890500464621] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
TT-232 is a structural analogue of somatostatin exhibiting strong and selective growth-inhibitory effects, inhibition of neurogenic inflammation, as well as general anti-inflammatory and analgesic potential without the wide-ranging endocrine side effects of the parent hormone and its "traditional" analogues. The anti-inflammatory action of TT-232 is mediated through the SSTR4 receptor, and its antitumor activity is mediated through the SSTR1 receptor and by the tumor-specific isoform of pyruvate kinase. Its mechanism of action is in line with a new era of molecular medicine called signal transduction therapy, where "false" intracellular or intercellular communication is inhibited or corrected without interfering with basic cell functions and machinery. TT232 has passed phase I clinical trials without toxicity and significant side effects, and phase II studies are running for oncological and anti-inflammatory indications, respectively. This compound has the perspective to become the first drug in molecularly targeted therapy of inflammation where a combined effect of anti-inflammatory, analgesic, and neurogenic inflammation-inhibiting activity can be achieved.
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Affiliation(s)
- Orsolya Szokolóczi
- Rational Drug Design Laboratories, Cooperative Research Center, Semmelweis University, Budapest, Hungary
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Simon Á, Kéri G, Kardos J. Comparison of the binding modes of TT-232 in somatostatin receptors type 1 and 4. ACTA ACUST UNITED AC 2007. [DOI: 10.1016/j.theochem.2007.04.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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Cervia D, Bagnoli P. An update on somatostatin receptor signaling in native systems and new insights on their pathophysiology. Pharmacol Ther 2007; 116:322-41. [PMID: 17719647 DOI: 10.1016/j.pharmthera.2007.06.010] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2007] [Accepted: 06/28/2007] [Indexed: 12/20/2022]
Abstract
The peptide somatostatin (SRIF) has important physiological effects, mostly inhibitory, which have formed the basis for the clinical use of SRIF compounds. SRIF binding to its 5 guanine nucleotide-binding proteins-coupled receptors leads to the modulation of multiple transduction pathways. However, our current understanding of signaling exerted by receptors endogenously expressed in different cells/tissues reflects a rather complicated picture. On the other hand, the complexity of SRIF receptor signaling in pathologies, including pituitary and nervous system diseases, may be studied not only as alternative intervention points for the modulation of SRIF function but also to exploit new chemical space for drug-like molecules.
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Affiliation(s)
- Davide Cervia
- Department of Environmental Sciences, University of Tuscia, largo dell'Università snc, blocco D, 01100 Viterbo, Italy.
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Steták A, Veress R, Ovádi J, Csermely P, Kéri G, Ullrich A. Nuclear translocation of the tumor marker pyruvate kinase M2 induces programmed cell death. Cancer Res 2007; 67:1602-8. [PMID: 17308100 DOI: 10.1158/0008-5472.can-06-2870] [Citation(s) in RCA: 144] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Cancer cells often fail to respond to stimuli that normally activate their intrinsic apoptotic machinery. Moreover, they are able to adapt to hypoxia by changing their glycolytic rate. Pyruvate kinase (PK) is a rate-limiting enzyme in glycolysis that is converted to a less active dimer form of PKM2 isoenzyme during oncogenesis. Here, we show that both somatostatin and the structural analogue TT-232 interact with the PKM subtype. We further show that the PKM2 is translocated to the nucleus in response to TT-232 and different apoptotic agents. Nuclear translocation of PKM2 is sufficient to induce cell death that is caspase independent, isoform specific, and independent of its enzymatic activity. These results show that the tumor marker PKM2 plays a general role in caspase-independent cell death of tumor cells and thereby defines this glycolytic enzyme as a novel target for cancer therapy development.
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Affiliation(s)
- Attila Steták
- Department of Molecular Biology, Max-Planck-Institute for Biochemistry, Martinsried, Germany.
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Theodoropoulou M, Zhang J, Laupheimer S, Paez-Pereda M, Erneux C, Florio T, Pagotto U, Stalla GK. Octreotide, a Somatostatin Analogue, Mediates Its Antiproliferative Action in Pituitary Tumor Cells by Altering Phosphatidylinositol 3-Kinase Signaling and Inducing Zac1 Expression. Cancer Res 2006; 66:1576-82. [PMID: 16452215 DOI: 10.1158/0008-5472.can-05-1189] [Citation(s) in RCA: 148] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Somatostatin limits cell growth by inhibiting the proliferative activity of growth factor receptors. In this study, it is shown that in pituitary tumor cells, the somatostatin analogue octreotide produces its antiproliferative action by inducing the expression the tumor suppressor gene Zac1. ZAC/Zac1 induces cell cycle arrest and apoptosis and is highly expressed in normal pituitary, mammary, and ovarian glands but is down-regulated in pituitary, breast, and ovarian tumors. Knocking down Zac1 by RNA interference abolished the antiproliferative effect of octreotide in pituitary tumor cells, indicating that Zac1 is necessary for the action of octreotide. The effect of octreotide on Zac1 expression was pertussis toxin sensitive and was abolished after transfection with a dominant negative vector for SHP-1. Zac1 is a target of the phosphatidylinositol 3-kinase (PI3K) survival pathway. Octreotide treatment decreased the tyrosine phosphorylation levels of the PI3K regulatory subunit p85, induced dephosphorylation of phosphoinositide-dependent kinase 1 (PDK1) and Akt, and activated glycogen synthase kinase 3beta (GSKbeta). Therefore, in pituitary tumor cells, somatostatin analogues produce their antiproliferative action by acting on the PI3K/Akt signaling pathway and increasing Zac1 gene expression.
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Affiliation(s)
- Marily Theodoropoulou
- Department of Endocrinology, Max Planck Institute of Psychiatry, Kraepelinstrasse 10, D-80804 Munich, Germany.
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Vary TC, Goodman S, Kilpatrick LE, Lynch CJ. Nutrient regulation of PKCepsilon is mediated by leucine, not insulin, in skeletal muscle. Am J Physiol Endocrinol Metab 2005; 289:E684-94. [PMID: 15886222 DOI: 10.1152/ajpendo.00613.2004] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Nutrients enhance signaling pathways involved in skeletal muscle growth through an increased rate of protein synthesis. These studies have led to an understanding of the potential role of the mammalian target of rapamycin (mTOR) in this process. However, activation of mTOR cannot account for all the stimulatory effects of nutrients. The purpose of these experiments was to examine the effect of nutrients on the cellular distribution and activation state of novel PKC isoforms (PKCepsilon and PKCdelta) in the gastrocnemius of rats by use of modification state-dependent phosphopeptide-specific antibodies. The phosphorylation of PKCepsilon on the catalytic domain autophosphorylation site (Ser(729)) was elevated during feeding and then returned to basal levels when the feeding period ended. Meal feeding augmented the phosphorylation of the downstream effectors of mTOR, namely S6K1 and 4E-BP1. In contrast, the phosphorylation of PKCdelta on either the catalytic domain autophosphorylation site (Ser(643)) or activation loop site (Thr(505)) was unaffected. Similar results were obtained when animals were given leucine either acutely via gavage or chronically by dietary supplementations. The effect of leucine was not mimicked by injecting animals with insulin but could be induced by gavage with norleucine, a structural analog of leucine that does not increase plasma insulin concentration. Thus rises in insulin secondary to meal intake or leucine gavage are probably not responsible for increased phosphorylation of PKCepsilon in response to meal feeding. Elevating the leucine concentration stimulated the phosphorylation of PKCepsilon in gastrocnemius from perfused hindlimb and caused a shift in the distribution of PKCepsilon from the membrane fraction to the cytosolic fraction. The results indicate that leucine leads to an activation (autophosphorylation) and subcellular redistribution of PKCepsilon, but not PKCdelta, in gastrocnemius both in vivo and in vitro. Furthermore, activation of the mTOR signaling pathway above basal conditions does not appear to be necessary to induce phosphorylation or translocation of PKCepsilon, suggesting that multiple signaling pathways become activated with leucine.
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Affiliation(s)
- Thomas C Vary
- Dept. of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey, PA 17033, USA.
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15
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Ginnan R, Singer HA. PKC-δ-dependent pathways contribute to PDGF-stimulated ERK1/2 activation in vascular smooth muscle. Am J Physiol Cell Physiol 2005; 288:C1193-201. [PMID: 15677375 DOI: 10.1152/ajpcell.00499.2004] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Platelet-derived growth factor (PDGF) is an important regulator of vascular smooth muscle (VSM) cell growth and migration and has been identified as a key mediator of neointima formation resulting from vascular injury. PDGF exerts its effects, in part, through activation of ERK1/2. Previously, we reported that PKC-δ, specifically compared with PKC-α, mediated phorbol ester- and ATP-dependent activation of ERK1/2 in VSM cells. The purpose of this study was to determine whether PKC-δ was involved in PDGF-dependent activation of ERK1/2 in VSM cells. The addition of PDGF resulted in the activation, and Src family kinase-dependent tyrosine phosphorylation, of PKC-δ. Treatment with rottlerin (0.1–10 μM), a selective PKC-δ inhibitor, or adenoviral overexpression of kinase-negative PKC-δ significantly attenuated PDGF-induced activation of ERK1/2. The effects of the PKC-δ inhibitors decreased with increasing concentrations of activator PDGF. Interestingly, treatment with Gö6976 (0.1–3 μM), a selective inhibitor of cPKCs, or adenoviral overexpression of kinase-negative PKC-α also inhibited PDGF-stimulated ERK1/2. Furthermore, inhibition of cPKC activity with Gö6976 or overexpression of kinase-negative PKC-α attenuated PKC-δ activation and tyrosine phosphorylation in response to PDGF. These studies indicate involvement of both PKC-δ and PKC-α isozymes in PDGF-stimulated signaling in VSM and suggest an unexpected role for PKC-α in the regulation of PKC-δ activity.
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Affiliation(s)
- Roman Ginnan
- Center for Cardiovascular Sciences, Albany Medical College (MC8) 47 New Scotland Ave., Albany, NY 12208, USA.
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16
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Ensslen SE, Brady-Kalnay SM. PTPmu signaling via PKCdelta is instructive for retinal ganglion cell guidance. Mol Cell Neurosci 2004; 25:558-71. [PMID: 15080886 DOI: 10.1016/j.mcn.2003.12.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2003] [Revised: 11/24/2003] [Accepted: 12/03/2003] [Indexed: 01/03/2023] Open
Abstract
The receptor protein tyrosine phosphatase (RPTP) PTPmu mediates distinct cellular responses in nasal and temporal retinal ganglion cell (RGC) axons. PTPmu is permissive for nasal RGC neurite outgrowth and inhibitory to temporal RGCs. In addition, PTPmu causes preferential temporal growth cone collapse. Previous studies demonstrated that PTPmu associates with the scaffolding protein RACK1 and the protein kinase C-delta (PKCdelta) isoform in chick retina and that PKCdelta activity is required for PTPmu-mediated RGC outgrowth. Using in vitro stripe and collapse assays, we find that PKCdelta activity is required for both inhibitory and permissive responses of RGCs to PTPmu, with higher levels of PKCdelta activation associated with temporal growth cone collapse and repulsion. A potential mechanism for differential PKCdelta activation is due to the gradient of PTPmu expression in the retina. PTPmu is expressed in a high temporal, low nasal step gradient in the retina. In support of this, overexpression of exogenous PTPmu in nasal neurites results in a phenotypic switch from permissive to repulsive in response to PTPmu. Together, these results suggest that the differential expression of PTPmu within the retina is instructive for RGC guidance and that the magnitude of PKCdelta activation in response to PTPmu signaling results in the distinct cellular behaviors of nasal and temporal RGCs.
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Affiliation(s)
- Sonya E Ensslen
- Department of Neurosciences, School of Medicine, Case Western Reserve University, Cleveland, OH 44106-4960, USA
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17
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Simon A, Czajlik A, Perczel A, Kéri G, Nyikos L, Emri Z, Kardos J. Binding crevice for TT-232 in a homology model of type 1 somatostatin receptor. Biochem Biophys Res Commun 2004; 316:1059-64. [PMID: 15044092 DOI: 10.1016/j.bbrc.2004.02.161] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2004] [Indexed: 11/30/2022]
Abstract
Somatostatin receptor type 1 was modelled based on the atomic structure of bovine rhodopsin. Possible ways of binding interaction between somatostatin receptor type 1 and TT-232, a cycloheptapeptide analogue of somatostatin with broad therapeutic potential, were analysed by molecular docking. The twelve TT-232 conformations, obtained by NMR measurements in H(2)O-D(2)O mixture, were similar, disclosing a consensus backbone conformation. Several residues interacting with TT-232, such as Val133, Asp137 (helix 3), Arg197 (helix 4), Phe287, Gln291, Asn294 (helix 6), Ser305, and Tyr313 (helix 7), were found. In accordance, in vitro binding experiments indicated high-affinity binding of TT-232 to (125)I labelled somatostatin sites in brain membranes. The single binding crevice obtained by docking may allow the design and discovery of new peptidomimetics of TT-232 in the future.
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Affiliation(s)
- Agnes Simon
- Department of Neurochemistry, Chemical Research Center, Hungarian Academy of Sciences, Pusztaszeri út 59-67, Budapest H-1025, Hungary.
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18
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Abstract
TT-232 (D-Phe-Cys-Tyr-D-Trp-Lys-Cys-Thr-NH2) has been developed as an antitumor somatostatin analog. TT-232 has no growth hormone release inhibitory effect and does not inhibit the secretion of gastric acid. This analog induces apoptosis in and exerts pronounced antiproliferative effects on various human tumors (colon, pancreas, lymphoma, leukemia, melanoma, hepatoma) cell lines. The growth of human xenografts (prostate, breast carcinoma, lymphoma, melanoma) and animal tumors (colon-26, P-388, S-180, B16, MXT) was inhibited by TT-232 (dose range: 30-750 microg/kg/day) in 54-98% of cases. Continuous long-term infusion proved to be the most effective way of administration. TT-232 combined with decarbazine or etoposide treatment enhanced the antitumor activity of these drugs on human melanoma and lymphoma xenografts, respectively. Regarding the mode of action, TT-232 activates cell cycle inhibitors via SSTR receptors, inhibits tyrosine kinases through interfering with the proliferative signaling cascades, and interacts with an intracellular receptor and an enzyme involved in glycolysis causing translocation of this enzyme to the nucleus, thus inducing apoptosis. TT-232 may be a promising candidate in the therapy of human malignancies.
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Affiliation(s)
- B Szende
- First Department of Pathology and Experimental Cancer Research, Semmelweis University, Molecular Pathology Research Group Joint Research Organisation of the Hungarian Academy of Sciences and Semmelweis University, Budapest, Hungary.
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19
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Kanthasamy AG, Kitazawa M, Kanthasamy A, Anantharam V. Role of proteolytic activation of protein kinase Cdelta in oxidative stress-induced apoptosis. Antioxid Redox Signal 2003; 5:609-20. [PMID: 14580317 DOI: 10.1089/152308603770310275] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Protein kinase Cdelta (PKCdelta), a member of the novel PKC family, is emerging as a redox-sensitive kinase in various cell types. Oxidative stress activates the PKCdelta kinase by translocation, tyrosine phosphorylation, or proteolysis. During proteolysis, caspase-3 cleaves the native PKCdelta (72-74 kDa) into 41-kDa catalytically active and 38-kDa regulatory fragments to persistently activate the kinase. The proteolytic activation of PKCdelta plays a key role in promoting apoptotic cell death in various cell types, including neuronal cells. Attenuation of PKCdelta proteolytic activation by antioxidants suggests that the cellular redox status can influence activation of the proapoptotic kinase. PKCdelta may also amplify apoptotic signaling via positive feedback activation of the caspase cascade. Thus, the dual role of PKCdelta as a mediator and amplifier of apoptosis may be important in the pathogenesis of major neurodegenerative disorders, such as Parkinson's disease, Alzheimer's disease, and Huntington disease.
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Affiliation(s)
- Anumantha G Kanthasamy
- Parkinson's Disorders Research Program, Department of Biomedical Sciences, Iowa State University, Ames, IA 50011, USA.
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20
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Brandt DT, Goerke A, Heuer M, Gimona M, Leitges M, Kremmer E, Lammers R, Haller H, Mischak H. Protein kinase C delta induces Src kinase activity via activation of the protein tyrosine phosphatase PTP alpha. J Biol Chem 2003; 278:34073-8. [PMID: 12826681 DOI: 10.1074/jbc.m211650200] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Previously we have shown that protein kinase C (PKC)-mediated reorganization of the actin cytoskeleton in smooth muscle cells is transmitted by the non-receptor tyrosine kinase, Src. Several authors have described how 12-O-tetradecanoylphorbol-13-acetate (TPA) stimulation of cells results in an increase of Src activity, but the mechanism of the PKC-mediated Src activation is unknown. Using PKC isozymes purified from Spodoptera frugiperda insect cells, we show here that PKC is not able to activate Src directly. Our data reveal that the PKC-dependent Src activation occurs via the activation of the protein tyrosine phosphatase (PTP) PTP alpha. PTP alpha becomes activated in vivo after TPA stimulation. Further, we show that PKC delta phosphorylates and activates only PTP alpha in vitro but not any other of the TPA-responsive PKC isozymes that are expressed in A7r5 rat aortic smooth muscle cells. To further substantiate our data, we show that cells lacking PKC delta have a markedly reduced PTP alpha and Src activity after 12-O-tetradecanoylphorbol-13-acetate stimulation. These data support a model in which the main mechanism of 12-O-tetradecanoylphorbol-13-acetate-induced Src activation is the direct phosphorylation and activation of PTP alpha by PKC delta, which in turn dephosphorylates and activates Src.
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Affiliation(s)
- Dominique T Brandt
- Medizinische Hochschule Hannover, Department of Nephrology, 30625 Hannover, Germany
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21
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Szende B, Horváth A, Bökönyi G, Kéri G. Effect of a novel somatostatin analogue combined with cytotoxic drugs on human tumour xenografts and metastasis of B16 melanoma. Br J Cancer 2003; 88:132-6. [PMID: 12556972 PMCID: PMC2376778 DOI: 10.1038/sj.bjc.6600668] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
A novel somatostatin analogue, TT-232 (which inhibits the proliferation of various cell cultures and transplantable mouse tumours), was examined regarding its effect on human melanoma and lymphoma xenografts as a single treatment or in combination with DTIC (dacarbazine) and etoposide. TT-232 inhibited the growth of HT-18 melanoma xenografts, a dose of 5 mg kg(-1) being the most effective. Combination of 1 mg kg(-1) TT-232 with 30 or 60 mg kg(-1) DTIC (administered daily) resulted in a stronger inhibitory effect compared to TT-232 or DTIC as a single modality. Antimetastatic effect of TT-232 treatment combined with DTIC was studied using the B16 mouse melanoma muscle - lung metastasis model. The number of lung metastases of B16 melanoma could be decreased by the daily administration of 1 mg kg(-1) TT-232 or 60 mg kg(-1), but not of 30 mg kg(-1) DTIC. TT-232, combined with 30 or 60 mg kg(-1) DTIC decreased the lung metastasis number significantly lower than the control. Nearly 50% growth inhibition of HT-58 lymphoma was achieved by daily treatment with 1 mg kg(-1) TT-232. 5 mg kg(-1) etoposide, administered daily, resulted in a similar effect. The combination of 1 mg kg(-1) TT-232 and 5 mg kg(-1) etoposide was significantly more effective than TT-232 or etoposide as a single treatment. The very strong tumour growth inhibitory effect of 10 mg kg(-1) etoposide could even be increased by combination with TT-232. These experimental data suggest that TT-232 may be an effective new tool in the combination chemotherapy of malignant tumours like melanoma and lymphoma.
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Affiliation(s)
- B Szende
- 1st Department of Pathology and Experimental Cancer Research, Semmelweis University and Molecular Pathology Research Group Joint Research Organisation of the Hungarian Academy of Sciences, and Semmelweis University Budapest, Hungary.
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22
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Buchan AMJ, Lin CY, Choi J, Barber DL. Somatostatin, acting at receptor subtype 1, inhibits Rho activity, the assembly of actin stress fibers, and cell migration. J Biol Chem 2002; 277:28431-8. [PMID: 12045195 DOI: 10.1074/jbc.m201261200] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Somatostatin regulates multiple biological functions by acting through a family of five G protein-coupled receptors, somatostatin receptors (SSTRs) 1-5. Although all five receptor subtypes inhibit adenylate cyclase activity and decrease intracellular cAMP levels, specific receptor subtypes also couple to additional signaling pathways. In CCL39 fibroblasts expressing either human SSTR1 or SSTR2, we demonstrate that activation of SSTR1 (but not SSTR2) attenuated both thrombin- and integrin-stimulated Rho-GTP complex formation. The reduction in Rho-GTP formation in the presence of somatostatin was associated with decreased translocation of Rho and LIM kinase to the plasma membrane and fewer focal contacts. Activation of Rho resulted in the formation of intracellular actin stress fibers and cell migration. In CCL39-R1 cells, somatostatin treatment prevented actin stress fiber assembly and attenuated thrombin-stimulated cell migration through Transwell membranes to basal levels. To show that native SSTR1 shares the ability to inhibit Rho activation, we demonstrated that somatostatin treatment of human umbilical vein endothelial cells attenuated thrombin-stimulated Rho-GTP accumulation. These data show for the first time that a G protein-coupled receptor, SSTR1, inhibits the activation of Rho, the assembly of focal adhesions and actin stress fibers, and cell migration.
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Affiliation(s)
- Alison M J Buchan
- Department of Physiology, University of British Columbia, Vancouver V6T 1Z3, Canada.
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23
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Kilpatrick LE, Lee JY, Haines KM, Campbell DE, Sullivan KE, Korchak HM. A role for PKC-delta and PI 3-kinase in TNF-alpha-mediated antiapoptotic signaling in the human neutrophil. Am J Physiol Cell Physiol 2002; 283:C48-57. [PMID: 12055072 DOI: 10.1152/ajpcell.00385.2001] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The proinflammatory cytokine tumor necrosis factor (TNF)-alpha has been implicated in the attenuation of neutrophil spontaneous apoptosis during sepsis. Antiapoptotic signaling is principally mediated through the p60TNF receptor (p60TNFR). In neutrophils, TNF-alpha is an incomplete secretagogue and requires input from a ligated integrin(s) for neutrophil activation. In adherent neutrophils, TNF-alpha triggers association of both protein kinase C (PKC)-delta and phosphatidylinositol (PI) 3-kinase with the p60TNFR. In this study, a role for PKC-delta and PI 3-kinase in TNF-alpha-mediated antiapoptotic signaling was examined. TNF-alpha inhibited spontaneous apoptosis in fibronectin-adherent neutrophils, and this antiapoptotic signaling was blocked by the PKC-delta inhibitor rottlerin, but not by an inhibitor of Ca(2+)-dependent PKC isotypes, Go-6976. Inhibition of PI 3-kinase by LY-294002 also inhibited TNF-alpha-mediated antiapoptotic signaling. Cycloheximide blocked TNF-alpha-mediated antiapoptotic signaling, suggesting protein synthesis is required. Inhibition of either PKC-delta or PI 3-kinase attenuated TNF-alpha-mediated activation of the antiapoptotic transcription factor NFkappaB. Thus both PKC-delta and PI 3-kinase have essential roles in TNF-alpha-mediated antiapoptotic signaling in adherent neutrophils.
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Affiliation(s)
- Laurie E Kilpatrick
- Department of Pediatrics, University of Pennsylvania School of Medicine and the Joseph Stokes Jr. Research Institute, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania 19104, USA.
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24
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Zheng XM, Resnick RJ, Shalloway D. Mitotic activation of protein-tyrosine phosphatase alpha and regulation of its Src-mediated transforming activity by its sites of protein kinase C phosphorylation. J Biol Chem 2002; 277:21922-9. [PMID: 11923305 PMCID: PMC5641391 DOI: 10.1074/jbc.m201394200] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
During mitosis, the catalytic activity of protein-tyrosine phosphatase (PTP) alpha is enhanced, and its inhibitory binding to Grb2, which specifically blocks Src dephosphorylation, is decreased. These effects act synergistically to activate Src in mitosis. We show here that these effects are abrogated by mutation of Ser180 and/or Ser204, the sites of protein kinase C-mediated phosphorylation within PTPalpha. Moreover, either a Ser-to-Ala substitution or serine dephosphorylation specifically eliminated the ability of PTPalpha to dephosphorylate and activate Src even during interphase. This explains why the substitutions eliminated PTPalpha transforming activity, even though PTPalpha interphase dephosphorylation of nonspecific substrates was only slightly decreased. This occurred without change in the phosphorylation of PTPalpha at Tyr789, which is required for "phosphotyrosine displacement" during Src dephosphorylation. Thus, in addition to increasing PTPalpha nonspecific catalytic activity, Ser180 and Ser204 phosphorylation (along with Tyr789 phosphorylation) regulates PTPalpha substrate specificity. This involves serine phosphorylation-dependent differential modulation of the affinity of Tyr(P)789 for the Src and Grb2 SH2 domains. The results suggest that protein kinase C may participate in the mitotic activation of PTPalpha and Src and that there are intramolecular interactions between the PTPalpha C-terminal and membrane-proximal regions that are regulated, at least in part, by serine phosphorylation.
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Affiliation(s)
- Xin-Min Zheng
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853
| | - Ross J. Resnick
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853
| | - David Shalloway
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853
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