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Lu J, Piper SJ, Zhao P, Miller LJ, Wootten D, Sexton PM. Targeting VIP and PACAP Receptor Signaling: New Insights into Designing Drugs for the PACAP Subfamily of Receptors. Int J Mol Sci 2022; 23:8069. [PMID: 35897648 PMCID: PMC9331257 DOI: 10.3390/ijms23158069] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Revised: 07/18/2022] [Accepted: 07/20/2022] [Indexed: 12/16/2022] Open
Abstract
Pituitary Adenylate Cyclase-Activating Peptide (PACAP) and Vasoactive Intestinal Peptide (VIP) are neuropeptides involved in a diverse array of physiological and pathological processes through activating the PACAP subfamily of class B1 G protein-coupled receptors (GPCRs): VIP receptor 1 (VPAC1R), VIP receptor 2 (VPAC2R), and PACAP type I receptor (PAC1R). VIP and PACAP share nearly 70% amino acid sequence identity, while their receptors PAC1R, VPAC1R, and VPAC2R share 60% homology in the transmembrane regions of the receptor. PACAP binds with high affinity to all three receptors, while VIP binds with high affinity to VPAC1R and VPAC2R, and has a thousand-fold lower affinity for PAC1R compared to PACAP. Due to the wide distribution of VIP and PACAP receptors in the body, potential therapeutic applications of drugs targeting these receptors, as well as expected undesired side effects, are numerous. Designing selective therapeutics targeting these receptors remains challenging due to their structural similarities. This review discusses recent discoveries on the molecular mechanisms involved in the selectivity and signaling of the PACAP subfamily of receptors, and future considerations for therapeutic targeting.
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Affiliation(s)
- Jessica Lu
- Drug Discovery Biology, Australian Research Council Centre for Cryo-Electron Microscopy of Membrane Proteins, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052, Australia
| | - Sarah J Piper
- Drug Discovery Biology, Australian Research Council Centre for Cryo-Electron Microscopy of Membrane Proteins, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052, Australia
| | - Peishen Zhao
- Drug Discovery Biology, Australian Research Council Centre for Cryo-Electron Microscopy of Membrane Proteins, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052, Australia
| | - Laurence J Miller
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Scottsdale, AZ 85259, USA
| | - Denise Wootten
- Drug Discovery Biology, Australian Research Council Centre for Cryo-Electron Microscopy of Membrane Proteins, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052, Australia
| | - Patrick M Sexton
- Drug Discovery Biology, Australian Research Council Centre for Cryo-Electron Microscopy of Membrane Proteins, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052, Australia
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Li W, Trigg JS, Taghert PH. Regulation of PDF receptor signaling controlling daily locomotor rhythms in Drosophila. PLoS Genet 2022; 18:e1010013. [PMID: 35605015 PMCID: PMC9166358 DOI: 10.1371/journal.pgen.1010013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2022] [Revised: 06/03/2022] [Accepted: 04/27/2022] [Indexed: 11/19/2022] Open
Abstract
Each day and in conjunction with ambient daylight conditions, neuropeptide PDF regulates the phase and amplitude of locomotor activity rhythms in Drosophila through its receptor, PDFR, a Family B G protein-coupled receptor (GPCR). We studied the in vivo process by which PDFR signaling turns off, by converting as many as half of the 28 potential sites of phosphorylation in its C terminal tail to a non-phosphorylatable residue (alanine). We report that many such sites are conserved evolutionarily, and their conversion creates a specific behavioral syndrome opposite to loss-of-function phenotypes previously described for pdfr. That syndrome includes increases in the amplitudes of both Morning and Evening behavioral peaks, as well as multi-hour delays of the Evening phase. The precise behavioral effects were dependent on day-length, and most effects mapped to conversion of only a few, specific serine residues near the very end of the protein and specific to its A isoform. Behavioral phase delays of the Evening activity under entraining conditions predicted the phase of activity cycles under constant darkness. The behavioral phenotypes produced by the most severe PDFR variant were ligand-dependent in vivo, and not a consequence of changes to their pharmacological properties, nor of changes in their surface expression, as measured in vitro. The mechanisms underlying termination of PDFR signaling are complex, subject to regulation that is modified by season, and central to a better understanding of the peptidergic modulation of behavior. In multi-cellular organisms, circadian pacemakers create output as a series of phase markers across the 24 hour day to allow other cells to pattern diverse aspects of daily rhythmic physiology and behavior. Within circadian pacemaker circuits, neuropeptide signaling is essential to help promote coherent circadian outputs. In the fruit fly Drosophila 150 neurons are dedicated circadian clocks and they all tell the same time. In spite of such strong synchronization, they provide diverse phasic outputs in the form of their discrete, asynchronous neuronal activity patterns. Neuropeptide signaling breaks the clock-generated symmetry and drives many pacemakers away from their preferred activity period in the morning. Each day, neuropeptide PDF is released by Morning pacemakers and delays the phase of activity of specific other pacemakers to later parts of the day or night. When and how the PDF that is released in the morning stops acting is unknown. Furthermore, timing of signal termination is not fixed because day length changes each day, hence the modulatory delay exerted by PDF must itself be regulated. Here we test a canonical model of G protein-coupled receptor physiology to ask how PDF receptor signaling is normally de-activated. We use behavioral measures to define sequence elements of the receptor whose post-translational modifications (e.g., phosphorylation) may define the duration of receptor signaling.
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Affiliation(s)
- Weihua Li
- Department of Neuroscience, Washington University School of Medicine, St Louis, Missouri, United States of America
| | - Jennifer S. Trigg
- Department of Neuroscience, Washington University School of Medicine, St Louis, Missouri, United States of America
| | - Paul H. Taghert
- Department of Neuroscience, Washington University School of Medicine, St Louis, Missouri, United States of America
- * E-mail:
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Li N, Shan S, Li XQ, Chen TT, Qi M, Zhang SN, Wang ZY, Zhang LL, Wei W, Sun WY. G Protein-Coupled Receptor Kinase 2 as Novel Therapeutic Target in Fibrotic Diseases. Front Immunol 2022; 12:822345. [PMID: 35111168 PMCID: PMC8801426 DOI: 10.3389/fimmu.2021.822345] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Accepted: 12/27/2021] [Indexed: 11/13/2022] Open
Abstract
G protein-coupled receptor kinase 2 (GRK2), an important subtype of GRKs, specifically phosphorylates agonist-activated G protein-coupled receptors (GPCRs). Besides, current research confirms that it participates in multiple regulation of diverse cells via a non-phosphorylated pathway, including interacting with various non-receptor substrates and binding partners. Fibrosis is a common pathophysiological phenomenon in the repair process of many tissues due to various pathogenic factors such as inflammation, injury, drugs, etc. The characteristics of fibrosis are the activation of fibroblasts leading to myofibroblast proliferation and differentiation, subsequent aggerate excessive deposition of extracellular matrix (ECM). Then, a positive feedback loop is occurred between tissue stiffness caused by ECM and fibroblasts, ultimately resulting in distortion of organ architecture and function. At present, GRK2, which has been described as a multifunctional protein, regulates copious signaling pathways under pathophysiological conditions correlated with fibrotic diseases. Along with GRK2-mediated regulation, there are diverse effects on the growth and apoptosis of different cells, inflammatory response and deposition of ECM, which are essential in organ fibrosis progression. This review is to highlight the relationship between GRK2 and fibrotic diseases based on recent research. It is becoming more convincing that GRK2 could be considered as a potential therapeutic target in many fibrotic diseases.
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Affiliation(s)
- Nan Li
- Institute of Clinical Pharmacology, Anhui Medical University, Key Laboratory of Anti-inflammatory and Immune Medicine, Ministry of Education, Collaborative Innovation Center of Anti-inflammatory and Immune Medicine, Hefei, China
| | - Shan Shan
- Institute of Clinical Pharmacology, Anhui Medical University, Key Laboratory of Anti-inflammatory and Immune Medicine, Ministry of Education, Collaborative Innovation Center of Anti-inflammatory and Immune Medicine, Hefei, China
| | - Xiu-Qin Li
- Institute of Clinical Pharmacology, Anhui Medical University, Key Laboratory of Anti-inflammatory and Immune Medicine, Ministry of Education, Collaborative Innovation Center of Anti-inflammatory and Immune Medicine, Hefei, China
| | - Ting-Ting Chen
- Institute of Clinical Pharmacology, Anhui Medical University, Key Laboratory of Anti-inflammatory and Immune Medicine, Ministry of Education, Collaborative Innovation Center of Anti-inflammatory and Immune Medicine, Hefei, China
| | - Meng Qi
- Institute of Clinical Pharmacology, Anhui Medical University, Key Laboratory of Anti-inflammatory and Immune Medicine, Ministry of Education, Collaborative Innovation Center of Anti-inflammatory and Immune Medicine, Hefei, China
| | - Sheng-Nan Zhang
- Institute of Clinical Pharmacology, Anhui Medical University, Key Laboratory of Anti-inflammatory and Immune Medicine, Ministry of Education, Collaborative Innovation Center of Anti-inflammatory and Immune Medicine, Hefei, China
| | - Zi-Ying Wang
- Institute of Clinical Pharmacology, Anhui Medical University, Key Laboratory of Anti-inflammatory and Immune Medicine, Ministry of Education, Collaborative Innovation Center of Anti-inflammatory and Immune Medicine, Hefei, China
| | - Ling-Ling Zhang
- Institute of Clinical Pharmacology, Anhui Medical University, Key Laboratory of Anti-inflammatory and Immune Medicine, Ministry of Education, Collaborative Innovation Center of Anti-inflammatory and Immune Medicine, Hefei, China
| | - Wei Wei
- Institute of Clinical Pharmacology, Anhui Medical University, Key Laboratory of Anti-inflammatory and Immune Medicine, Ministry of Education, Collaborative Innovation Center of Anti-inflammatory and Immune Medicine, Hefei, China
| | - Wu-Yi Sun
- Institute of Clinical Pharmacology, Anhui Medical University, Key Laboratory of Anti-inflammatory and Immune Medicine, Ministry of Education, Collaborative Innovation Center of Anti-inflammatory and Immune Medicine, Hefei, China
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Zhang X, Min X, Zhu A, Kim KM. A novel molecular mechanism involved in the crosstalks between homologous and PKC-mediated heterologous regulatory pathway of dopamine D2 receptor. Biochem Pharmacol 2020; 174:113791. [DOI: 10.1016/j.bcp.2020.113791] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Accepted: 01/02/2020] [Indexed: 11/15/2022]
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Al-Shboul OA, Al-Dwairi AN, Alqudah MA, Mustafa AG. Gender differences in the regulation of MLC 20 phosphorylation and smooth muscle contraction in rat stomach. Biomed Rep 2018; 8:283-288. [PMID: 29599980 DOI: 10.3892/br.2018.1053] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Accepted: 01/19/2018] [Indexed: 01/03/2023] Open
Abstract
Evidence of sex-related differences in gastrointestinal (GI) functions has been reported in the literature. In addition, various GI disorders have disproportionate prevalence between the sexes. An essential step in the initiation of smooth muscle contraction is the phosphorylation of the 20-kDa regulatory myosin light chain (MLC20) by the Ca2+/calmodulin-dependent myosin light chain kinase (MLCK). However, whether male stomach smooth muscle inherits different contractile signaling mechanisms for the regulation of MLC20 phosphorylation from that in females has not been established. The present study was designed to investigate sex-associated differences in the regulation of MLC20 phosphorylation and thus muscle contraction in gastric smooth muscle cells (GSMCs). Experiments were performed on GSMCs freshly isolated from male and female rats. Contraction of the GSMCs in response to acetylcholine (ACh), a muscarinic agonist, was measured via scanning micrometry in the presence or absence of the MLCK inhibitor, ML-7. Additionally, the protein levels of MLC20, MLCK and phosphorylated MLC20 were measured by ELISA. The protein levels of MLC20 and MLCK were indifferent between the sexes. ACh induced greater contraction (P<0.05) as well as greater MLC20 phosphorylation (P<0.05) in male GSMCs compared with female. Pretreatment of GSMCs with ML-7 significantly reduced the ACh-induced contraction (P<0.05) and MLC20 phosphorylation (P<0.05) in the male and female cells, and notably, abolished the contractile differences between the sexes. In conclusion, MLC20 phosphorylation and thus muscle contraction may be activated to a greater extent in male rat stomach compared with that in females.
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Affiliation(s)
- Othman A Al-Shboul
- Department of Physiology and Biochemistry, Faculty of Medicine, Jordan University of Science and Technology, Irbid 22110, Jordan
| | - Ahmed N Al-Dwairi
- Department of Physiology and Biochemistry, Faculty of Medicine, Jordan University of Science and Technology, Irbid 22110, Jordan
| | - Mohammad A Alqudah
- Department of Physiology and Biochemistry, Faculty of Medicine, Jordan University of Science and Technology, Irbid 22110, Jordan
| | - Ayman G Mustafa
- Department of Anatomy, Faculty of Medicine, Jordan University of Science and Technology, Irbid 22110, Jordan
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Shimizu Y, Koyama R, Kawamoto T. Rho kinase-dependent desensitization of GPR39; a unique mechanism of GPCR downregulation. Biochem Pharmacol 2017; 140:105-114. [PMID: 28619258 DOI: 10.1016/j.bcp.2017.06.115] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Accepted: 06/09/2017] [Indexed: 12/14/2022]
Abstract
GPR39, a G-protein-coupled receptor activated by zinc, reportedly activates multiple intracellular signaling pathways via Gs, Gq, G12/13, and β-arrestin, but little is known about downregulation of the receptor upon its activation. To our knowledge, this is the first report on the mechanism of feedback regulation of GPR39 function determined in GPR39-expressing HEK293 cells (HEK293-GPR39) as a model cell system. In HEK293-GPR39 cells, GPR39-C3, which is a positive allosteric modulator, activated cAMP production (downstream of Gs), IP1 accumulation (downstream of Gq), SRF-RE-dependent transcription (downstream of G12/13), and β-arrestin recruitment. GPR39-C3 induced dose- and time-dependent loss of response in cAMP production by second challenge of the compound. This functional desensitization was blocked by the Rho kinase (ROCK) inhibitor, Y-27632, but not by Gq or Gs-pathway inhibitors or inhibition of β-arrestin recruitment. In the receptor localization assay, GPR39-C3 induced internalization of GFP-tagged GPR39. This internalization was also inhibited by Y-27632, which suggested that ROCK activation is critical for internalization and desensitization of GPR39. A novel biased GPR39 positive allosteric modulator, 5-[2-[(2,4-dichlorophenyl)methoxy]phenyl]-2,2-dimethyl-1,3,5,6-tetrahydrobenzo[a]phenanthridin-4-one (GSB-118), which activated cAMP responses and β-arrestin recruitment but showed no effect on SRF-RE-dependent transcription, did not induce desensitization. These results revealed a unique mechanism of desensitization of GPR39.
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Affiliation(s)
- Yuji Shimizu
- Biomolecular Research Laboratories, Pharmaceutical Research Division, Takeda Pharmaceutical Company Limited, 26-1, Muraoka-higashi 2-chome, Fujisawa, Kanagawa 251-8555, Japan.
| | - Ryokichi Koyama
- Biomolecular Research Laboratories, Pharmaceutical Research Division, Takeda Pharmaceutical Company Limited, 26-1, Muraoka-higashi 2-chome, Fujisawa, Kanagawa 251-8555, Japan
| | - Tomohiro Kawamoto
- Biomolecular Research Laboratories, Pharmaceutical Research Division, Takeda Pharmaceutical Company Limited, 26-1, Muraoka-higashi 2-chome, Fujisawa, Kanagawa 251-8555, Japan
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Zhang X, Kim KM. Multifactorial Regulation of G Protein-Coupled Receptor Endocytosis. Biomol Ther (Seoul) 2017; 25:26-43. [PMID: 28035080 PMCID: PMC5207461 DOI: 10.4062/biomolther.2016.186] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2016] [Revised: 11/21/2016] [Accepted: 11/30/2016] [Indexed: 12/26/2022] Open
Abstract
Endocytosis is a process by which cells absorb extracellular materials via the inward budding of vesicles formed from the plasma membrane. Receptor-mediated endocytosis is a highly selective process where receptors with specific binding sites for extracellular molecules internalize via vesicles. G protein-coupled receptors (GPCRs) are the largest single family of plasma-membrane receptors with more than 1000 family members. But the molecular mechanisms involved in the regulation of GPCRs are believed to be highly conserved. For example, receptor phosphorylation in collaboration with β-arrestins plays major roles in desensitization and endocytosis of most GPCRs. Nevertheless, a number of subsequent studies showed that GPCR regulation, such as that by endocytosis, occurs through various pathways with a multitude of cellular components and processes. This review focused on i) functional interactions between homologous and heterologous pathways, ii) methodologies applied for determining receptor endocytosis, iii) experimental tools to determine specific endocytic routes, iv) roles of small guanosine triphosphate-binding proteins in GPCR endocytosis, and v) role of post-translational modification of the receptors in endocytosis.
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Affiliation(s)
- Xiaohan Zhang
- Pharmacology Laboratory, College of Pharmacy, Chonnam National University, Gwangju 61186, Republic of Korea
| | - Kyeong-Man Kim
- Pharmacology Laboratory, College of Pharmacy, Chonnam National University, Gwangju 61186, Republic of Korea
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Al-Shboul O. The role of the RhoA/ROCK pathway in gender-dependent differences in gastric smooth muscle contraction. J Physiol Sci 2016; 66:85-92. [PMID: 26391686 PMCID: PMC10717576 DOI: 10.1007/s12576-015-0400-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2015] [Accepted: 09/07/2015] [Indexed: 12/20/2022]
Abstract
Gender-related differences in various gastric functions and diseases have been reported, with women having a higher prevalence of gastrointestinal disturbances than men. The aim of this study was to investigate sex-dependent differences in activation of the Rho-associated protein kinase (ROCK; RhoA/Rho kinase) pathway and muscle contraction in the stomach using single gastric smooth muscle cells (GSMC) from male and female Sprague-Dawley rats. Expression of ROCK1 and ROCK2 protein and acetylcholine (ACh)-induced activation of RhoA and ROCK were measured using a specifically designed enzyme-linked immunosorbent assay and activity assay kits, respectively. Contraction of a single GSMC was measured by scanning micrometry in the presence or absence of the ROCK inhibitor Y27632 dihydrochloride. ACh-induced activation of RhoA and ROCK and subsequent contraction were greater in male rats than in female rats but neither was related to differences in the expression of ROCK1 or ROCK2 or total RhoA amount. Most important, Y27632 inhibited and abolished differences in ACh-induced contraction in both sexes. In conclusion, increased ACh-induced contraction in the GSMC of male rats is attributable to greater RhoA/ROCK activation independent of differences in the expression of ROCK isoforms or total RhoA.
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Affiliation(s)
- Othman Al-Shboul
- Department of Physiology and Biochemistry, Faculty of Medicine, Jordan University of Science and Technology, Irbid, 22110, Jordan.
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Zheng M, Zhang X, Guo S, Zhang X, Choi HJ, Lee MY, Kim KM. PKCβII inhibits the ubiquitination of β-arrestin2 in an autophosphorylation-dependent manner. FEBS Lett 2015; 589:3929-37. [DOI: 10.1016/j.febslet.2015.10.031] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Revised: 09/07/2015] [Accepted: 10/23/2015] [Indexed: 01/19/2023]
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Nie F, Cao J, Tong J, Zhu M, Gao Y, Ran Z. Role of Raf-kinase inhibitor protein in colorectal cancer and its regulation by hydroxycamptothecine. J Biomed Sci 2015; 22:56. [PMID: 26177829 PMCID: PMC4502602 DOI: 10.1186/s12929-015-0162-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2014] [Accepted: 07/02/2015] [Indexed: 12/15/2022] Open
Abstract
Background Recently accumulated evidence suggests that Raf kinase inhibitor protein (RKIP) participates in regulation of many signaling pathways and plays an important role in tumorigenesis and tumor metastasis. However, studies investigating the role of RKIP in colorectal cancer have not been reported. The aim of this study was to investigate the role of RKIP on colorectal cancer cell differentiation, progression and its correlation with chemosensitivity. Results Immunohistochemical analysis revealed that RKIP expression was higher in non-neoplastic colorectal tissue (NCRCT) and colorectal cancer tissue (CRCT) than that in metastatic lymph node tissue (MLNT) (P <0.05). P-ERK protein expression was higher in MLNT and CRCT than that in NCRCT (P = 0.02). Immunocytochemical analysis further revealed that RKIP expression was higher in the well differentiated cell line SW1116 as compared to that in the poorly differentiated cell line LoVo. Matrigel invasive assay demonstrated that the inhibition of RKIP by short hairpin RNA (shRNA) 271 transfection significantly increased the number of migrated cells (90.67 ± 4.04 vs. 37.33 ± 2.51, P <0.05), whereas over-expression of RKIP by PEBP-1 plasmid transfection significantly suppressed the number of migrated cells (79.24 ± 5.18 vs. 154.33 ± 7.25, P <0.05). Meanwhile, down-regulation of RKIP induced an increase in the cell survival rate by inhibiting apoptosis induced by hydroxycamptothecine. Conclusions RKIP was also found to be associated with cell differentiation, with a higher activity in well differentiated colorectal cancer cells than in poorly differentiated ones. The upregulated expression of RKIP in colorectal cancer cells inhibited cell invasion and metastasis, while downregulation of RKIP reduced chemosensitivity by inhibiting apoptosis induced by HCPT.
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Affiliation(s)
- Fang Nie
- Department of Intensive Care Medicine, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China.
| | - Jianguo Cao
- Department of Intensive Care Medicine, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China.
| | - Jinlu Tong
- Division of Gastroenterology and Hepatology, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai Institute of Digestive Disease, 145 Middle Shandong Road, Shanghai, 200001, China.
| | - Mingming Zhu
- Division of Gastroenterology and Hepatology, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai Institute of Digestive Disease, 145 Middle Shandong Road, Shanghai, 200001, China.
| | - Yuan Gao
- Department of Intensive Care Medicine, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China.
| | - Zhihua Ran
- Division of Gastroenterology and Hepatology, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai Institute of Digestive Disease, 145 Middle Shandong Road, Shanghai, 200001, China.
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Albano GD, Zhao J, Etling EB, Park SY, Hu H, Trudeau JB, Profita M, Wenzel SE. IL-13 desensitizes β2-adrenergic receptors in human airway epithelial cells through a 15-lipoxygenase/G protein receptor kinase 2 mechanism. J Allergy Clin Immunol 2015; 135:1144-53.e1-9. [PMID: 25819984 PMCID: PMC4426258 DOI: 10.1016/j.jaci.2015.02.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2014] [Revised: 02/05/2015] [Accepted: 02/06/2015] [Indexed: 01/09/2023]
Abstract
BACKGROUND β2-Adrenergic receptor (β2AR) agonists are critical treatments for asthma. However, receptor desensitization can lead to loss of therapeutic effects. Although desensitization to repeated use of β2-agonists is well studied, type 2 inflammation could also affect β2AR function. OBJECTIVE We sought to evaluate the effect of the type 2 cytokine IL-13 on β2AR desensitization in human airway epithelial cells (HAECs) and determine whether 15-lipoxygenase-1 (15LO1) binding with phosphatidylethanolamine-binding protein 1 (PEBP1) contributes to desensitization through release of G protein receptor kinase 2 (GRK2). METHODS HAECs in air-liquid interface culture with or without IL-13 (48 hours) or isoproterenol hydrochloride (ISO; 30 minutes) pretreatment were stimulated with ISO (10 minutes). Cyclic adenosine 3, 5-monophosphate (cAMP) levels were measured using ELISA, and β2AR and GRK2 phosphorylation was measured using Western blotting. Short interfering RNA was used for 15LO1 knockdown. Interactions of GRK2, PEBP1, and 15LO1 were detected by means of immunoprecipitation/Western blotting and immunofluorescence. HAECs and airway tissue from control subjects and asthmatic patients were evaluated for I5LO1, PEBP1, and GRK2. RESULTS Pretreatment with ISO or IL-13 decreased ISO-induced cAMP generation compared with ISO for 10 minutes alone paralleled by increases in β2AR and GRK2 phosphorylation. GRK2 associated with PEBP1 after 10 minutes of ISO in association with low phosphorylated GRK2 (pGRK2) levels. In contrast, in the presence of IL-13 plus ISO (10 minutes), binding of GRK2 to PEBP1 decreased, whereas 15LO1 binding and pGRK2 levels increased. 15LO1 knockdown restored ISO-induced cAMP generation. These findings were recapitulated in freshly brushed HAECs from cells and tissue of asthmatic patients. CONCLUSION IL-13 treatment of HAECs leads to β2AR desensitization, which involves 15LO1/PEBP1 interactions to free GRK2, and allows it to phosphorylate (and desensitize) β2ARs, suggesting that the beneficial effects of β2-agonists could be blunted in patients with type 2 associated asthma.
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Affiliation(s)
- Giusy D Albano
- University of Pittsburgh Asthma Institute at UPMC, Division of Pulmonary, Allergy and Critical Care Medicine, University of Pittsburgh, Pittsburgh, Pa; Institute of Biomedicine and Molecular Immunology, Italian National Research Council, Palermo, Italy
| | - Jinming Zhao
- University of Pittsburgh Asthma Institute at UPMC, Division of Pulmonary, Allergy and Critical Care Medicine, University of Pittsburgh, Pittsburgh, Pa.
| | - Emily B Etling
- University of Pittsburgh Asthma Institute at UPMC, Division of Pulmonary, Allergy and Critical Care Medicine, University of Pittsburgh, Pittsburgh, Pa
| | - Seo Young Park
- Center for Research on Health Care Data Center, University of Pittsburgh, Pittsburgh, Pa
| | - Haizhen Hu
- University of Pittsburgh Asthma Institute at UPMC, Division of Pulmonary, Allergy and Critical Care Medicine, University of Pittsburgh, Pittsburgh, Pa
| | - John B Trudeau
- University of Pittsburgh Asthma Institute at UPMC, Division of Pulmonary, Allergy and Critical Care Medicine, University of Pittsburgh, Pittsburgh, Pa
| | - Mirella Profita
- Institute of Biomedicine and Molecular Immunology, Italian National Research Council, Palermo, Italy
| | - Sally E Wenzel
- University of Pittsburgh Asthma Institute at UPMC, Division of Pulmonary, Allergy and Critical Care Medicine, University of Pittsburgh, Pittsburgh, Pa
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Al-Shboul O, Mustafa A. Effect of oxidative stress on Rho kinase II and smooth muscle contraction in rat stomach. Can J Physiol Pharmacol 2015; 93:405-11. [PMID: 25752964 DOI: 10.1139/cjpp-2014-0505] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Recent studies have shown that both Rho kinase signaling and oxidative stress are involved in the pathogenesis of a number of human diseases, such as diabetes mellitus, hypertension, and atherosclerosis. However, very little is known about the effect of oxidative stress on the gastrointestinal (GI) smooth muscle Rho kinase pathway. The aim of the current study was to investigate the effect of oxidative stress on Rho kinase II and muscle contraction in rat stomach. The peroxynitrite donor 3-morpholinosydnonimine (SIN-1), hydrogen peroxide (H2O2), and peroxynitrite were used to induce oxidative stress. Rho kinase II expression and ACh-induced activity were measured in control and oxidant-treated cells via specifically designed enzyme-linked immunosorbent assay (ELISA) and activity assay kits, respectively. Single smooth muscle cell contraction was measured via scanning micrometry in the presence or absence of the Rho kinase blocker, Y-27632 dihydrochloride. All oxidant agents significantly increased ACh-induced Rho kinase II activity without affecting its expression level. Most important, oxidative stress induced by all three agents augmented ACh-stimulated muscle cell contraction, which was significantly inhibited by Y-27632. In conclusion, oxidative stress activates Rho kinase II and enhances contraction in rat gastric muscle, suggesting an important role in GI motility disorders associated with oxidative stress.
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Affiliation(s)
- Othman Al-Shboul
- Department of physiology and biochemistry, Faculty of Medicine, Jordan University of Science and Technology, Irbid 22110, Jordan
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Arthur S, Sundaram U. Protein kinase C-mediated phosphorylation of RKIP regulates inhibition of Na-alanine cotransport by leukotriene D(4) in intestinal epithelial cells. Am J Physiol Cell Physiol 2014; 307:C1010-6. [PMID: 25231108 DOI: 10.1152/ajpcell.00284.2014] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Leukotriene D4 (LTD4) is an important immune inflammatory mediator that is known to be elevated in the mucosa of chronically inflamed intestine and alter nutrient absorption. LTD4 inhibits Na-alanine cotransport in intestinal epithelial cells by decreasing the affinity of the cotransporter ASCT1. LTD4 is known to increase intracellular Ca(++) and cAMP concentrations. However, the intracellular signaling mechanism of LTD4-mediated ASCT1 inhibition is unknown. In the present study, pretreatment with calcium chelator BAPTA-AM or inhibition of Ca(++)-dependent protein kinase C (PKC), specifically PKCα, resulted in the reversal of LTD4-mediated inhibition of ASCT1, revealing the involvement of the Ca(++)-activated PKC pathway. PKCα is known to phosphorylate Raf kinase inhibitor protein (RKIP), thus activating its downstream signaling pathway. Immunoblotting with anti-RKIP-Ser(153) antibody showed an increase in phosphorylation levels of RKIP in LTD4-treated cells. Downregulation of endogenous RKIP showed no decrease in ASCT1 activity by LTD4, thus confirming its involvement in ASCT1 regulation. Phosphorylation of RKIP by PKC is known to activate different signaling pathways, and in this study it was found to activate cAMP-activated protein kinase A (PKA) pathway. Although protein abundance of ASCT1 was not altered in any of the experimental conditions, there was an increase in the levels of phosphothreonine in ASCT1 protein, thus showing that phosphorylation changes were responsible for the altered affinity of ASCT1 by LTD4. In conclusion, LTD4 inhibits ASCT1 through PKC-mediated phosphorylation of RKIP, leading to the subsequent activation of PKA pathway, possibly through β2-andrenergic receptor activation.
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Affiliation(s)
- Subha Arthur
- Department of Clinical and Translational Sciences, Joan C. Edwards School of Medicine, Marshall University, Huntington, West Virginia
| | - Uma Sundaram
- Department of Clinical and Translational Sciences, Joan C. Edwards School of Medicine, Marshall University, Huntington, West Virginia
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Mahavadi S, Sriwai W, Huang J, Grider JR, Murthy KS. Inhibitory signaling by CB1 receptors in smooth muscle mediated by GRK5/β-arrestin activation of ERK1/2 and Src kinase. Am J Physiol Gastrointest Liver Physiol 2014; 306:G535-45. [PMID: 24407588 PMCID: PMC3949025 DOI: 10.1152/ajpgi.00397.2013] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
We examined whether CB1 receptors in smooth muscle conform to the signaling pattern observed with other Gi-coupled receptors that stimulate contraction via two Gβγ-dependent pathways (PLC-β3 and phosphatidylinositol 3-kinase/integrin-linked kinase). Here we show that the anticipated Gβγ-dependent signaling was abrogated. Except for inhibition of adenylyl cyclase via Gαi, signaling resulted from Gβγ-independent phosphorylation of CB1 receptors by GRK5, recruitment of β-arrestin1/2, and activation of ERK1/2 and Src kinase. Neither uncoupling of CB1 receptors from Gi by pertussis toxin (PTx) or Gi minigene nor expression of a Gβγ-scavenging peptide had any effect on ERK1/2 activity. The latter was abolished in muscle cells expressing β-arrestin1/2 siRNA. CB1 receptor internalization and both ERK1/2 and Src kinase activities were abolished in cells expressing kinase-deficient GRK5(K215R). Activation of ERK1/2 and Src kinase endowed CB1 receptors with the ability to inhibit concurrent contractile activity. We identified a consensus sequence (102KSPSKLSP109) for phosphorylation of RGS4 by ERK1/2 and showed that expression of a RGS4 mutant lacking Ser103/Ser108 blocked the ability of anandamide to inhibit acetylcholine-mediated phosphoinositide hydrolysis or enhance Gαq:RGS4 association and inactivation of Gαq. Activation of Src kinase by anandamide enhanced both myosin phosphatase RhoA-interacting protein (M-RIP):RhoA and M-RIP:MYPT1 association and inhibited Rho kinase activity, leading to increase of myosin light chain (MLC) phosphatase activity and inhibition of sustained muscle contraction. Thus, unlike other Gi-coupled receptors in smooth muscle, CB1 receptors did not engage Gβγ but signaled via GRK5/β-arrestin activation of ERK1/2 and Src kinase: ERK1/2 accelerated inactivation of Gαq by RGS4, and Src kinase enhanced MLC phosphatase activity, leading to inhibition of ACh-stimulated contraction.
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Affiliation(s)
- Sunila Mahavadi
- Department of Physiology and Biophysics, VCU Program in Enteric Neuromuscular Sciences, Virginia Commonwealth University, Richmond, Virginia
| | - Wimolpak Sriwai
- Department of Physiology and Biophysics, VCU Program in Enteric Neuromuscular Sciences, Virginia Commonwealth University, Richmond, Virginia
| | - Jiean Huang
- Department of Physiology and Biophysics, VCU Program in Enteric Neuromuscular Sciences, Virginia Commonwealth University, Richmond, Virginia
| | - John R. Grider
- Department of Physiology and Biophysics, VCU Program in Enteric Neuromuscular Sciences, Virginia Commonwealth University, Richmond, Virginia
| | - Karnam S. Murthy
- Department of Physiology and Biophysics, VCU Program in Enteric Neuromuscular Sciences, Virginia Commonwealth University, Richmond, Virginia
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Langer I. Mechanisms involved in VPAC receptors activation and regulation: lessons from pharmacological and mutagenesis studies. Front Endocrinol (Lausanne) 2012; 3:129. [PMID: 23115557 PMCID: PMC3483716 DOI: 10.3389/fendo.2012.00129] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2012] [Accepted: 10/11/2012] [Indexed: 11/18/2022] Open
Abstract
Vasoactive intestinal peptide (VIP) plays diverse and important role in human physiology and physiopathology and their receptors constitute potential targets for the treatment of several diseases such as neurodegenerative disorder, asthma, diabetes, and inflammatory diseases. This article reviews the current knowledge regarding the two VIP receptors, VPAC(1) and VPAC(2), with respect to mechanisms involved in receptor activation, G protein coupling, signaling, regulation, and oligomerization.
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Affiliation(s)
- Ingrid Langer
- Institut de Recherche Interdisciplinaire en Biologie Humaine et Moléculaire, Faculté de Médecine, Université Libre de BruxellesBrussels, Belgium
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16
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Kim SO, Ives KL, Wang X, Davey RA, Chao C, Hellmich MR. Raf-1 kinase inhibitory protein (RKIP) mediates ethanol-induced sensitization of secretagogue signaling in pancreatic acinar cells. J Biol Chem 2012; 287:33377-88. [PMID: 22859298 DOI: 10.1074/jbc.m112.367656] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Excessive alcohol consumption is associated with most cases of chronic pancreatitis, a progressive necrotizing inflammatory disease that can result in pancreatic insufficiency due to acinar atrophy and fibrosis and an increased risk of pancreatic cancer. At a cellular level acute alcohol exposure can sensitize pancreatic acinar cells to secretagogue stimulation, resulting in dysregulation of intracellular Ca(2+) homeostasis and premature digestive enzyme activation; however, the molecular mechanisms by which ethanol exerts these toxic effects have remained undefined. In this study we identify Raf-1 kinase inhibitory protein as an essential mediator of ethanol-induced sensitization of cholecystokinin- and carbachol-regulated Ca(2+) signaling in pancreatic acinar cells. We show that exposure of rodent acinar cells to ethanol induces protein kinase C-dependent Raf-1 kinase inhibitory protein phosphorylation, sensitization of cholecystokinin-stimulated Ca(2+) signaling, and potentiation of both basal and cholecystokinin-stimulated extracellular signal-regulated kinase activation. Furthermore, we show that either suppression of Raf-1 kinase inhibitory protein expression using short hairpin RNA or gene ablation prevented the sensitizing effects of ethanol on cholecystokinin- and carbachol-stimulated Ca(2+) signaling and intracellular chymotrypsin activation in pancreatic acinar cells, suggesting that the modulation of Raf-1 inhibitory protein expression may have future therapeutic utility in the prevention or treatment of alcohol-associated pancreatitis.
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Affiliation(s)
- Sung Ok Kim
- Department of Surgery, University of Texas Medical Branch, Galveston, Texas 77555-0722, USA
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Deiss K, Kisker C, Lohse MJ, Lorenz K. Raf kinase inhibitor protein (RKIP) dimer formation controls its target switch from Raf1 to G protein-coupled receptor kinase (GRK) 2. J Biol Chem 2012; 287:23407-17. [PMID: 22610096 DOI: 10.1074/jbc.m112.363812] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Proteins controlling cellular networks have evolved distinct mechanisms to ensure specificity in protein-protein interactions. Raf kinase inhibitor protein (RKIP) is a multifaceted kinase modulator, but it is not well understood how this small protein (21 kDa) can coordinate its diverse signaling functions. Raf1 and G protein-coupled receptor kinase (GRK) 2 are direct interaction partners of RKIP and thus provide the possibility to untangle the mechanism of its target specificity. Here, we identify RKIP dimer formation as an important mechanistic feature in the target switch from Raf1 to GRK2. Co-immunoprecipitation and cross-linking experiments revealed RKIP dimerization upon phosphorylation of RKIP at serine 153 utilizing purified proteins as well as in cells overexpressing RKIP. A functional phosphomimetic RKIP mutant had a high propensity for dimerization and reproduced the switch from Raf1 to GRK2. RKIP dimerization and GRK2 binding, but not Raf1 interaction, were prevented by a peptide comprising amino acids 127-146 of RKIP, which suggests that this region is critical for dimer formation. Furthermore, a dimeric RKIP mutant displayed a higher affinity to GRK2, but a lower affinity to Raf1. Functional analyses of phosphomimetic as well as dimeric RKIP demonstrated that enhanced dimerization of RKIP translates into decreased Raf1 and increased GRK2 inhibition. The detection of RKIP dimers in a complex with GRK2 in murine hearts implies their physiological relevance. These findings represent a novel mechanistic feature how RKIP can discriminate between its different interaction partners and thus advances our understanding how specific inhibition of kinases can be achieved.
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Affiliation(s)
- Katharina Deiss
- Institute of Pharmacology and Toxicology, University of Wuerzburg, Versbacher Strasse 9, 97078 Wuerzburg, Germany
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Morecroft I, Doyle B, Nilsen M, Kolch W, Mair K, Maclean MR. Mice lacking the Raf-1 kinase inhibitor protein exhibit exaggerated hypoxia-induced pulmonary hypertension. Br J Pharmacol 2011; 163:948-63. [PMID: 21385176 DOI: 10.1111/j.1476-5381.2011.01305.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
BACKGROUND AND PURPOSE Increased pulmonary vascular remodelling, pulmonary arterial pressure and pulmonary vascular resistance characterize the development of pulmonary arterial hypertension (PAH). Activation of the Raf/mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK)1/2 is thought to play an important role in PAH and Raf-1 kinase inhibitor protein (RKIP), negatively regulates this pathway. This study investigated whether genetic deletion of RKIP (and hence ERK1/2 up-regulation) resulted in a pulmonary hypertensive phenotype in mice and investigated a role for RKIP in mitogen-regulated proliferative responses in lung fibroblasts. EXPERIMENTAL APPROACH Pulmonary vascular haemodynamics and remodelling were assessed in mice genetically deficient in RKIP (RKIP-/-) after 2 weeks of either normoxia or hypoxia. Immunoblotting and immunohistochemistry were used to examine phosphorylation of Raf-1, RKIP and ERK1/2 in mouse pulmonary arteries. In vitro, RKIP inhibition of mitogen signalling was analysed in CCL39 hamster lung fibroblasts. KEY RESULTS RKIP-/- mice demonstrated elevated indices of PAH and ERK1/2 phosphorylation compared with wild-type (WT) mice. Hypoxic RKIP-/- mice exhibited exaggerated PAH indices. Hypoxia increased phosphorylation of Raf-1, RKIP and ERK1/2 in WT mouse pulmonary arteries and Raf-1 phosphorylation in RKIP-/- mouse pulmonary arteries. In CCL39 cells, inhibition of RKIP potentiated mitogen-induced proliferation and phosphorylation of RKIP, and Raf-1. CONCLUSIONS AND IMPLICATIONS The lack of RKIP protein resulted in a pulmonary hypertensive phenotype, exaggerated in hypoxia. Hypoxia induced phosphorylation of RKIP signalling elements in WT pulmonary arteries. RKIP inhibition potentiated mitogen-induced proliferation in lung fibroblasts. These results provide evidence for the involvement of RKIP in suppressing the development of hypoxia-induced PAH in mice.
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Affiliation(s)
- I Morecroft
- Institute of Cardiovascular & Medical Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK.
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Huerta-Yepez S, Yoon NK, Hernandez-Cueto A, Mah V, Rivera-Pazos CM, Chatterjee D, Vega MI, Maresh EL, Horvath S, Chia D, Bonavida B, Goodglick L. Expression of phosphorylated raf kinase inhibitor protein (pRKIP) is a predictor of lung cancer survival. BMC Cancer 2011; 11:259. [PMID: 21689459 PMCID: PMC3134426 DOI: 10.1186/1471-2407-11-259] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2010] [Accepted: 06/21/2011] [Indexed: 12/03/2022] Open
Abstract
Background Raf-1 kinase inhibitor protein (RKIP) has been reported to negatively regulate signal kinases of major survival pathways. RKIP activity is modulated in part by phosphorylation on Serine 153 by protein kinase C, which leads to dissociation of RKIP from Raf-1. RKIP expression is low in many human cancers and represents an indicator of poor prognosis and/or induction of metastasis. The prognostic power has typically been based on total RKIP expression and has not considered the significance of phospho-RKIP. Methods The present study examined the expression levels of both RKIP and phospho-RKIP in human lung cancer tissue microarray proteomics technology. Results Total RKIP and phospho-RKIP expression levels were similar in normal and cancerous tissues. phospho-RKIP levels slightly decreased in metastatic lesions. However, the expression levels of phospho-RKIP, in contrast to total RKIP, displayed significant predictive power for outcome with normal expression of phospho-RKIP predicting a more favorable survival compared to lower levels (P = 0.0118); this was even more pronounced in more senior individuals and in those with early stage lung cancer. Conclusions This study examines for the first time, the expression profile of RKIP and phospho-RKIP in lung cancer. Significantly, we found that phospho-RKIP was a predictive indicator of survival.
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Affiliation(s)
- Sara Huerta-Yepez
- Unidad de Investigacion en Enferemedades Oncologicas, Hospital Infantil de Mexico, Federico Gomez, SSa, Mexico
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20
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Bibliography. Current world literature. Growth and development. Curr Opin Endocrinol Diabetes Obes 2008; 15:79-101. [PMID: 18185067 DOI: 10.1097/med.0b013e3282f4f084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Langer I, Robberecht P. Molecular mechanisms involved in vasoactive intestinal peptide receptor activation and regulation: current knowledge, similarities to and differences from the A family of G-protein-coupled receptors. Biochem Soc Trans 2007; 35:724-8. [PMID: 17635134 DOI: 10.1042/bst0350724] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
An actual paradigm for activation and regulation of the GPCR (G-protein-coupled receptors)/seven-transmembrane helix family of receptors essentially emerges from extensive studies of the largest family of receptors, the GPCR-A/rhodopsin family. The mechanisms regulating the GPCR-B family signal transduction are less precisely understood due in part to the lack of the conserved signatures of the GPCR-A family (E/DRY, NPXXY) and in part to the absence of a reliable receptor modelling, although some studies suggest that both families share similar features. Here, we try to highlight the current knowledge of the activation and the regulation of the VIP (vasoactive intestinal peptide) receptors, namely VPAC (VIP/pituitary adenylate cyclase-activating peptide receptor) 1 and 2. This includes search for amino acids involved in the stabilization of the receptor active conformation and in coupling to G-proteins, signalling pathways activated in response to VIP, agonist-dependent receptor down-regulation, phosphorylation and internalization as well as pharmacological consequences of receptor hetero-dimerization.
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Affiliation(s)
- I Langer
- Laboratory of Biological Chemistry and Nutrition, Faculty of Medicine, Université Libre de Bruxelles, 808 route de Lennik CP 611, B-1070 Brussels, Belgium.
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