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Abstract
The GNA15 gene is ectopically expressed in human pancreatic ductal adenocarcinoma cancer cells. The encoded Gα15 protein can promiscuously redirect GPCR signaling toward pathways with oncogenic potential. We sought to describe the distribution of GNA15 in adenocarcinoma from human pancreatic specimens and to analyze the mechanism driving abnormal expression and the consequences on signaling and clinical follow-up. We detected GNA15 expression in pre-neoplastic pancreatic lesions and throughout progression. The analysis of biological data sets, primary and xenografted human tumor samples, and clinical follow-up shows that elevated expression is associated with poor prognosis for GNA15, but not any other GNA gene. Demethylation of the 5′ GNA15 promoter region was associated with ectopic expression of Gα15 in pancreatic neoplastic cells, but not in adjacent dysplastic or non-transformed tissue. Down-modulation of Gα15 by shRNA or CRISPR/Cas9 affected oncogenic signaling, and reduced adenocarcimoma cell motility and invasiveness. We conclude that de novo expression of wild-type GNA15 characterizes transformed pancreatic cells. The methylation pattern of GNA15 changes in preneoplastic lesions coincident with the release a transcriptional blockade that allows ectopic expression to persist throughout PDAC progression. Elevated GNA15 mRNA correlates with poor prognosis. In addition, ectopic Gα15 signaling provides an unprecedented mechanism in the early steps of pancreas carcinogenesis distinct from classical G protein oncogenic mutations described previously in GNAS and GNAQ/GNA11.
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Activin-A Induces Early Differential Gene Expression Exclusively in Periodontal Ligament Fibroblasts from Fibrodysplasia Ossificans Progressiva Patients. Biomedicines 2021; 9:biomedicines9060629. [PMID: 34205844 PMCID: PMC8229991 DOI: 10.3390/biomedicines9060629] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Revised: 05/17/2021] [Accepted: 05/28/2021] [Indexed: 01/11/2023] Open
Abstract
Fibrodysplasia Ossificans Progressiva (FOP) is a rare genetic disease characterized by heterotopic ossification (HO). It is caused by mutations in the Activin receptor type 1 (ACVR1) gene, resulting in enhanced responsiveness to ligands, specifically to Activin-A. Though it has been shown that capturing Activin-A protects against heterotopic ossification in animal models, the exact underlying mechanisms at the gene expression level causing ACVR1 R206H-mediated ossifications and progression are thus far unknown. We investigated the early transcriptomic changes induced by Activin-A of healthy control and patient-derived periodontal ligament fibroblasts (PLF) isolated from extracted teeth by RNA sequencing analysis. To study early differences in response to Activin-A, periodontal ligament fibroblasts from six control teeth and from six FOP patient teeth were cultured for 24 h without and with 50 ng/mL Activin-A and analyzed with RNA sequencing. Pathway analysis on genes upregulated by Activin-A in FOP cells showed an association with pathways involved in, among others, Activin, TGFβ, and BMP signaling. Differential gene expression induced by Activin-A was exclusively seen in the FOP cells. Median centered supervised gene expression analysis showed distinct clusters of up- and downregulated genes in the FOP cultures after stimulation with Activin-A. The upregulated genes with high fold changes like SHOC2, TTC1, PAPSS2, DOCK7, and LOX are all associated with bone metabolism. Our open-ended approach to investigating the early effect of Activin-A on gene expression in control and FOP PLF shows that the molecule exclusively induces differential gene expression in FOP cells and not in control cells.
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Yan J, Zuo G, Sherchan P, Huang L, Ocak U, Xu W, Travis ZD, Wang W, Zhang JH, Tang J. CCR1 Activation Promotes Neuroinflammation Through CCR1/TPR1/ERK1/2 Signaling Pathway After Intracerebral Hemorrhage in Mice. Neurotherapeutics 2020; 17:1170-1183. [PMID: 31898284 PMCID: PMC7609528 DOI: 10.1007/s13311-019-00821-5] [Citation(s) in RCA: 44] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The activation of C-C chemokine receptor type 1 (CCR1) has been shown to be pro-inflammatory in several animal models of neurological diseases. The objective of this study was to investigate the activation of CCR1 on neuroinflammation in a mouse model of intracerebral hemorrhage (ICH) and the mechanism of CCR1/tetratricopeptide repeat 1 (TPR1)/extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathway in CCR1-mediated neuroinflammation. Adult male CD1 mice (n = 210) were used in the study. The selective CCR1 antagonist Met-RANTES was administered intranasally at 1 h after autologous blood injection. To elucidate potential mechanism, a specific ERK1/2 activator (ceramide C6) was administered prior to Met-RANTES treatment; CCR1 activator (recombinant CCL5, rCCL5) and TPR1 CRISPR were administered in naïve mouse. Neurobehavioral assessments, brain water content, immunofluorescence staining, and western blot were performed. The endogenous expressions of CCR1, CCL5, TPR1, and p-ERK1/2 were increased in the brain after ICH. CCR1 were expressed on microglia, neurons, and astrocytes. The inhibition of CCR1 with Met-RANTES improved neurologic function, decreased brain edema, and suppressed microglia/macrophage activations and neutrophil infiltration after ICH. Met-RANTES treatment decreased expressions of CCR1, TPR1, p-ERK, TNF-α, and IL-1β, which was reversed by ceramide C6. The brain CCR1 activation by rCCL5 injection in naïve mouse resulted in neurological deficits and increased expressions of CCR1, TPR1, p-ERK, TNF-α, and IL-1β. These detrimental effects of rCCL5 were reversed by TPR1 knockdown using TPR1 CRISPR. Our study demonstrated that CCR1 activation promoted neuroinflammation through CCR1/TPR1/ERK1/2 signaling pathway after ICH in mice. CCR1 inhibition with Met-RANTES attenuated neuroinflammation, thereby reducing brain edema and improving neurobehavioral functions. Targeting CCR1 activation may provide a promising therapeutic approach in the management of ICH patients.
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Affiliation(s)
- Jun Yan
- Department of Neurosurgery, Guangxi Medical University Cancer Hospital, Nanning, 530021, Guangxi, China
- Department of Physiology and Pharmacology, School of Medicine, Loma Linda University, 11041 Campus Street, Loma Linda, CA, 92354, USA
| | - Gang Zuo
- Department of Physiology and Pharmacology, School of Medicine, Loma Linda University, 11041 Campus Street, Loma Linda, CA, 92354, USA
- Department of Neurosurgery, The Affiliated Taicang Hospital, Soochow University, Taicang, Suzhou, 215400, Jiangsu, China
| | - Prativa Sherchan
- Department of Physiology and Pharmacology, School of Medicine, Loma Linda University, 11041 Campus Street, Loma Linda, CA, 92354, USA
| | - Lei Huang
- Department of Physiology and Pharmacology, School of Medicine, Loma Linda University, 11041 Campus Street, Loma Linda, CA, 92354, USA
- Department of Neurosurgery, School of Medicine, Loma Linda University, Loma Linda, CA, 92354, USA
| | - Umut Ocak
- Department of Physiology and Pharmacology, School of Medicine, Loma Linda University, 11041 Campus Street, Loma Linda, CA, 92354, USA
| | - Weilin Xu
- Department of Physiology and Pharmacology, School of Medicine, Loma Linda University, 11041 Campus Street, Loma Linda, CA, 92354, USA
| | - Zachary D Travis
- Department of Physiology and Pharmacology, School of Medicine, Loma Linda University, 11041 Campus Street, Loma Linda, CA, 92354, USA
- Department of Earth and Biological Sciences, Loma Linda University, Loma Linda, CA, 92350, USA
| | - Wenna Wang
- Department of Physiology and Pharmacology, School of Medicine, Loma Linda University, 11041 Campus Street, Loma Linda, CA, 92354, USA
| | - John H Zhang
- Department of Physiology and Pharmacology, School of Medicine, Loma Linda University, 11041 Campus Street, Loma Linda, CA, 92354, USA
- Department of Neurosurgery, School of Medicine, Loma Linda University, Loma Linda, CA, 92354, USA
- Department of Anesthesiology, School of Medicine, Loma Linda University, Loma Linda, CA, 92354, USA
| | - Jiping Tang
- Department of Physiology and Pharmacology, School of Medicine, Loma Linda University, 11041 Campus Street, Loma Linda, CA, 92354, USA.
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Rodríguez M, Márquez S, Montero O, Alonso S, Frade JG, Crespo MS, Fernández N. Pharmacological inhibition of eicosanoids and platelet-activating factor signaling impairs zymosan-induced release of IL-23 by dendritic cells. Biochem Pharmacol 2015; 102:78-96. [PMID: 26673542 DOI: 10.1016/j.bcp.2015.12.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2015] [Accepted: 12/02/2015] [Indexed: 12/13/2022]
Abstract
The engagement of the receptors for fungal patterns induces the expression of cytokines, the release of arachidonic acid, and the production of PGE2 in human dendritic cells (DC), but few data are available about other lipid mediators that may modulate DC function. The combined antagonism of leukotriene (LT) B4, cysteinyl-LT, and platelet-activating factor (PAF, 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) inhibited IL23A mRNA expression in response to the fungal surrogate zymosan and to a lower extent TNFA (tumor necrosis factor-α) and CSF2 (granulocyte macrophage colony-stimulating factor) mRNA. The combination of lipid mediators and the lipid extract of zymosan-conditioned medium increased the induction of IL23A by LPS (bacterial lipopolysaccharide), thus suggesting that unlike LPS, zymosan elicits the production of mediators at a concentration enough for optimal response. Zymosan induced the release of LTB4, LTE4, 12-hydroxyeicosatetraenoic acid (12-HETE), and PAF C16:0. DC showed a high expression and detectable Ser663 phosphorylation of 5-lipoxygenase in response to zymosan, and a high expression and activity of LPCAT1/2 (lysophosphatidylcholine acyltransferase 1 and 2), the enzymes that incorporate acetate from acetyl-CoA into choline-containing lysophospholipids to produce PAF. Pharmacological modulation of the arachidonic acid cascade and the PAF receptor inhibited the binding of P-71Thr-ATF2 (activating transcription factor 2) to the IL23A promoter, thus mirroring their effects on the expression of IL23A mRNA and IL-23 protein. These results indicate that LTB4, cysteinyl-LT, and PAF, acting through their cognate G protein-coupled receptors, contribute to the phosphorylation of ATF2 and play a central role in IL23A promoter trans-activation and the cytokine signature induced by fungal patterns.
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Affiliation(s)
- Mario Rodríguez
- Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Universidad de Valladolid, 47005 Valladolid, Spain
| | - Saioa Márquez
- Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Universidad de Valladolid, 47005 Valladolid, Spain
| | - Olimpio Montero
- Centro para el Desarrollo de la Biotecnología, CSIC, Parque Tecnológico de Boecillo, Valladolid, Spain
| | - Sara Alonso
- Instituto de Biología y Genética Molecular, CSIC, 47003 Valladolid, Spain
| | - Javier García Frade
- Servicio de Hematología, Hospital Universitario Rio-Hortega, 47012 Valladolid, Spain
| | | | - Nieves Fernández
- Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Universidad de Valladolid, 47005 Valladolid, Spain
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Kwan DHT, Wong KM, Chan ASL, Yung LY, Wong YH. An intact helical domain is required for Gα14 to stimulate phospholipase Cβ. BMC STRUCTURAL BIOLOGY 2015; 15:18. [PMID: 26377666 PMCID: PMC4573470 DOI: 10.1186/s12900-015-0043-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Accepted: 08/26/2015] [Indexed: 11/17/2022]
Abstract
Background Stimulation of phospholipase Cβ (PLCβ) by the activated α-subunit of Gq (Gαq) constitutes a major signaling pathway for cellular regulation, and structural studies have recently revealed the molecular interactions between PLCβ and Gαq. Yet, most of the PLCβ-interacting residues identified on Gαq are not unique to members of the Gαq family. Molecular modeling predicts that the core PLCβ-interacting residues located on the switch regions of Gαq are similarly positioned in Gαz which does not stimulate PLCβ. Using wild-type and constitutively active chimeras constructed between Gαz and Gα14, a member of the Gαq family, we examined if the PLCβ-interacting residues identified in Gαq are indeed essential. Results Four chimeras with the core PLCβ-interacting residues composed of Gαz sequences were capable of binding PLCβ2 and stimulating the formation of inositol trisphosphate. Surprisingly, all chimeras with a Gαz N-terminal half failed to functionally associate with PLCβ2, despite the fact that many of them contained the core PLCβ-interacting residues from Gα14. Further analyses revealed that the non-PLCβ2 interacting chimeras were capable of interacting with other effector molecules such as adenylyl cyclase and tetratricopeptide repeat 1, indicating that they could adopt a GTP-bound active conformation. Conclusion Collectively, our study suggests that the previously identified PLCβ-interacting residues are insufficient to ensure productive interaction of Gα14 with PLCβ, while an intact N-terminal half of Gα14 is apparently required for PLCβ interaction. Electronic supplementary material The online version of this article (doi:10.1186/s12900-015-0043-3) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Dawna H T Kwan
- Division of Life Science and the Biotechnology Research Institute, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
| | - Ka M Wong
- Division of Life Science and the Biotechnology Research Institute, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
| | - Anthony S L Chan
- Division of Life Science and the Biotechnology Research Institute, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
| | - Lisa Y Yung
- Division of Life Science and the Biotechnology Research Institute, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
| | - Yung H Wong
- Division of Life Science and the Biotechnology Research Institute, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong. .,State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
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Tse MK, Morris CJ, Zhang M, Wong YH. Activator of G protein signaling 3 forms a complex with resistance to inhibitors of cholinesterase-8A without promoting nucleotide exchange on Gα(i3). Mol Cell Biochem 2014; 401:27-38. [PMID: 25480567 DOI: 10.1007/s11010-014-2289-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Accepted: 11/26/2014] [Indexed: 01/04/2023]
Abstract
Activator of G protein signaling 3 (AGS3) is a guanine nucleotide dissociation inhibitor (GDI) which stabilizes the Gα(i/o) subunits as an AGS3/Gα(i/o)-GDP complex. It has recently been demonstrated in reconstitution experiments that the AGS3/Gα(i/o)-GDP complex may act as a substrate of resistance to inhibitors of cholinesterase 8A (Ric-8A), a guanine exchange factor (GEF) for heterotrimeric Gα proteins. Since the ability of Ric-8A to activate Gα(i/o) subunits that are bound to AGS3 in a cellular environment has not been confirmed, we thus examined the effect of Ric-8A on cAMP accumulation in HEK293 cells expressing different forms of AGS3 and Gα(i3). Co-immunoprecipitation assays indicate that full-length AGS3 and its N- and C-terminal truncated mutants can interact with Ric-8A in HEK293 cells. Yeast two-hybrid assay further confirmed that Ric-8A can directly bind to AGS3S, a short form of AGS3 which is endogenously expressed in heart. However, Ric-8A failed to facilitate Gα(i)-induced suppression of adenylyl cyclase, suggesting that it may not serve as a GEF for AGS3/Gα(i/o)-GDP complex in a cellular environment.
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Affiliation(s)
- Man K Tse
- Division of Life Science and the Biotechnology Research Institute, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
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Battaglia A, Doccini V, Bernardini L, Novelli A, Loddo S, Capalbo A, Filippi T, Carey JC. Confirmation of chromosomal microarray as a first-tier clinical diagnostic test for individuals with developmental delay, intellectual disability, autism spectrum disorders and dysmorphic features. Eur J Paediatr Neurol 2013; 17:589-99. [PMID: 23711909 DOI: 10.1016/j.ejpn.2013.04.010] [Citation(s) in RCA: 142] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/30/2012] [Revised: 02/28/2013] [Accepted: 04/28/2013] [Indexed: 11/16/2022]
Abstract
BACKGROUND AND OBJECTIVES Submicroscopic chromosomal rearrangements are the most common identifiable causes of intellectual disability and autism spectrum disorders associated with dysmorphic features. Chromosomal microarray (CMA) can detect copy number variants <1 Mb and identifies size and presence of known genes. The aim of this study was to demonstrate the usefulness of CMA, as a first-tier tool in detecting the etiology of unexplained intellectual disability/autism spectrum disorders (ID/ASDs) associated with dysmorphic features in a large cohort of pediatric patients. PATIENTS AND METHODS We studied 349 individuals; 223 males, 126 females, aged 5 months-19 years. Blood samples were analyzed with CMA at a resolution ranging from 1 Mb to 40 Kb. The imbalance was confirmed by FISH or qPCR. We considered copy number variants (CNVs) causative if the variant was responsible for a known syndrome, encompassed gene/s of known function, occurred de novo or, if inherited, the parent was variably affected, and/or the involved gene/s had been reported in association with ID/ASDs in dedicated databases. RESULTS 91 CNVs were detected in 77 (22.06%) patients: 5 (6.49%) of those presenting with borderline cognitive impairment, 54 (70.13%) with a variable degree of DD/ID, and 18/77 (23.38%) with ID of variable degree and ASDs. 16/77 (20.8%) patients had two different rearrangements. Deletions exceeded duplications (58 versus 33); 45.05% (41/91) of the detected CNVs were de novo, 45.05% (41/91) inherited, and 9.9% (9/91) unknown. The CNVs caused the phenotype in 57/77 (74%) patients; 12/57 (21.05%) had ASDs/ID, and 45/57 (78.95%) had DD/ID. CONCLUSIONS Our study provides further evidence of the high diagnostic yield of CMA for genetic testing in children with unexplained ID/ASDs who had dysmorphic features. We confirm the value of CMA as the first-tier tool in the assessment of those conditions in the pediatric setting.
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Affiliation(s)
- Agatino Battaglia
- Stella Maris Clinical Research Institute for Child and Adolescent Neuropsychiatry, via dei Giacinti, 2, 56128 Calambrone, Pisa, Italy.
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Zuo H, Chan GPW, Zhu J, Yeung WWS, Chan ASL, Ammer H, Wong YH. Activation state-dependent interaction between Gαq subunits and the Fhit tumor suppressor. Cell Commun Signal 2013; 11:59. [PMID: 23947369 PMCID: PMC3751744 DOI: 10.1186/1478-811x-11-59] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2013] [Accepted: 08/12/2013] [Indexed: 12/30/2022] Open
Abstract
Background The FHIT tumor suppressor gene is arguably the most commonly altered gene in cancer since it is inactivated in about 60% of human tumors. The Fhit protein is a member of the ubiquitous histidine triad proteins which hydrolyze dinucleoside polyphosphates such as Ap3A. Despite the fact that Fhit functions as a tumor suppressor, the pathway through which Fhit inhibits growth of cancer cells remains largely unknown. Phosphorylation by Src tyrosine kinases provides a linkage between Fhit and growth factor signaling. Since many G proteins can regulate cell proliferation through multiple signaling components including Src, we explored the relationship between Gα subunits and Fhit. Results Several members of the Gαq subfamily (Gα16, Gα14, and Gαq) were found to co-immunoprecipitate with Fhit in their GTP-bound active state in HEK293 cells. The binding of activated Gαq members to Fhit appeared to be direct and was detectable in native DLD-1 colon carcinoma cells. The use of Gα16/z chimeras further enabled the mapping of the Fhit-interacting domain to the α2-β4 region of Gα16. However, Gαq/Fhit did not affect either Ap3A binding and hydrolysis by Fhit, or the ability of Gαq/16 to regulate downstream effectors including phospholipase Cβ, Ras, ERK, STAT3, and IKK. Functional mutants of Fhit including the H96D, Y114F, L25W and L25W/I10W showed comparable abilities to associate with Gαq. Despite the lack of functional regulation of Gq signaling by Fhit, stimulation of Gq-coupled receptors in HEK293 and H1299 cells stably overexpressing Fhit led to reduced cell proliferation, as opposed to an enhanced cell proliferation typically seen with parental cells. Conclusions Activated Gαq members interact with Fhit through their α2-β4 region which may result in enhancement of the growth inhibitory effect of Fhit, thus providing a possible avenue for G protein-coupled receptors to modulate tumor suppression.
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Affiliation(s)
- Hao Zuo
- Division of Life Sciences, Biotechnology Research Institute, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
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Regulator of G protein signaling 19 suppresses Ras-induced neoplastic transformation and tumorigenesis. Cancer Lett 2013; 339:33-41. [PMID: 23911936 DOI: 10.1016/j.canlet.2013.07.025] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2013] [Revised: 07/12/2013] [Accepted: 07/24/2013] [Indexed: 11/20/2022]
Abstract
Regulator of G protein signaling 19 (RGS19) has recently been shown to inhibit Ras activation by upregulating the tumor metastasis suppressor Nm23. Here, we have examined the effect of RGS19 on Ras-induced oncogenesis. Coexpression of RGS19, but not RGS20, in NIH3T3 cells effectively suppressed neoplastic transformation and tumorigenesis induced by the oncogenic Ras(GV) mutant. In non-small cell lung carcinoma H1299 cells that harbor Ras mutations, shRNA-mediated knockdown of RGS19 facilitated tumorigenesis with the early appearance of large tumors in nude mice assays. Collectively, these results suggest that expression of RGS19 can suppress the oncogenic actions of Ras.
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RGS19 inhibits Ras signaling through Nm23H1/2-mediated phosphorylation of the kinase suppressor of Ras. Cell Signal 2013; 25:1064-74. [PMID: 23416464 DOI: 10.1016/j.cellsig.2013.02.010] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2013] [Accepted: 02/09/2013] [Indexed: 12/31/2022]
Abstract
Besides serving as signal terminators for G protein pathways, several regulators of G protein signaling (RGS) can also modulate cell proliferation. RGS19 has previously been shown to enhance Akt signaling despite impaired Ras signaling. The present study examines the mechanism by which RGS19 inhibits Ras signaling. In HEK293 cells stably expressing RGS19, serum-induced Ras activation and phosphorylations of Raf/MEK/ERK were significantly inhibited, while cells expressing RGS2, 4, 7, 8, 10, or 20 did not exhibit this inhibitory phenotype. Conversely, siRNA-mediated knockdown of RGS19 enabled partial recovery of serum-induced ERK phosphorylation. Interestingly, two isoforms of the tumor metastasis suppressor Nm23 (H1 and H2) were upregulated in 293/RGS19 cells. As a nucleoside diphosphate kinase, Nm23H1 can phosphorylate the kinase suppressor of Ras (KSR). Elevated levels of phosphorylated KSR were indeed detected in the nuclear fractions of 293/RGS19 cells. Co-immunoprecipitation assays revealed that Nm23H1/2 can form complexes with RGS19, Ras, or KSR. siRNA-mediated knockdown of Nm23H1/2 allowed 293/RGS19 cells to partially recover their ERK responses to serum treatment, while overexpression of Nm23H1/2 in HEK293 cells suppressed the serum-induced ERK response. This study demonstrates that expression of RGS19 can suppress Ras-mediated signaling via upregulation of Nm23.
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Kwan DHT, Yung LY, Ye RD, Wong YH. Activation of Ras-dependent signaling pathways by G(14) -coupled receptors requires the adaptor protein TPR1. J Cell Biochem 2013; 113:3486-97. [PMID: 22711498 DOI: 10.1002/jcb.24225] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Many G(q) -coupled receptors mediate mitogenic signals by stimulating extracellular signal-regulated protein kinases (ERKs) that are typically regulated by the small GTPase Ras. Recent studies have revealed that members of the Gα(q) family may possess the ability to activate Ras/ERK by interacting with the adaptor protein tetratricopeptide repeat 1 (TPR1). Within the Gα(q) family, the highly promiscuous Gα(14) can relay signals from numerous receptors. Here, we examined if Gα(14) interacts with TPR1 to stimulate Ras signaling pathways. Expression of the constitutively active Gα(14) QL mutant in HEK293 cells led to the formation of GTP-bound Ras as well as increased phosphorylations of downstream signaling molecules including ERK and IκB kinase. Stimulation of endogenous G(14) -coupled somatostatin type 2 and α(2) -adrenergic receptors produced similar responses in human hepatocellular HepG2 carcinoma cells. Co-immunoprecipitation assays using HEK293 cells demonstrated a stronger association of TPR1 for Gα(14) QL than Gα(14) , suggesting that TPR1 preferentially binds to the GTP-bound form of Gα(14) . Activated Gα(14) also interacted with the Ras guanine nucleotide exchange factors SOS1 and SOS2. Expression of a dominant negative mutant of TPR1 or siRNA-mediated knockdown of TPR1 effectively abolished the ability of Gα(14) to induce Ras signaling in native HepG2 or transfected HEK293 cells. Although expression of the dominant negative mutant of TPR1 suppressed Gα(14) QL-induced phosphorylations of ERK and IκB kinase, it did not affect Gα(14) QL-induced stimulation of phospholipase Cβ or c-Jun N-terminal kinase. Our results suggest that TPR1 is required for Gα(14) to stimulate Ras-dependent signaling pathways, but not for the propagation of signals along Ras-independent pathways.
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Affiliation(s)
- Dawna H T Kwan
- Division of Life Science and the Biotechnology Research Institute, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
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Lee MMK, Chui RKS, Tam IYS, Lau AHY, Wong YH. CCR1-mediated STAT3 tyrosine phosphorylation and CXCL8 expression in THP-1 macrophage-like cells involve pertussis toxin-insensitive Gα(14/16) signaling and IL-6 release. THE JOURNAL OF IMMUNOLOGY 2012; 189:5266-76. [PMID: 23125416 DOI: 10.4049/jimmunol.1103359] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Agonists of CCR1 contribute to hypersensitivity reactions and atherosclerotic lesions, possibly via the regulation of the transcription factor STAT3. CCR1 was demonstrated to use pertussis toxin-insensitive Gα(14/16) to stimulate phospholipase Cβ and NF-κB, whereas both Gα(14) and Gα(16) are also capable of activating STAT3. The coexpression of CCR1 and Gα(14/16) in human THP-1 macrophage-like cells suggests that CCR1 may use Gα(14/16) to induce STAT3 activation. In this study, we demonstrated that a CCR1 agonist, leukotactin-1 (CCL15), could indeed stimulate STAT3 Tyr(705) and Ser(727) phosphorylation via pertussis toxin-insensitive G proteins in PMA-differentiated THP-1 cells, human erythroleukemia cells, and HEK293 cells overexpressing CCR1 and Gα(14/16). The STAT3 Tyr(705) and Ser(727) phosphorylations were independent of each other and temporally distinct. Subcellular fractionation and confocal microscopy illustrated that Tyr(705)-phosphorylated STAT3 translocated to the nucleus, whereas Ser(727)-phosphorylated STAT3 was retained in the cytosol after CCR1/Gα(14) activation. CCL15 was capable of inducing IL-6 and IL-8 (CXCL8) production in both THP-1 macrophage-like cells and HEK293 cells overexpressing CCR1 and Gα(14/16). Neutralizing Ab to IL-6 inhibited CCL15-mediated STAT3 Tyr(705) phosphorylation, whereas inhibition of STAT3 activity abolished CCL15-activated CXCL8 release. The ability of CCR1 to signal through Gα(14/16) provides a linkage for CCL15 to regulate IL-6/STAT3-signaling cascades, leading to expression of CXCL8, a cytokine that is involved in inflammation and the rupture of atherosclerotic plaque.
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Affiliation(s)
- Maggie M K Lee
- Division of Life Science, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
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Ip AKC, Tso PH, Lee MMK, Wong YH. Elevated expression of RGS19 impairs the responsiveness of stress-activated protein kinases to serum. Mol Cell Biochem 2011; 362:159-68. [PMID: 22045062 DOI: 10.1007/s11010-011-1138-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2011] [Accepted: 10/22/2011] [Indexed: 12/17/2022]
Abstract
Regulators of G protein signaling (RGS proteins) serve as GTPase activating proteins for the signal transducing Gα subunits. RGS19, also known as Gα-interacting protein (GAIP), has been shown to subserve other functions such as the regulation of macroautophagy and growth factor signaling. We have recently demonstrated that the expression of RGS19 in human embryonic kidney (HEK) 293 cells resulted in the disruption of serum-induced mitogenic response along the classical Ras/Raf/MEK/ERK pathway. Here, we further examined the effect of RGS19 expression on the stress-activated protein kinases (SAPKs). Both c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK) became non-responsive to serum in 293/RGS19 cells, yet the two SAPKs responded to UV irradiation or osmotic stress induced by sorbitol. Kinases upstream of JNK and p38 MAPK, including MKK3/6, MKK4, and MLK3, also failed to respond to serum stimulation in 293/RGS19 cells. Serum-induced activation of the small GTPases Rac1 and Cdc42 was similarly suppressed in these cells. Our results indicate that elevated expression of RGS19 can severely disrupt the regulation of MAPKs by small GTPases.
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Affiliation(s)
- Angel K C Ip
- Division of Life Science and the Biotechnology Research Institute, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
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14
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Yoo JK, Kim J, Choi SJ, Kim CH, Lee DR, Chung HM, Kim JK. The hsa-miR-5739 modulates the endoglin network in endothelial cells derived from human embryonic stem cells. Biochem Biophys Res Commun 2011; 415:258-62. [DOI: 10.1016/j.bbrc.2011.10.030] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2011] [Accepted: 10/07/2011] [Indexed: 12/29/2022]
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15
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RGS19 stimulates cell proliferation by deregulating cell cycle control and enhancing Akt signaling. Cancer Lett 2011; 309:199-208. [DOI: 10.1016/j.canlet.2011.06.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2011] [Revised: 05/09/2011] [Accepted: 06/01/2011] [Indexed: 11/13/2022]
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16
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Liu AM, Lo RK, Guo EX, Ho MK, Ye RD, Wong YH. Gα16 interacts with tetratricopeptide repeat 1 (TPR1) through its β3 region to activate Ras independently of phospholipase Cβ signaling. BMC STRUCTURAL BIOLOGY 2011; 11:17. [PMID: 21486497 PMCID: PMC3098143 DOI: 10.1186/1472-6807-11-17] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/06/2010] [Accepted: 04/13/2011] [Indexed: 12/02/2022]
Abstract
Background G protein-coupled receptors constitute the largest family of cell surface receptors in the mammalian genome. As the core of the G protein signal transduction machinery, the Gα subunits are required to interact with multiple partners. The GTP-bound active state of many Gα subunits can bind a multitude of effectors and regulatory proteins. Yet it remains unclear if the different proteins utilize distinct or common structural motifs on the Gα subunit for binding. Using Gα16 as a model, we asked if its recently discovered adaptor protein tetratricopeptide repeat 1 (TPR1) binds to the same region as its canonical effector, phospholipase Cβ (PLCβ). Results We have examined the specificity of Gα16/TPR1 association by testing a series of chimeras between Gα16 and Gαz. TPR1 co-immunoprecipitated with Gα16 and more tightly with its constitutively active Gα16QL, but not Gαz. Progressive replacement of Gα16 sequence with the corresponding residues of Gαz eventually identified a stretch of six amino acids in the β3 region of Gα16 which are responsible for TPR1 interaction and the subsequent Ras activation. Insertion of these six residues into Gαz allowed productive TPR1-interaction. Since the β3 region only minimally contributes to interact with PLCβ, several chimeras exhibited differential abilities to stimulate PLCβ and Ras. The ability of the chimeras to activate downstream transcription factors such as signal transducer and activator of transcription 3 and nuclear factor κB appeared to be associated with PLCβ signaling. Conclusions Our results suggest that Gα16 can signal through TPR1/Ras and PLCβ simultaneously and independently. The β3 region of Gα16 is essential for interaction with TPR1 and the subsequent activation of Ras, but has relatively minor influence on the PLCβ interaction. Gα16 may utilize different structural domains to bind TPR1 and PLCβ.
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Affiliation(s)
- Andrew Mf Liu
- Division of Life Science and the Biotechnology Research Institute, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
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