1
|
Ngo VA. Insight into molecular basis and dynamics of full-length CRaf kinase in cellular signaling mechanisms. Biophys J 2024:S0006-3495(24)00438-7. [PMID: 38946141 DOI: 10.1016/j.bpj.2024.06.028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2024] [Revised: 05/15/2024] [Accepted: 06/28/2024] [Indexed: 07/02/2024] Open
Abstract
Raf kinases play key roles in signal transduction in cells for regulating proliferation, differentiation, and survival. Despite decades of research into functions and dynamics of Raf kinases with respect to other cytosolic proteins, understanding Raf kinases is limited by the lack of their full-length structures at the atomic resolution. Here, we present the first model of the full-length CRaf kinase obtained from artificial intelligence/machine learning algorithms with a converging ensemble of structures simulated by large-scale temperature replica exchange simulations. Our model is validated by comparing simulated structures with the latest cryo-EM structure detailing close contacts among three key domains and regions of the CRaf. Our simulations identify potentially new epitopes of intramolecule interactions within the CRaf and reveal a dynamical nature of CRaf kinases, in which the three domains can move back and forth relative to each other for regulatory dynamics. The dynamic conformations are then used in a docking algorithm to shed insight into the paradoxical effect caused by vemurafenib in comparison with a paradox breaker PLX7904. We propose a model of Raf-heterodimer/KRas-dimer as a signalosome based on the dynamics of the full-length CRaf.
Collapse
Affiliation(s)
- Van A Ngo
- Advanced Computing for Life Sciences and Engineering, Science Engagement Section, Computing and Computational Sciences, National Center for Computational Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee.
| |
Collapse
|
2
|
Cooke SF, Wright TA, Sin YY, Ling J, Kyurkchieva E, Phanthaphol N, Mcskimming T, Herbert K, Rebus S, Biankin AV, Chang DK, Baillie GS, Blair CM. Disruption of the pro-oncogenic c-RAF-PDE8A complex represents a differentiated approach to treating KRAS-c-RAF dependent PDAC. Sci Rep 2024; 14:8998. [PMID: 38637546 PMCID: PMC11026450 DOI: 10.1038/s41598-024-59451-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Accepted: 04/10/2024] [Indexed: 04/20/2024] Open
Abstract
Pancreatic ductal adenocarcinoma (PDAC) is considered the third leading cause of cancer mortality in the western world, offering advanced stage patients with few viable treatment options. Consequently, there remains an urgent unmet need to develop novel therapeutic strategies that can effectively inhibit pro-oncogenic molecular targets underpinning PDACs pathogenesis and progression. One such target is c-RAF, a downstream effector of RAS that is considered essential for the oncogenic growth and survival of mutant RAS-driven cancers (including KRASMT PDAC). Herein, we demonstrate how a novel cell-penetrating peptide disruptor (DRx-170) of the c-RAF-PDE8A protein-protein interaction (PPI) represents a differentiated approach to exploiting the c-RAF-cAMP/PKA signaling axes and treating KRAS-c-RAF dependent PDAC. Through disrupting the c-RAF-PDE8A protein complex, DRx-170 promotes the inactivation of c-RAF through an allosteric mechanism, dependent upon inactivating PKA phosphorylation. DRx-170 inhibits cell proliferation, adhesion and migration of a KRASMT PDAC cell line (PANC1), independent of ERK1/2 activity. Moreover, combining DRx-170 with afatinib significantly enhances PANC1 growth inhibition in both 2D and 3D cellular models. DRx-170 sensitivity appears to correlate with c-RAF dependency. This proof-of-concept study supports the development of DRx-170 as a novel and differentiated strategy for targeting c-RAF activity in KRAS-c-RAF dependent PDAC.
Collapse
Affiliation(s)
- Sean F Cooke
- College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, Scotland, UK
| | - Thomas A Wright
- College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, Scotland, UK
| | - Yuan Yan Sin
- College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, Scotland, UK
| | - Jiayue Ling
- College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, Scotland, UK
| | - Elka Kyurkchieva
- College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, Scotland, UK
| | - Nattaporn Phanthaphol
- Siriraj Centre of Research Excellence for Cancer Immunotherapy, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand
| | - Thomas Mcskimming
- College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, Scotland, UK
| | - Katharine Herbert
- Wolfson Wohl Cancer Research Centre, Institute of Cancer Sciences, University of Glasgow, Glasgow, Scotland, UK
| | - Selma Rebus
- Wolfson Wohl Cancer Research Centre, Institute of Cancer Sciences, University of Glasgow, Glasgow, Scotland, UK
| | - Andrew V Biankin
- Wolfson Wohl Cancer Research Centre, Institute of Cancer Sciences, University of Glasgow, Glasgow, Scotland, UK
| | - David K Chang
- Wolfson Wohl Cancer Research Centre, Institute of Cancer Sciences, University of Glasgow, Glasgow, Scotland, UK
| | - George S Baillie
- College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, Scotland, UK
| | - Connor M Blair
- College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, Scotland, UK.
| |
Collapse
|
3
|
Sears JC, Broadie K. Use-Dependent, Untapped Dual Kinase Signaling Localized in Brain Learning Circuitry. J Neurosci 2024; 44:e1126232024. [PMID: 38267256 PMCID: PMC10957217 DOI: 10.1523/jneurosci.1126-23.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Revised: 01/12/2024] [Accepted: 01/16/2024] [Indexed: 01/26/2024] Open
Abstract
Imaging brain learning and memory circuit kinase signaling is a monumental challenge. The separation of phases-based activity reporter of kinase (SPARK) biosensors allow circuit-localized studies of multiple interactive kinases in vivo, including protein kinase A (PKA) and extracellular signal-regulated kinase (ERK) signaling. In the precisely-mapped Drosophila brain learning/memory circuit, we find PKA and ERK signaling differentially enriched in distinct Kenyon cell connectivity nodes. We discover that potentiating normal circuit activity induces circuit-localized PKA and ERK signaling, expanding kinase function within new presynaptic and postsynaptic domains. Activity-induced PKA signaling shows extensive overlap with previously selective ERK signaling nodes, while activity-induced ERK signaling arises in new connectivity nodes. We find targeted synaptic transmission blockade in Kenyon cells elevates circuit-localized ERK induction in Kenyon cells with normally high baseline ERK signaling, suggesting lateral and feedback inhibition. We discover overexpression of the pathway-linking Meng-Po (human SBK1) serine/threonine kinase to improve learning acquisition and memory consolidation results in dramatically heightened PKA and ERK signaling in separable Kenyon cell circuit connectivity nodes, revealing both synchronized and untapped signaling potential. Finally, we find that a mechanically-induced epileptic seizure model (easily shocked "bang-sensitive" mutants) has strongly elevated, circuit-localized PKA and ERK signaling. Both sexes were used in all experiments, except for the hemizygous male-only seizure model. Hyperexcitable, learning-enhanced, and epileptic seizure models have comparably elevated interactive kinase signaling, suggesting a common basis of use-dependent induction. We conclude that PKA and ERK signaling modulation is locally coordinated in use-dependent spatial circuit dynamics underlying seizure susceptibility linked to learning/memory potential.
Collapse
Affiliation(s)
- James C Sears
- Vanderbilt Brain Institute, Vanderbilt University and Medical Center, Nashville, Tennessee 37235
- Departments of Biological Sciences, Vanderbilt University and Medical Center, Nashville, Tennessee 37235
| | - Kendal Broadie
- Vanderbilt Brain Institute, Vanderbilt University and Medical Center, Nashville, Tennessee 37235
- Departments of Biological Sciences, Vanderbilt University and Medical Center, Nashville, Tennessee 37235
- Cell and Developmental Biology, Vanderbilt University and Medical Center, Nashville, Tennessee 37235
- Vanderbilt Kennedy Center, Vanderbilt University and Medical Center, Nashville, Tennessee 37235
| |
Collapse
|
4
|
Glycosphingolipids are mediators of cancer plasticity through independent signaling pathways. Cell Rep 2022; 40:111181. [PMID: 35977490 DOI: 10.1016/j.celrep.2022.111181] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Revised: 06/01/2022] [Accepted: 07/19/2022] [Indexed: 11/23/2022] Open
Abstract
The molecular repertoire promoting cancer cell plasticity is not fully elucidated. Here, we propose that glycosphingolipids (GSLs), specifically the globo and ganglio series, correlate and promote the transition between epithelial and mesenchymal cells. The epithelial character of ovarian cancer remains stable throughout disease progression, and spatial glycosphingolipidomics reveals elevated globosides in the tumor compartment compared with the ganglioside-rich stroma. CRISPR-Cas9 knockin mediated truncation of endogenous E-cadherin induces epithelial-to-mesenchymal transition (EMT) and decreases globosides. The transcriptomics analysis identifies the ganglioside-synthesizing enzyme ST8SIA1 to be consistently elevated in mesenchymal-like samples, predicting poor outcome. Subsequent deletion of ST8SIA1 induces epithelial cell features through mTORS2448 phosphorylation, whereas loss of globosides in ΔA4GALT cells, resulting in EMT, is accompanied by increased ERKY202/T204 and AKTS124. The GSL composition dynamics corroborate cancer cell plasticity, and further evidence suggests that mesenchymal cells are maintained through ganglioside-dependent, calcium-mediated mechanisms.
Collapse
|
5
|
Zhao J, Luo Z. Discovery of Raf Family Is a Milestone in Deciphering the Ras-Mediated Intracellular Signaling Pathway. Int J Mol Sci 2022; 23:ijms23095158. [PMID: 35563547 PMCID: PMC9101324 DOI: 10.3390/ijms23095158] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Revised: 05/02/2022] [Accepted: 05/03/2022] [Indexed: 01/27/2023] Open
Abstract
The Ras-Raf-MEK-ERK signaling pathway, the first well-established MAPK pathway, plays essential roles in cell proliferation, survival, differentiation and development. It is activated in over 40% of human cancers owing to mutations of Ras, membrane receptor tyrosine kinases and other oncogenes. The Raf family consists of three isoforms, A-Raf, B-Raf and C-Raf. Since the first discovery of a truncated mutant of C-Raf as a transforming oncogene carried by a murine retrovirus, forty years of extensive studies have provided a wealth of information on the mechanisms underlying the activation, regulation and biological functions of the Raf family. However, the mechanisms by which activation of A-Raf and C-Raf is accomplished are still not completely understood. In contrast, B-Raf can be easily activated by binding of Ras-GTP, followed by cis-autophosphorylation of the activation loop, which accounts for the fact that this isoform is frequently mutated in many cancers, especially melanoma. The identification of oncogenic B-Raf mutations has led to accelerated drug development that targets Raf signaling in cancer. However, the effort has not proved as effective as anticipated, inasmuch as the mechanism of Raf activation involves multiple steps, factors and phosphorylation of different sites, as well as complex interactions between Raf isoforms. In this review, we will focus on the physiological complexity of the regulation of Raf kinases and their connection to the ERK phosphorylation cascade and then discuss the role of Raf in tumorigenesis and the clinical application of Raf inhibitors in the treatment of cancer.
Collapse
Affiliation(s)
- Jingtong Zhao
- Queen Mary School, Nanchang University, Nanchang 330031, China;
| | - Zhijun Luo
- Queen Mary School, Nanchang University, Nanchang 330031, China;
- Provincial Key Laboratory of Tumor Pathogens and Molecular Pathology, Nanchang University, Nanchang 330031, China
- NCU-QMUL Joint Research Institute of Precision Medical Science, Nanchang 330031, China
- Correspondence:
| |
Collapse
|
6
|
PDE4D targeting enhances anti-tumor effects of sorafenib in clear cell renal cell carcinoma and attenuates MAPK/ERK signaling in a CRAF-dependent manner. Transl Oncol 2022; 19:101377. [PMID: 35196602 PMCID: PMC8866901 DOI: 10.1016/j.tranon.2022.101377] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Accepted: 02/15/2022] [Indexed: 01/16/2023] Open
|
7
|
Quantitative live-cell imaging of GPCR downstream signaling dynamics. Biochem J 2022; 479:883-900. [PMID: 35383830 DOI: 10.1042/bcj20220021] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Revised: 04/03/2022] [Accepted: 04/06/2022] [Indexed: 11/17/2022]
Abstract
G-protein-coupled receptors (GPCRs) play an important role in sensing various extracellular stimuli, such as neurotransmitters, hormones, and tastants, and transducing the input information into the cell. While the human genome encodes more than 800 GPCR genes, only four Gα-proteins (Gαs, Gαi/o, Gαq/11, and Gα12/13) are known to couple with GPCRs. It remains unclear how such divergent GPCR information is translated into the downstream G-protein signaling dynamics. To answer this question, we report a live-cell fluorescence imaging system for monitoring GPCR downstream signaling dynamics. Genetically encoded biosensors for cAMP, Ca2+, RhoA, and ERK were selected as markers for GPCR downstream signaling, and were stably expressed in HeLa cells. GPCR was further transiently overexpressed in the cells. As a proof-of-concept, we visualized GPCR signaling dynamics of 5 dopamine receptors and 12 serotonin receptors, and found heterogeneity between GPCRs and between cells. Even when the same Gα proteins were known to be coupled, the patterns of dynamics in GPCR downstream signaling, including the signal strength and duration, were substantially distinct among GPCRs. These results suggest the importance of dynamical encoding in GPCR signaling.
Collapse
|
8
|
Zhang P, Huang Y, Fu Q, He W, Xiao K, Zhang M. Integrated analysis of phosphoproteome and ubiquitylome in epididymal sperm of buffalo (Bubalus bubalis). Mol Reprod Dev 2021; 88:15-33. [PMID: 33140506 PMCID: PMC7894524 DOI: 10.1002/mrd.23432] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Revised: 09/14/2020] [Accepted: 10/13/2020] [Indexed: 12/20/2022]
Abstract
In mammals, sperm need to mature in the epididymis to gain fertilization competency. However, the molecular mechanism underlying buffalo sperm maturation remains elusive. Exploring sperm physiology at the posttranslational modification (PTM) level could help to develop our understanding of these mechanisms. Protein phosphorylation and ubiquitination are major PTMs in the regulation of many biological processes. In the present study, to our knowledge, we report the first phosphoproteome and ubiquitylome of sperm collected from the caput, corpus, and cauda segments of the epididymis using liquid chromatography-mass spectrometry combined with affinity purification. In total, 647 phosphorylation sites in 294 proteins and 1063 ubiquitination sites in 446 proteins were characterized. Some of these proteins were associated with cellular developmental processes and energy metabolic pathways. Interestingly, 84 proteins were both phosphorylated and ubiquitinated, simultaneously. Some of these proteins were involved in, for example, spermatogenesis, reproduction, and spermatid development. Taken together, these data provide a theoretical basis for further functional analysis of phosphorylation and ubiquitination in epididymal sperm of buffalo and other mammals, and serve as an important resource for exploring the physiological mechanism underlying sperm maturation.
Collapse
Affiliation(s)
- Peng‐fei Zhang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro‐Bioresources, Animal Reproduction InstituteGuangxi UniversityNanningGuangxiChina
| | - Yu‐lin Huang
- Department of Cell and Genetics, College of Basic MedicineGuangxi University of Chinese MedicineNanningGuangxiChina
| | - Qiang Fu
- State Key Laboratory for Conservation and Utilization of Subtropical Agro‐Bioresources, Animal Reproduction InstituteGuangxi UniversityNanningGuangxiChina
| | - Weng‐tan He
- State Key Laboratory for Conservation and Utilization of Subtropical Agro‐Bioresources, Animal Reproduction InstituteGuangxi UniversityNanningGuangxiChina
| | - Kai Xiao
- State Key Laboratory for Conservation and Utilization of Subtropical Agro‐Bioresources, Animal Reproduction InstituteGuangxi UniversityNanningGuangxiChina
| | - Ming Zhang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro‐Bioresources, Animal Reproduction InstituteGuangxi UniversityNanningGuangxiChina
| |
Collapse
|
9
|
Yuan J, Dong X, Yap J, Hu J. The MAPK and AMPK signalings: interplay and implication in targeted cancer therapy. J Hematol Oncol 2020; 13:113. [PMID: 32807225 PMCID: PMC7433213 DOI: 10.1186/s13045-020-00949-4] [Citation(s) in RCA: 240] [Impact Index Per Article: 60.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Accepted: 08/04/2020] [Indexed: 02/06/2023] Open
Abstract
Cancer is characterized as a complex disease caused by coordinated alterations of multiple signaling pathways. The Ras/RAF/MEK/ERK (MAPK) signaling is one of the best-defined pathways in cancer biology, and its hyperactivation is responsible for over 40% human cancer cases. To drive carcinogenesis, this signaling promotes cellular overgrowth by turning on proliferative genes, and simultaneously enables cells to overcome metabolic stress by inhibiting AMPK signaling, a key singular node of cellular metabolism. Recent studies have shown that AMPK signaling can also reversibly regulate hyperactive MAPK signaling in cancer cells by phosphorylating its key components, RAF/KSR family kinases, which affects not only carcinogenesis but also the outcomes of targeted cancer therapies against the MAPK signaling. In this review, we will summarize the current proceedings of how MAPK-AMPK signalings interplay with each other in cancer biology, as well as its implications in clinic cancer treatment with MAPK inhibition and AMPK modulators, and discuss the exploitation of combinatory therapies targeting both MAPK and AMPK as a novel therapeutic intervention.
Collapse
Affiliation(s)
- Jimin Yuan
- Department of Urology, Shenzhen People's Hospital (The Second Clinical Medical College, Jinan University; The First Affiliated Hospital, Southern University of Science and Technology), Shenzhen, 518020, Guangdong, China.
- Geriatric Department, Shenzhen People's Hospital (The Second Clinical Medical College, Jinan University; The First Affiliated Hospital, Southern University of Science and Technology), Shenzhen, 518020, Guangdong, China.
| | - Xiaoduo Dong
- Shenzhen People's Hospital, 1017 Dongmen North Road, Shenzhen, 518020, China
| | - Jiajun Yap
- Cancer and Stem Cell Program, Duke-NUS Medical School, 8 College Road, Singapore, 169857, Singapore
| | - Jiancheng Hu
- Cancer and Stem Cell Program, Duke-NUS Medical School, 8 College Road, Singapore, 169857, Singapore.
- Division of Cellular and Molecular Research, National Cancer Centre Singapore, 11 Hospital Drive, Singapore, 169610, Singapore.
| |
Collapse
|
10
|
Degirmenci U, Wang M, Hu J. Targeting Aberrant RAS/RAF/MEK/ERK Signaling for Cancer Therapy. Cells 2020; 9:E198. [PMID: 31941155 PMCID: PMC7017232 DOI: 10.3390/cells9010198] [Citation(s) in RCA: 295] [Impact Index Per Article: 73.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Revised: 12/29/2019] [Accepted: 01/10/2020] [Indexed: 12/13/2022] Open
Abstract
The RAS/RAF/MEK/ERK (MAPK) signaling cascade is essential for cell inter- and intra-cellular communication, which regulates fundamental cell functions such as growth, survival, and differentiation. The MAPK pathway also integrates signals from complex intracellular networks in performing cellular functions. Despite the initial discovery of the core elements of the MAPK pathways nearly four decades ago, additional findings continue to make a thorough understanding of the molecular mechanisms involved in the regulation of this pathway challenging. Considerable effort has been focused on the regulation of RAF, especially after the discovery of drug resistance and paradoxical activation upon inhibitor binding to the kinase. RAF activity is regulated by phosphorylation and conformation-dependent regulation, including auto-inhibition and dimerization. In this review, we summarize the recent major findings in the study of the RAS/RAF/MEK/ERK signaling cascade, particularly with respect to the impact on clinical cancer therapy.
Collapse
Affiliation(s)
- Ufuk Degirmenci
- Division of Cellular and Molecular Research, National Cancer Centre Singapore, 11 Hospital Crescent, Singapore 169610, Singapore
| | - Mei Wang
- Cancer and Stem Cell Biology Program, Duke-NUS Medical School, 8 College Road, Singapore 169857, Singapore
| | - Jiancheng Hu
- Division of Cellular and Molecular Research, National Cancer Centre Singapore, 11 Hospital Crescent, Singapore 169610, Singapore
- Cancer and Stem Cell Biology Program, Duke-NUS Medical School, 8 College Road, Singapore 169857, Singapore
| |
Collapse
|
11
|
In-cell single-molecule FRET measurements reveal three conformational state changes in RAF protein. Biochim Biophys Acta Gen Subj 2019; 1864:129358. [PMID: 31071411 DOI: 10.1016/j.bbagen.2019.04.022] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2018] [Revised: 04/26/2019] [Accepted: 04/30/2019] [Indexed: 12/19/2022]
Abstract
BACKGROUND The structures of proteins are intimately related to their functions. Significant efforts have been dedicated to the structural investigation of proteins, mainly those of purified proteins in in vitro environments. Proteins function in living cells and thus protein structures must be regulated by interactions with various molecules, some of which participate in reaction networks, depending on the states, conditions, or actions of the cell. Therefore, it is very important to understand the structural behavior of proteins in living cells. METHODS Single-molecule Förster resonance energy transfer (smFRET) measurements were conducted using the alternative laser excitation (ALEX) technique. smFRET distributions of cytosolic Rapidly Accelerated Fibrosarcoma (RAF) proteins in living HeLa cells were obtained with exclusion of the negative effects of photobleached fluorophores and incompletely labeled proteins on smFRET. RESULTS smFRET histograms of wildtype (wt) RAF in live cells exhibited two major peaks, whereas that of the S621A mutant, which has been thought to have an expanded structure, was almost single-peaked. A population shift involving the peaks for wt RAF was detected upon epidermal growth factor stimulation. Spontaneous transitions between the conformational states corresponding to the two peaks were also detected using the FRET-two-channel kernel-based density distribution estimator method in comparison to static double-stranded DNA samples. CONCLUSIONS Cytosolic CRAF has at least three conformational states; in addition to the closed and open forms, the fully-open form was distinctly specified. Based on the results, we propose a speculative structural model for CRAF. GENERAL SIGNIFICANCE Structural distribution and changes to proteins in live cells as a result of intracellular interactions were successfully identified. smFRET using ALEX is applicable to any other cytosolic proteins.
Collapse
|
12
|
Wang Y, Hoermann B, Pavic K, Trebacz M, Rios P, Köhn M. Interrogating PP1 Activity in the MAPK Pathway with Optimized PP1-Disrupting Peptides. Chembiochem 2018; 20:66-71. [PMID: 30338897 PMCID: PMC6471087 DOI: 10.1002/cbic.201800541] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2018] [Indexed: 12/22/2022]
Abstract
Protein phosphatase‐1 (PP1)‐disrupting peptides (PDPs) are selective chemical modulators of PP1 that liberate the active PP1 catalytic subunit from regulatory proteins; thus allowing the dephosphorylation of nearby substrates. We have optimized the original cell‐active PDP3 for enhanced stability, and obtained insights into the chemical requirements for stabilizing this 23‐mer peptide for cellular applications. The optimized PDP‐Nal was used to dissect the involvement of PP1 in the MAPK signaling cascade. Specifically, we have demonstrated that, in human osteosarcoma (U2OS) cells, phosphoMEK1/2 is a direct substrate of PP1, whereas dephosphorylation of phosphoERK1/2 is indirect and likely mediated through enhanced tyrosine phosphatase activity after PDP‐mediated PP1 activation. Thus, as liberators of PP1 activity, PDPs represent a valuable tool for identifying the substrates of PP1 and understanding its role in diverse signaling cascades.
Collapse
Affiliation(s)
- Yansong Wang
- Genome Biology Unit, European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117, Heidelberg, Germany
| | - Bernhard Hoermann
- Genome Biology Unit, European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117, Heidelberg, Germany.,Faculty of Biology and BIOSS-Centre for Biological Signalling Studies, Albert-Ludwigs-University of Freiburg, Schänzlestrasse 18, 79104, Freiburg, Germany.,Collaboration for joint PhD degree between EMBL and, Heidelberg University, Faculty of Biosciences, Heidelberg, Germany
| | - Karolina Pavic
- Genome Biology Unit, European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117, Heidelberg, Germany
| | - Malgorzata Trebacz
- Faculty of Biology and BIOSS-Centre for Biological Signalling Studies, Albert-Ludwigs-University of Freiburg, Schänzlestrasse 18, 79104, Freiburg, Germany
| | - Pablo Rios
- Faculty of Biology and BIOSS-Centre for Biological Signalling Studies, Albert-Ludwigs-University of Freiburg, Schänzlestrasse 18, 79104, Freiburg, Germany
| | - Maja Köhn
- Genome Biology Unit, European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117, Heidelberg, Germany.,Faculty of Biology and BIOSS-Centre for Biological Signalling Studies, Albert-Ludwigs-University of Freiburg, Schänzlestrasse 18, 79104, Freiburg, Germany
| |
Collapse
|
13
|
Yuan J, Ng WH, Yap J, Chia B, Huang X, Wang M, Hu J. The AMPK inhibitor overcomes the paradoxical effect of RAF inhibitors through blocking phospho-Ser-621 in the C terminus of CRAF. J Biol Chem 2018; 293:14276-14284. [PMID: 30030377 PMCID: PMC6139560 DOI: 10.1074/jbc.ra118.004597] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Revised: 07/17/2018] [Indexed: 11/15/2022] Open
Abstract
The dimerization-driven paradoxical activation of RAF proto-oncogene Ser/Thr kinase (RAF) is the predominant cause of drug resistance and toxicity in cancer therapies with RAF inhibitors. The scaffold protein 14-3-3, which binds to the RAF C terminus, is essential for RAF activation under physiological conditions, but the molecular basis is unclear. Here we investigated whether and how 14-3-3 regulates the dimerization-driven transactivation of the RAF isoform CRAF by RAF inhibitors and affects drug resistance and toxicity by virtue of the dominant role of CRAF in these processes. We demonstrated that 14-3-3 enhances the dimerization-driven transactivation of CRAF by stabilizing CRAF dimers. Further, we identified AMP-activated protein kinase (AMPK) and CRAF itself as two putative kinases that redundantly phosphorylate CRAF's C terminus and thereby control its association with 14-3-3. Next, we determined whether the combinatory inhibition of AMPK and CRAF could overcome the paradoxical effect of RAF inhibitors. We found that the AMPK inhibitor (AMPKi) not only blocked the RAF inhibitor–driven paradoxical activation of ERK signaling and cellular overgrowth in Ras-mutated cancer cells by blocking phosphorylation of Ser-621 in CRAF but also reduced the formation of drug-resistant clones of BRAFV600E-mutated cancer cells. Last, we investigated whether 14-3-3 binding to the C terminus of CRAF is required for CRAF catalytic activity and observed that it was dispensable in vivo. Altogether, our study unravels the molecular mechanism by which 14-3-3 regulates dimerization-driven RAF activation and identified AMPKi as a potential agent to counteract drug resistance and adverse effects of RAF inhibitors in cancer therapies.
Collapse
Affiliation(s)
- Jimin Yuan
- From the Division of Cellular and Molecular Research, National Cancer Centre Singapore, 11 Hospital Drive, Singapore 169610, Singapore and
| | - Wan Hwa Ng
- From the Division of Cellular and Molecular Research, National Cancer Centre Singapore, 11 Hospital Drive, Singapore 169610, Singapore and
| | - Jiajun Yap
- From the Division of Cellular and Molecular Research, National Cancer Centre Singapore, 11 Hospital Drive, Singapore 169610, Singapore and
| | - Brandon Chia
- From the Division of Cellular and Molecular Research, National Cancer Centre Singapore, 11 Hospital Drive, Singapore 169610, Singapore and
| | - Xuchao Huang
- From the Division of Cellular and Molecular Research, National Cancer Centre Singapore, 11 Hospital Drive, Singapore 169610, Singapore and
| | - Mei Wang
- the Cancer and Stem Cell Program, Duke-NUS Medical School, 8 College Road, Singapore 169857, Singapore
| | - Jiancheng Hu
- From the Division of Cellular and Molecular Research, National Cancer Centre Singapore, 11 Hospital Drive, Singapore 169610, Singapore and .,the Cancer and Stem Cell Program, Duke-NUS Medical School, 8 College Road, Singapore 169857, Singapore
| |
Collapse
|
14
|
Mohl BP, Emmott E, Roy P. Phosphoproteomic Analysis Reveals the Importance of Kinase Regulation During Orbivirus Infection. Mol Cell Proteomics 2017; 16:1990-2005. [PMID: 28851738 PMCID: PMC5672004 DOI: 10.1074/mcp.m117.067355] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Revised: 08/08/2017] [Indexed: 01/03/2023] Open
Abstract
Bluetongue virus (BTV) causes infections in wild and domesticated ruminants with high morbidity and mortality and is responsible for significant economic losses in both developing and developed countries. BTV serves as a model for the study of other members of the Orbivirus genus. Previously, the importance of casein kinase 2 for BTV replication was demonstrated. To identify intracellular signaling pathways and novel host-cell kinases involved during BTV infection, the phosphoproteome of BTV infected cells was analyzed. Over 1000 phosphosites were identified using mass spectrometry, which were then used to determine the corresponding kinases involved during BTV infection. This analysis yielded protein kinase A (PKA) as a novel kinase activated during BTV infection. Subsequently, the importance of PKA for BTV infection was validated using a PKA inhibitor and activator. Our data confirmed that PKA was essential for efficient viral growth. Further, we showed that PKA is also required for infection of equid cells by African horse sickness virus, another member of the Orbivirus genus. Thus, despite their preference in specific host species, orbiviruses may utilize the same host signaling pathways during their replication.
Collapse
Affiliation(s)
- Bjorn-Patrick Mohl
- From the ‡Department of Pathogen Molecular Biology, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK
| | - Edward Emmott
- §University of Cambridge, Division of Virology, Department of Pathology, Lab block level 5, Box 237, Addenbrookes Hospital, Cambridge, UK
| | - Polly Roy
- From the ‡Department of Pathogen Molecular Biology, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK;
| |
Collapse
|
15
|
78495111110.3390/cancers9050052" />
Abstract
The epidermal growth factor receptor (EGFR) is a receptor tyrosine kinase that is commonly upregulated in cancers such as in non-small-cell lung cancer, metastatic colorectal cancer, glioblastoma, head and neck cancer, pancreatic cancer, and breast cancer. Various mechanisms mediate the upregulation of EGFR activity, including common mutations and truncations to its extracellular domain, such as in the EGFRvIII truncations, as well as to its kinase domain, such as the L858R and T790M mutations, or the exon 19 truncation. These EGFR aberrations over-activate downstream pro-oncogenic signaling pathways, including the RAS-RAF-MEK-ERK MAPK and AKT-PI3K-mTOR pathways. These pathways then activate many biological outputs that are beneficial to cancer cell proliferation, including their chronic initiation and progression through the cell cycle. Here, we review the molecular mechanisms that regulate EGFR signal transduction, including the EGFR structure and its mutations, ligand binding and EGFR dimerization, as well as the signaling pathways that lead to G1 cell cycle progression. We focus on the induction of CYCLIN D expression, CDK4/6 activation, and the repression of cyclin-dependent kinase inhibitor proteins (CDKi) by EGFR signaling pathways. We also discuss the successes and challenges of EGFR-targeted therapies, and the potential for their use in combination with CDK4/6 inhibitors.
Collapse
|
16
|
Wee P, Wang Z. Epidermal Growth Factor Receptor Cell Proliferation Signaling Pathways. Cancers (Basel) 2017; 9:cancers9050052. [PMID: 28513565 PMCID: PMC5447962 DOI: 10.3390/cancers9050052] [Citation(s) in RCA: 994] [Impact Index Per Article: 142.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Revised: 05/10/2017] [Accepted: 05/10/2017] [Indexed: 12/12/2022] Open
Abstract
The epidermal growth factor receptor (EGFR) is a receptor tyrosine kinase that is commonly upregulated in cancers such as in non-small-cell lung cancer, metastatic colorectal cancer, glioblastoma, head and neck cancer, pancreatic cancer, and breast cancer. Various mechanisms mediate the upregulation of EGFR activity, including common mutations and truncations to its extracellular domain, such as in the EGFRvIII truncations, as well as to its kinase domain, such as the L858R and T790M mutations, or the exon 19 truncation. These EGFR aberrations over-activate downstream pro-oncogenic signaling pathways, including the RAS-RAF-MEK-ERK MAPK and AKT-PI3K-mTOR pathways. These pathways then activate many biological outputs that are beneficial to cancer cell proliferation, including their chronic initiation and progression through the cell cycle. Here, we review the molecular mechanisms that regulate EGFR signal transduction, including the EGFR structure and its mutations, ligand binding and EGFR dimerization, as well as the signaling pathways that lead to G1 cell cycle progression. We focus on the induction of CYCLIN D expression, CDK4/6 activation, and the repression of cyclin-dependent kinase inhibitor proteins (CDKi) by EGFR signaling pathways. We also discuss the successes and challenges of EGFR-targeted therapies, and the potential for their use in combination with CDK4/6 inhibitors.
Collapse
Affiliation(s)
- Ping Wee
- Department of Medical Genetics and Signal Transduction Research Group, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB T6G 2H7, Canada.
| | - Zhixiang Wang
- Department of Medical Genetics and Signal Transduction Research Group, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB T6G 2H7, Canada.
| |
Collapse
|
17
|
Corti F, Simons M. Modulation of VEGF receptor 2 signaling by protein phosphatases. Pharmacol Res 2017; 115:107-123. [PMID: 27888154 PMCID: PMC5205541 DOI: 10.1016/j.phrs.2016.11.022] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/04/2016] [Revised: 11/18/2016] [Accepted: 11/21/2016] [Indexed: 12/21/2022]
Abstract
Phosphorylation of serines, threonines, and tyrosines is a central event in signal transduction cascades in eukaryotic cells. The phosphorylation state of any particular protein reflects a balance of activity between kinases and phosphatases. Kinase biology has been exhaustively studied and is reasonably well understood, however, much less is known about phosphatases. A large body of evidence now shows that protein phosphatases do not behave as indiscriminate signal terminators, but can function both as negative or positive regulators of specific signaling pathways. Genetic models have also shown that different protein phosphatases play precise biological roles in health and disease. Finally, genome sequencing has unveiled the existence of many protein phosphatases and associated regulatory subunits comparable in number to kinases. A wide variety of roles for protein phosphatase roles have been recently described in the context of cancer, diabetes, hereditary disorders and other diseases. In particular, there have been several recent advances in our understanding of phosphatases involved in regulation of vascular endothelial growth factor receptor 2 (VEGFR2) signaling. The receptor is the principal signaling molecule mediating a wide spectrum of VEGF signal and, thus, is of paramount significance in a wide variety of diseases ranging from cancer to cardiovascular to ophthalmic. This review focuses on the current knowledge about protein phosphatases' regulation of VEGFR2 signaling and how these enzymes can modulate its biological effects.
Collapse
Affiliation(s)
- Federico Corti
- Yale Cardiovascular Research Center, Department of Internal Medicine and Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA.
| | - Michael Simons
- Yale Cardiovascular Research Center, Department of Internal Medicine and Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA.
| |
Collapse
|
18
|
Dernayka L, Rauch N, Jarboui MA, Zebisch A, Texier Y, Horn N, Romano D, Gloeckner CJ, Kriegsheim AV, Ueffing M, Kolch W, Boldt K. Autophosphorylation on S614 inhibits the activity and the transforming potential of BRAF. Cell Signal 2016; 28:1432-1439. [PMID: 27345148 DOI: 10.1016/j.cellsig.2016.06.016] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Revised: 06/09/2016] [Accepted: 06/18/2016] [Indexed: 12/25/2022]
Abstract
The BRAF proto-oncogene serine/threonine-protein kinase, known as BRAF, belongs to the RAF kinase family. It regulates the MAPK/ERK signalling pathway affecting several cellular processes such as growth, survival, differentiation, and cellular transformation. BRAF is mutated in ~8% of all human cancers with the V600E mutation constituting ~90% of mutations. Here, we have used quantitative mass spectrometry to map and compare phosphorylation site patterns between BRAF and BRAF V600E. We identified sites that are shared as well as several quantitative differences in phosphorylation abundance. The highest difference is phosphorylation of S614 in the activation loop which is ~5fold enhanced in BRAF V600E. Mutation of S614 increases the kinase activity of both BRAF and BRAF V600E and the transforming ability of BRAF V600E. The phosphorylation of S614 is mitogen inducible and the result of autophosphorylation. These data suggest that phosphorylation at this site is inhibitory, and part of the physiological shut-down mechanism of BRAF signalling.
Collapse
Affiliation(s)
- Layal Dernayka
- Medical Proteome Center, Division for Experimental Ophthalmology, Institute for Ophthalmic Research, University of Tuebingen, Tuebingen, Germany
| | - Nora Rauch
- Systems Biology Ireland, University College Dublin, Belfield, Dublin 4, Ireland
| | - Mohamed-Ali Jarboui
- Medical Proteome Center, Division for Experimental Ophthalmology, Institute for Ophthalmic Research, University of Tuebingen, Tuebingen, Germany
| | - Armin Zebisch
- Systems Biology Ireland, University College Dublin, Belfield, Dublin 4, Ireland
| | - Yves Texier
- Medical Proteome Center, Division for Experimental Ophthalmology, Institute for Ophthalmic Research, University of Tuebingen, Tuebingen, Germany
| | - Nicola Horn
- Medical Proteome Center, Division for Experimental Ophthalmology, Institute for Ophthalmic Research, University of Tuebingen, Tuebingen, Germany
| | - David Romano
- Systems Biology Ireland, University College Dublin, Belfield, Dublin 4, Ireland
| | - Christian Johannes Gloeckner
- Medical Proteome Center, Division for Experimental Ophthalmology, Institute for Ophthalmic Research, University of Tuebingen, Tuebingen, Germany; Deutsches Zentrum für Neurodegenerative Erkrankungen e. V., Otfried-Müller Strasse 23, 72076 Tübingen, Germany
| | - Alex von Kriegsheim
- Systems Biology Ireland, University College Dublin, Belfield, Dublin 4, Ireland
| | - Marius Ueffing
- Medical Proteome Center, Division for Experimental Ophthalmology, Institute for Ophthalmic Research, University of Tuebingen, Tuebingen, Germany
| | - Walter Kolch
- Systems Biology Ireland, University College Dublin, Belfield, Dublin 4, Ireland; Conway Institute of Biomolecular & Biomedical Research, University College Dublin, Belfield, Dublin 4, Ireland; School of Medicine and Medical Science, University College Dublin, Belfield, Dublin 4, Ireland.
| | - Karsten Boldt
- Medical Proteome Center, Division for Experimental Ophthalmology, Institute for Ophthalmic Research, University of Tuebingen, Tuebingen, Germany.
| |
Collapse
|
19
|
Cohen JD, Labenski M, Mastrandrea NJ, Canatsey RD, Monks TJ, Lau SS. Transcriptional and post-translational modifications of B-Raf in quinol-thioether induced tuberous sclerosis renal cell carcinoma. Mol Carcinog 2015; 55:1243-50. [PMID: 26333016 DOI: 10.1002/mc.22366] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Revised: 06/05/2015] [Accepted: 06/26/2015] [Indexed: 11/12/2022]
Abstract
Increased activity of B-Raf has been identified in approximately 7% of human cancers. Treatment of Eker rats (Tsc-2(EK/+) ), bearing a mutation in one allele of the tuberous sclerosis-2 (Tsc-2) gene, with the nephrocarcinogen 2,3,5-tris-(glutathion-S-yl) hydroquinone (TGHQ) results in loss of the wild-type allele of Tsc-2 in renal preneoplastic lesions and tumors. These tumors have increased protein expression of B-Raf, C-Raf (Raf-1), and increased expression and activity of ERK kinase. Similar changes are observed in Raf kinases following TGHQ-mediated transformation of primary renal epithelial cells derived from Tsc-2(EK/+) rats (QTRRE cells), cells that are also null for tuberin. Herein, we utilized LC-MS/MS to identify constitutive phosphorylation of S345 and S483 in both 100- and 95-kDa forms of B-Raf in QTRRE cells. Using microRotofor liquid-phase isoelectric focusing, we identified four fractions of B-Raf that contain different post-translational modification profiles in QTRRE cells. Amplification of the kinase domain of B-Raf from QTRRE cells, outer-stripe of the outer medulla of 8-month TGHQ- or vehicle-treated Tsc-2(+/+) and Tsc-2(EK/+) rats, as well as tumors excised from 8-month TGHQ-treated Tsc-2(EK/+) rats revealed three splice variants of B-Raf within the kinase domain. These splice variants differed by approximately 340, 544, and 600 bp; confirmed by sequencing. No point mutations within the kinase domain of B-Raf were identified. In addition, B-Raf/Raf-1/14-3-3 complex formation in the QTRRE cells was decreased by sorafenib, with concomitant selective decreases in p-ERK levels. Transcriptional and post-translational characterization of critical kinases, such as B-Raf, may contribute to the progression of tuberous sclerosis RCC. (246/250) © 2015 Wiley Periodicals, Inc.
Collapse
Affiliation(s)
- Jennifer D Cohen
- Southwest Environmental Health Sciences Center, College of Pharmacy, The University of Arizona, Tucson, Arizona.,Department of Pharmacology and Toxicology, College of Pharmacy, The University of Arizona, Tucson, Arizona
| | - Matthew Labenski
- Southwest Environmental Health Sciences Center, College of Pharmacy, The University of Arizona, Tucson, Arizona.,Department of Pharmacology and Toxicology, College of Pharmacy, The University of Arizona, Tucson, Arizona
| | - Nicholas J Mastrandrea
- Southwest Environmental Health Sciences Center, College of Pharmacy, The University of Arizona, Tucson, Arizona.,Department of Pharmacology and Toxicology, College of Pharmacy, The University of Arizona, Tucson, Arizona
| | - Ryan D Canatsey
- Southwest Environmental Health Sciences Center, College of Pharmacy, The University of Arizona, Tucson, Arizona.,Department of Pharmacology and Toxicology, College of Pharmacy, The University of Arizona, Tucson, Arizona
| | - Terrence J Monks
- Southwest Environmental Health Sciences Center, College of Pharmacy, The University of Arizona, Tucson, Arizona.,Department of Pharmacology and Toxicology, College of Pharmacy, The University of Arizona, Tucson, Arizona
| | - Serrine S Lau
- Southwest Environmental Health Sciences Center, College of Pharmacy, The University of Arizona, Tucson, Arizona.,Department of Pharmacology and Toxicology, College of Pharmacy, The University of Arizona, Tucson, Arizona
| |
Collapse
|
20
|
Ghosh A, Ratha BN, Gayen N, Mroue KH, Kar RK, Mandal AK, Bhunia A. Biophysical Characterization of Essential Phosphorylation at the Flexible C-Terminal Region of C-Raf with 14-3-3ζ Protein. PLoS One 2015; 10:e0135976. [PMID: 26295714 PMCID: PMC4546627 DOI: 10.1371/journal.pone.0135976] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Accepted: 07/28/2015] [Indexed: 02/07/2023] Open
Abstract
Phosphorylation at the C-terminal flexible region of the C-Raf protein plays an important role in regulating its biological activity. Auto-phosphorylation at serine 621 (S621) in this region maintains C-Raf stability and activity. This phosphorylation mediates the interaction between C-Raf and scaffold protein 14-3-3ζ to activate the downstream MEK kinase pathway. In this study, we have defined the interaction of C-terminal peptide sequence of C-Raf with 14-3-3ζ protein and determined the possible structural adaptation of this region. Biophysical elucidation of the interaction was carried out using phosphopeptide (residue number 615–630) in the presence of 14-3-3ζ protein. Using isothermal titration calorimetry (ITC), a high binding affinity with micro-molar range was found to exist between the peptide and 14-3-3ζ protein, whereas the non-phosphorylated peptide did not show any appreciable binding affinity. Further interaction details were investigated using several biophysical techniques such as circular dichroism (CD), fluorescence, and nuclear magnetic resonance (NMR) spectroscopy, in addition to molecular modeling. This study provides the molecular basis for C-Raf C-terminal-derived phosphopeptide interaction with 14-3-3ζ protein as well as structural insights responsible for phosphorylated S621-mediated 14-3-3ζ binding at an atomic resolution.
Collapse
Affiliation(s)
- Anirban Ghosh
- Department of Biophysics, Bose Institute, P-1/12 CIT Scheme VII (M), Kolkata, 700 054, India
| | - Bhisma Narayan Ratha
- Department of Biophysics, Bose Institute, P-1/12 CIT Scheme VII (M), Kolkata, 700 054, India
| | - Nilanjan Gayen
- Department of Molecular Medicine, Bose Institute, P-1/12 CIT Scheme VII (M), Kolkata, 700 054, India
| | - Kamal H. Mroue
- Biophysics and Department of Chemistry, University of Michigan, Ann Arbor, Michigan, 48109–1055, United States of America
| | - Rajiv K. Kar
- Department of Biophysics, Bose Institute, P-1/12 CIT Scheme VII (M), Kolkata, 700 054, India
| | - Atin K. Mandal
- Department of Molecular Medicine, Bose Institute, P-1/12 CIT Scheme VII (M), Kolkata, 700 054, India
- * E-mail: (AKM); (AB)
| | - Anirban Bhunia
- Department of Biophysics, Bose Institute, P-1/12 CIT Scheme VII (M), Kolkata, 700 054, India
- * E-mail: (AKM); (AB)
| |
Collapse
|
21
|
Jensen HA, Bunaciu RP, Varner JD, Yen A. GW5074 and PP2 kinase inhibitors implicate nontraditional c-Raf and Lyn function as drivers of retinoic acid-induced maturation. Cell Signal 2015; 27:1666-75. [PMID: 25817574 PMCID: PMC4529126 DOI: 10.1016/j.cellsig.2015.03.014] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Revised: 03/05/2015] [Accepted: 03/16/2015] [Indexed: 02/07/2023]
Abstract
The multivariate nature of cancer necessitates multi-targeted therapy, and kinase inhibitors account for a vast majority of approved cancer therapeutics. While acute promyelocytic leukemia (APL) patients are highly responsive to retinoic acid (RA) therapy, kinase inhibitors have been gaining momentum as co-treatments with RA for non-APL acute myeloid leukemia (AML) differentiation therapies, especially as a means to treat relapsed or refractory AML patients. In this study GW5074 (a c-Raf inhibitor) and PP2 (a Src-family kinase inhibitor) enhanced RA-induced maturation of t(15;17)-negative myeloblastic leukemia cells and rescued response in RA-resistant cells. PD98059 (a MEK inhibitor) and Akti-1/2 (an Akt inhibitor) were less effective, but did tend to promote maturation-uncoupled G1/G0 arrest, while wortmannin (a PI3K inhibitor) did not enhance differentiation surface marker expression or growth arrest. PD98059 and Akti-1/2 did not enhance differentiation markers and have potential, antagonistic off-targets effects on the aryl hydrocarbon receptor (AhR), but neither could the AhR agonist 6-formylindolo(3,2-b)carbazole (FICZ) rescue differentiation events in the RA-resistant cells. GW5074 rescued early CD38 expression in RA-resistant cells exhibiting an early block in differentiation before CD38 expression, while for RA-resistant cells with differentiation blocked later, PP2 rescued the later differentiation marker CD11b; but surprisingly, the combination of the two was not synergistic. Kinases c-Raf, Src-family kinases Lyn and Fgr, and PI3K display highly correlated signaling changes during RA treatment, while activation of traditional downstream targets (Akt, MEK/ERK), and even the surface marker CD38, were poorly correlated with c-Raf or Lyn during differentiation. This suggests that an interrelated kinase module involving c-Raf, PI3K, Lyn and perhaps Fgr functions in a nontraditional way during RA-induced maturation or during rescue of RA induction therapy using inhibitor co-treatment in RA-resistant leukemia cells.
Collapse
Affiliation(s)
- Holly A Jensen
- School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY, United States
| | - Rodica P Bunaciu
- Department of Biomedical Sciences, Cornell University, Ithaca, NY, United States
| | - Jeffrey D Varner
- School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY, United States
| | - Andrew Yen
- Department of Biomedical Sciences, Cornell University, Ithaca, NY, United States
| |
Collapse
|
22
|
Abstract
RAF family kinases were among the first oncoproteins to be described more than 30 years ago. They primarily act as signalling relays downstream of RAS, and their close ties to cancer have fuelled a large number of studies. However, we still lack a systems-level understanding of their regulation and mode of action. The recent discovery that the catalytic activity of RAF depends on an allosteric mechanism driven by kinase domain dimerization is providing a vital new piece of information towards a comprehensive model of RAF function. The fact that current RAF inhibitors unexpectedly induce ERK signalling by stimulating RAF dimerization also calls for a deeper structural characterization of this family of kinases.
Collapse
|
23
|
Zanucco E, El-Nikhely N, Götz R, Weidmann K, Pfeiffer V, Savai R, Seeger W, Ullrich A, Rapp UR. Elimination of B-RAF in oncogenic C-RAF-expressing alveolar epithelial type II cells reduces MAPK signal intensity and lung tumor growth. J Biol Chem 2014; 289:26804-26816. [PMID: 25096573 DOI: 10.1074/jbc.m114.558999] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Tumors are often greatly dependent on signaling cascades promoting cell growth or survival and may become hypersensitive to inactivation of key components within these signaling pathways. Ras and RAF mutations found in human cancer confer constitutive activity to these signaling molecules thereby converting them into an oncogenic state. RAF dimerization is required for normal Ras-dependent RAF activation and is required for the oncogenic potential of mutant RAFs. Here we describe a new mouse model for lung tumor development to investigate the role of B-RAF in oncogenic C-RAF-mediated adenoma initiation and growth. Conditional elimination of B-RAF in C-RAF BxB-expressing embryonic alveolar epithelial type II cells did not block adenoma formation. However, loss of B-RAF led to significantly reduced tumor growth. The diminished tumor growth upon B-RAF inactivation was due to reduced cell proliferation in absence of senescence and increased apoptosis. Furthermore, B-RAF elimination inhibited C-RAF BxB-mediated activation of the mitogenic cascade. In line with these data, mutation of Ser-621 in C-RAF BxB abrogated in vitro the dimerization with B-RAF and blocked the ability to activate the MAPK cascade. Taken together these data indicate that B-RAF is an important factor in oncogenic C-RAF-mediated tumorigenesis.
Collapse
Affiliation(s)
- Emanuele Zanucco
- Department of Molecular Biology, Max Planck Institute of Biochemistry, 85152 Martinsried, Germany,.
| | - Nefertiti El-Nikhely
- Department of Lung Development and Remodelling, Max Planck Institute for Heart and Lung Research, Member of the German Center for Lung Research (DZL), 61231 Bad Nauheim, Germany, and
| | - Rudolf Götz
- Institute for Medical Radiation and Cell Research (MSZ), University of Würzburg, 97078 Würzburg, Germany
| | - Katharina Weidmann
- Institute for Medical Radiation and Cell Research (MSZ), University of Würzburg, 97078 Würzburg, Germany
| | - Verena Pfeiffer
- Institute for Medical Radiation and Cell Research (MSZ), University of Würzburg, 97078 Würzburg, Germany
| | - Rajkumar Savai
- Department of Lung Development and Remodelling, Max Planck Institute for Heart and Lung Research, Member of the German Center for Lung Research (DZL), 61231 Bad Nauheim, Germany, and
| | - Werner Seeger
- Department of Lung Development and Remodelling, Max Planck Institute for Heart and Lung Research, Member of the German Center for Lung Research (DZL), 61231 Bad Nauheim, Germany, and
| | - Axel Ullrich
- Department of Molecular Biology, Max Planck Institute of Biochemistry, 85152 Martinsried, Germany
| | - Ulf R Rapp
- Department of Molecular Biology, Max Planck Institute of Biochemistry, 85152 Martinsried, Germany,.
| |
Collapse
|
24
|
Hwang YC, Yang CH, Lin CH, Ch'ang HJ, Chang VHS, Yu WCY. Destabilization of KLF10, a tumor suppressor, relies on thr93 phosphorylation and isomerase association. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1833:3035-3045. [PMID: 23994618 DOI: 10.1016/j.bbamcr.2013.08.010] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2013] [Revised: 08/08/2013] [Accepted: 08/12/2013] [Indexed: 12/24/2022]
Abstract
KLF10 is now classified as a member of the Krüppel-like transcription factor family and acts as a tumor suppressor. Although KLF10 is originally named as TGF-β-inducible early gene-1 and mimicking the anti-proliferative effect of TGF-β in various carcinoma cells, the transcriptional upregulatory function of KLF10 has been described for a variety of cytokines and in many diseases. Through in vivo and in vitro phosphorylation assays, we identified that KLF10 is a phosphorylated protein in cells. Using yeast-two hybrid screening and site direct mutagenesis, we also identified PIN1 as a novel KLF10 associated protein. PIN1 is a peptidyl-prolyl isomerase enzyme belonging to the parvulin family, which specifically recognizes phosphorylated Ser/Thr-Pro containing substrates. Through protein-protein interaction assays, we showed that the Pro-directed Ser/Thr-Pro motif at Thr-93 in the KLF10 N-terminal region is essential for the interaction between KLF10 and PIN1. More importantly, PIN1 interacts with KLF10 in a phosphorylation-dependent manner and this interaction promotes KLF10 protein degradation in cells. Therefore, KLF10 shows shorter protein stability compared with mutant KLF10 that lacks PIN1 binding ability after cycloheximide treatments. The reversely correlated expression profile between KLF10 and PIN1 as observed in cell lines was also shown in clinic pancreatic cancer specimen. Using in vitro kinase assays and depletion assays, we were able to show that RAF-1 phosphorylates the Thr-93 of KLF10 and affects the KLF10 expression level in cells. Thus these findings as a whole indicate that RAF-1 phosphorylation and PIN1 isomerization together regulate KLF10 stability and further affect the role of KLF10 in tumor progression.
Collapse
Affiliation(s)
- Yu-Chyi Hwang
- National Institute of Cancer Research, National Health Research Institutes, Tainan, Taiwan
| | - Chien-Hui Yang
- National Institute of Cancer Research, National Health Research Institutes, Tainan, Taiwan
| | - Ching-Hui Lin
- National Institute of Cancer Research, National Health Research Institutes, Tainan, Taiwan
| | - Hui-Ju Ch'ang
- National Institute of Cancer Research, National Health Research Institutes, Tainan, Taiwan
| | - Vincent H S Chang
- Program for Translation Medicine, College of Medical Science and Technology, Taipei Medical University, Taiwan.
| | - Winston C Y Yu
- National Institute of Cancer Research, National Health Research Institutes, Tainan, Taiwan; College of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan.
| |
Collapse
|
25
|
Goncharova EA, Khavin IS, Goncharov DA, Krymskaya VP. Differential effects of formoterol on thrombin- and PDGF-induced proliferation of human pulmonary arterial vascular smooth muscle cells. Respir Res 2012. [PMID: 23186269 PMCID: PMC3545871 DOI: 10.1186/1465-9921-13-109] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Background Increased pulmonary arterial vascular smooth muscle (PAVSM) cell proliferation is a key pathophysiological component of pulmonary vascular remodeling in pulmonary arterial hypertension (PH). The long-acting β2-adrenergic receptor (β2AR) agonist formoterol, a racemate comprised of (R,R)- and (S,S)-enantiomers, is commonly used as a vasodilator in chronic obstructive pulmonary disease (COPD). PH, a common complication of COPD, increases patients’ morbidity and reduces survival. Recent studies demonstrate that formoterol has anti-proliferative effects on airway smooth muscle cells and bronchial fibroblasts. The effects of formoterol and its enantiomers on PAVSM cell proliferation are not determined. The goals of this study were to examine effects of racemic formoterol and its enantiomers on PAVSM cell proliferation as it relates to COPD-associated PH. Methods Basal, thrombin-, PDGF- and chronic hypoxia-induced proliferation of primary human PAVSM cells was examined by DNA synthesis analysis using BrdU incorporation assay. ERK1/2, mTORC1 and mTORC2 activation were determined by phosphorylation levels of ERK1/2, ribosomal protein S6 and S473-Akt using immunoblot analysis. Results We found that (R,R) and racemic formoterol inhibited basal, thrombin- and chronic hypoxia-induced proliferation of human PAVSM cells while (S,S) formoterol had lesser inhibitory effect. The β2AR blocker propranolol abrogated the growth inhibitory effect of formoterol. (R,R), but not (S,S) formoterol attenuated basal, thrombin- and chronic hypoxia-induced ERK1/2 phosphorylation, but had little effect on Akt and S6 phosphorylation levels. Formoterol and its enantiomers did not significantly affect PDGF-induced DNA synthesis and PDGF-dependent ERK1/2, S473-Akt and S6 phosphorylation in human PAVSM cells. Conclusions Formoterol inhibits basal, thrombin-, and chronic hypoxia-, but not PDGF-induced human PAVSM cell proliferation and ERK1/2, but has little effect on mTORC1 and mTORC2 signaling. Anti-proliferative effects of formoterol depend predominantly on its (R,R) enantiomer and require the binding with β2AR. These data suggest that (R,R) formoterol may be considered as potential adjuvant therapy to inhibit PAVSM cell proliferation in COPD-associated PH.
Collapse
Affiliation(s)
- Elena A Goncharova
- Pulmonary, Allergy & Critical Care Division, Department of Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA.
| | | | | | | |
Collapse
|
26
|
Krishnan J, Choi S. Systems Biological Approaches Reveal Non-additive Responses and Multiple Crosstalk Mechanisms between TLR and GPCR Signaling. Genomics Inform 2012; 10:153-66. [PMID: 23166526 PMCID: PMC3492651 DOI: 10.5808/gi.2012.10.3.153] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2012] [Revised: 07/14/2012] [Accepted: 07/20/2012] [Indexed: 12/30/2022] Open
Abstract
A variety of ligands differ in their capacity to bind the receptor, elicit gene expression, and modulate physiological responses. Such receptors include Toll-like receptors (TLRs), which recognize various patterns of pathogens and lead to primary innate immune activation against invaders, and G-protein coupled receptors (GPCRs), whose interaction with their cognate ligands activates heterotrimeric G proteins and regulates specific downstream effectors, including immuno-stimulating molecules. Once TLRs are activated, they lead to the expression of hundreds of genes together and bridge the arm of innate and adaptive immune responses. We characterized the gene expression profile of Toll-like receptor 4 (TLR4) in RAW 264.7 cells when it bound with its ligand, 2-keto-3-deoxyoctonate (KDO), the active part of lipopolysaccharide. In addition, to determine the network communications among the TLR, Janus kinase (JAK)/signal transducer and activator of transcription (STAT), and GPCR, we tested RAW 264.7 cells with KDO, interferon-β, or cAMP analog 8-Br. The ligands were also administered as a pair of double and triple combinations.
Collapse
Affiliation(s)
- Jayalakshmi Krishnan
- Department of Molecular Science and Technology, Ajou University, Suwon 443-749, Korea
| | | |
Collapse
|
27
|
McCubrey JA, Steelman LS, Chappell WH, Abrams SL, Montalto G, Cervello M, Nicoletti F, Fagone P, Malaponte G, Mazzarino MC, Candido S, Libra M, Bäsecke J, Mijatovic S, Maksimovic-Ivanic D, Milella M, Tafuri A, Cocco L, Evangelisti C, Chiarini F, Martelli AM. Mutations and deregulation of Ras/Raf/MEK/ERK and PI3K/PTEN/Akt/mTOR cascades which alter therapy response. Oncotarget 2012; 3:954-87. [PMID: 23006971 PMCID: PMC3660063 DOI: 10.18632/oncotarget.652] [Citation(s) in RCA: 217] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2012] [Accepted: 09/17/2012] [Indexed: 02/07/2023] Open
Abstract
The Ras/Raf/MEK/ERK and PI3K/PTEN/Akt/mTOR cascades are often activated by genetic alterations in upstream signaling molecules such as receptor tyrosine kinases (RTK). Certain components of these pathways, RAS, NF1, BRAF, MEK1, DUSP5, PP2A, PIK3CA, PIK3R1, PIK3R4, PIK3R5, IRS4, AKT, NFKB1, MTOR, PTEN, TSC1, and TSC2 may also be activated/inactivated by mutations or epigenetic silencing. Upstream mutations in one signaling pathway or even in downstream components of the same pathway can alter the sensitivity of the cells to certain small molecule inhibitors. These pathways have profound effects on proliferative, apoptotic and differentiation pathways. Dysregulation of components of these cascades can contribute to: resistance to other pathway inhibitors, chemotherapeutic drug resistance, premature aging as well as other diseases. This review will first describe these pathways and discuss how genetic mutations and epigenetic alterations can result in resistance to various inhibitors.
Collapse
Affiliation(s)
- James A McCubrey
- Department of Microbiology and Immunology, Brody School of Medicine at East Carolina University, Greenville, NC, USA.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
28
|
Dalton GD, Howlett AC. Cannabinoid CB1 receptors transactivate multiple receptor tyrosine kinases and regulate serine/threonine kinases to activate ERK in neuronal cells. Br J Pharmacol 2012; 165:2497-511. [PMID: 21518335 DOI: 10.1111/j.1476-5381.2011.01455.x] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND AND PURPOSE Signalling networks that regulate the progression of cannabinoid CB(1) receptor-mediated extracellular signal-regulated kinase (ERK) activation in neurons are poorly understood. We investigated the cellular mechanisms involved in CB(1) receptor-stimulated ERK phosphorylation in a neuronal cell model. EXPERIMENTAL APPROACH Murine N18TG2 neuronal cells were used to analyse the effect of specific protein kinase and phosphatase inhibitors on CB(1) receptor-stimulated ERK phosphorylation. The LI-COR In Cell Western assay and immunoblotting were used to measure ERK phosphorylation. KEY RESULTS The time-course of CB(1) receptor-stimulated ERK activation occurs in three phases that are regulated by distinct cellular mechanisms in N18TG2 cells. Phase I (0-5 min) maximal ERK phosphorylation is mediated by CB(1) receptor-stimulated ligand-independent transactivation of multiple receptor tyrosine kinases (RTKs). Phase I requires G(i/o) βγ subunit-stimulated phosphatidylinositol 3-kinase activation and Src kinase activation and is modulated by inhibition of cAMP-activated protein kinase A (PKA) levels. Src kinase activation is regulated by the protein tyrosine phosphatases 1B and Shp1. The Phase II (5-10 min) rapid decline in ERK phosphorylation involves PKA inhibition and serine/threonine phosphatase PP1/PP2A activation. The Phase III (>10 min) plateau in ERK phosphorylation is mediated by CB(1) receptor-stimulated, ligand-independent, transactivation of multiple RTKs. CONCLUSIONS AND IMPLICATIONS The complex expression of CB(1) receptor-stimulated ERK activation provides cellular selectivity, modulation of sensitivity to agonists, and coincidence detection with RTK signalling. RTK and PKA pathways may provide routes to novel CB(1) -based therapeutic interventions in the treatment of addictive disorders or neurodegenerative diseases. LINKED ARTICLES This article is part of a themed section on Cannabinoids in Biology and Medicine. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.165.issue-8. To view Part I of Cannabinoids in Biology and Medicine visit http://dx.doi.org/10.1111/bph.2011.163.issue-7.
Collapse
Affiliation(s)
- George D Dalton
- Department of Physiology and Pharmacology, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA
| | | |
Collapse
|
29
|
Miller MA, Feng XJ, Li G, Rabitz HA. Identifying biological network structure, predicting network behavior, and classifying network state with High Dimensional Model Representation (HDMR). PLoS One 2012; 7:e37664. [PMID: 22723838 PMCID: PMC3377689 DOI: 10.1371/journal.pone.0037664] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2011] [Accepted: 04/26/2012] [Indexed: 11/26/2022] Open
Abstract
This work presents an adapted Random Sampling - High Dimensional Model Representation (RS-HDMR) algorithm for synergistically addressing three key problems in network biology: (1) identifying the structure of biological networks from multivariate data, (2) predicting network response under previously unsampled conditions, and (3) inferring experimental perturbations based on the observed network state. RS-HDMR is a multivariate regression method that decomposes network interactions into a hierarchy of non-linear component functions. Sensitivity analysis based on these functions provides a clear physical and statistical interpretation of the underlying network structure. The advantages of RS-HDMR include efficient extraction of nonlinear and cooperative network relationships without resorting to discretization, prediction of network behavior without mechanistic modeling, robustness to data noise, and favorable scalability of the sampling requirement with respect to network size. As a proof-of-principle study, RS-HDMR was applied to experimental data measuring the single-cell response of a protein-protein signaling network to various experimental perturbations. A comparison to network structure identified in the literature and through other inference methods, including Bayesian and mutual-information based algorithms, suggests that RS-HDMR can successfully reveal a network structure with a low false positive rate while still capturing non-linear and cooperative interactions. RS-HDMR identified several higher-order network interactions that correspond to known feedback regulations among multiple network species and that were unidentified by other network inference methods. Furthermore, RS-HDMR has a better ability to predict network response under unsampled conditions in this application than the best statistical inference algorithm presented in the recent DREAM3 signaling-prediction competition. RS-HDMR can discern and predict differences in network state that arise from sources ranging from intrinsic cell-cell variability to altered experimental conditions, such as when drug perturbations are introduced. This ability ultimately allows RS-HDMR to accurately classify the experimental conditions of a given sample based on its observed network state.
Collapse
Affiliation(s)
- Miles A Miller
- Department of Chemistry, Princeton University, Princeton, New Jersey, USA
| | | | | | | |
Collapse
|
30
|
Matallanas D, Birtwistle M, Romano D, Zebisch A, Rauch J, von Kriegsheim A, Kolch W. Raf family kinases: old dogs have learned new tricks. Genes Cancer 2011; 2:232-60. [PMID: 21779496 PMCID: PMC3128629 DOI: 10.1177/1947601911407323] [Citation(s) in RCA: 272] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
First identified in the early 1980s as retroviral oncogenes, the Raf proteins have been the objects of intense research. The discoveries 10 years later that the Raf family members (Raf-1, B-Raf, and A-Raf) are bona fide Ras effectors and upstream activators of the ubiquitous ERK pathway increased the interest in these proteins primarily because of the central role that this cascade plays in cancer development. The important role of Raf in cancer was corroborated in 2002 with the discovery of B-Raf genetic mutations in a large number of tumors. This led to intensified drug development efforts to target Raf signaling in cancer. This work yielded not only recent clinical successes but also surprising insights into the regulation of Raf proteins by homodimerization and heterodimerization. Surprising insights also came from the hunt for new Raf targets. Although MEK remains the only widely accepted Raf substrate, new kinase-independent roles for Raf proteins have emerged. These include the regulation of apoptosis by suppressing the activity of the proapoptotic kinases, ASK1 and MST2, and the regulation of cell motility and differentiation by controlling the activity of Rok-α. In this review, we discuss the regulation of Raf proteins and their role in cancer, with special focus on the interacting proteins that modulate Raf signaling. We also describe the new pathways controlled by Raf proteins and summarize the successes and failures in the development of efficient anticancer therapies targeting Raf. Finally, we also argue for the necessity of more systemic approaches to obtain a better understanding of how the Ras-Raf signaling network generates biological specificity.
Collapse
Affiliation(s)
- David Matallanas
- Systems Biology Ireland, University College Dublin, Dublin, Ireland
| | | | | | | | | | | | | |
Collapse
|
31
|
Udell CM, Rajakulendran T, Sicheri F, Therrien M. Mechanistic principles of RAF kinase signaling. Cell Mol Life Sci 2011; 68:553-65. [PMID: 20820846 PMCID: PMC11114552 DOI: 10.1007/s00018-010-0520-6] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2010] [Revised: 08/24/2010] [Accepted: 08/25/2010] [Indexed: 12/19/2022]
Abstract
The RAF family of kinases are key components acting downstream of receptor tyrosine kinases and cells employ several distinct mechanisms to strictly control their activity. RAF transitions from an inactive state, where the N-terminal regulatory region binds intramolecularly to the C-terminal kinase domain, to an open state capable of executing the phosphoryl transfer reaction. This transition involves changes both within and between the protein domains in RAF. Many different proteins regulate the transition between inactive and active states of RAF, including RAS and KSR, which are arguably the two most prominent regulators of RAF function. Recent developments have added several new twists to our understanding of RAF regulation. Among others, dimerization of the RAF kinase domain is emerging as a crucial step in the RAF activation process. The multitude of regulatory protein-protein interactions involving RAF remains a largely untapped area for therapeutic applications.
Collapse
Affiliation(s)
- Christian M. Udell
- Laboratory of Intracellular Signaling, Département de pathologie et de biologie cellulaire, Institute for Research in Immunology and Cancer, Université de Montréal, C.P. 6128, Succursale Centre-Ville, Montreal, QC H3C 3J7 Canada
| | - Thanashan Rajakulendran
- Centre for Systems Biology, Samuel Lunenfeld Research Institute, Toronto, ON M5G 1X5 Canada
- Department of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8 Canada
| | - Frank Sicheri
- Centre for Systems Biology, Samuel Lunenfeld Research Institute, Toronto, ON M5G 1X5 Canada
- Department of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8 Canada
| | - Marc Therrien
- Laboratory of Intracellular Signaling, Département de pathologie et de biologie cellulaire, Institute for Research in Immunology and Cancer, Université de Montréal, C.P. 6128, Succursale Centre-Ville, Montreal, QC H3C 3J7 Canada
| |
Collapse
|
32
|
Shupe J, Cheng J, Puri P, Kostereva N, Walker WH. Regulation of Sertoli-germ cell adhesion and sperm release by FSH and nonclassical testosterone signaling. Mol Endocrinol 2010; 25:238-52. [PMID: 21177760 DOI: 10.1210/me.2010-0030] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Testosterone and FSH act in synergy to produce the factors required to maximize the production of spermatozoa and male fertility. However, the molecular mechanisms by which these hormones support spermatogenesis are not well established. Recently, we identified a nonclassical mechanism of testosterone signaling in cultured rat Sertoli cells. We found that testosterone binding to the androgen receptor recruits and activates Src tyrosine kinase. Src then causes the activation of the epidermal growth factor receptor, which results in the phosphorylation and activation of the ERK MAPK and the cAMP response element-binding protein transcription factor. In this report, we find that FSH inhibits testosterone-mediated activation of ERK and the MAPK pathway in Sertoli cells via the protein kinase A-mediated inhibition of Raf kinase. In addition, FSH, as well as inhibitors of Src and ERK kinase activity, reduced germ cell attachment to Sertoli cells in culture. Using pathway-specific androgen receptor mutants we found that the nonclassical pathway is required for testosterone-mediated increases in germ cell attachment to Sertoli cells. Studies of seminiferous tubule explants determined that Src kinase, but not ERK kinase, activity is required for the release of sperm from seminiferous tubule explants. These findings suggest the nonclassical testosterone-signaling pathway acts via Src and ERK kinases to facilitate the adhesion of immature germ cells to Sertoli cells and through Src to permit the release of mature spermatozoa. In contrast, FSH acts to limit testosterone-mediated ERK kinase activity and germ cell attachment.
Collapse
Affiliation(s)
- John Shupe
- Center for Research in Reproductive Physiology, Department of Cell Biology and Molecular Physiology, Magee Women’s Research Institute, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA
| | | | | | | | | |
Collapse
|
33
|
Walker WH. Non-classical actions of testosterone and spermatogenesis. Philos Trans R Soc Lond B Biol Sci 2010; 365:1557-69. [PMID: 20403869 DOI: 10.1098/rstb.2009.0258] [Citation(s) in RCA: 174] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Testosterone is essential to maintain spermatogenesis and male fertility. In the absence of testosterone stimulation, spermatogenesis does not proceed beyond the meiosis stage. After withdrawal of testosterone, germ cells that have progressed beyond meiosis detach from supporting Sertoli cells and die, whereas mature sperm cannot be released from Sertoli cells resulting in infertility. The classical mechanism of testosterone action in which testosterone activates gene transcription by causing the androgen receptor to translocate to and bind specific DNA regulatory elements does not appear to fully explain testosterone regulation of spermatogenesis. This review discusses two non-classical testosterone signalling pathways in Sertoli cells and their potential effects on spermatogenesis. Specifically, testosterone-mediated activation of phospholipase C and calcium influx into Sertoli cells is described. Also, testosterone activation of Src, EGF receptor and ERK kinases as well as the activation of the CREB transcription factor and CREB-mediated transcription is reviewed. Regulation of germ cell adhesion to Sertoli cells and release of mature sperm from Sertoli cells by kinases regulated by the non-classical testosterone pathway is discussed. The evidence accumulated suggests that classical and non-classical testosterone signalling contribute to the maintenance of spermatogenesis and male fertility.
Collapse
Affiliation(s)
- William H Walker
- Department of Cell Biology and Physiology, Magee Women's Research Institute, University of Pittsburgh, 204 Craft Avenue, Room B305, Pittsburgh, PA 15261, USA.
| |
Collapse
|
34
|
Rhim JH, Jang IS, Kwon ST, Song KY, Yeo EJ, Park SC. Activation of Wound Healing in Aged Rats by Altering the Cellular Mitogenic Potential. J Gerontol A Biol Sci Med Sci 2010; 65:704-11. [DOI: 10.1093/gerona/glq065] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
|
35
|
Dhillon AS, Yip YY, Grindlay GJ, Pakay JL, Dangers M, Hillmann M, Clark W, Pitt A, Mischak H, Kolch W. The C-terminus of Raf-1 acts as a 14-3-3-dependent activation switch. Cell Signal 2009; 21:1645-51. [PMID: 19595761 DOI: 10.1016/j.cellsig.2009.07.001] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2009] [Revised: 07/01/2009] [Accepted: 07/02/2009] [Indexed: 01/08/2023]
Abstract
The Raf-1 protein kinase is a major activator of the ERK MAPK pathway, which links signaling by a variety of cell surface receptors to the regulation of cell proliferation, survival, differentiation and migration. Signaling by Raf-1 is regulated by a complex and poorly understood interplay between phosphorylation events and protein-protein interactions. One important mode of Raf-1 regulation involves the phosphorylation-dependent binding of 14-3-3 proteins. Here, we have examined the mechanism whereby the C-terminal 14-3-3 binding site of Raf-1, S621, controls the activation of MEK-ERK signaling. We show that phosphorylation of S621 turns over rapidly and is enriched in the activated pool of endogenous Raf-1. The phosphorylation on this site can be mediated by Raf-1 itself but also by other kinase(s). Mutations that prevent the binding of 14-3-3 proteins to S621 render Raf-1 inactive by specifically disrupting its capacity to bind to ATP, and not by gross conformational alteration as indicated by intact MEK binding. Phosphorylation of S621 correlates with the inhibition of Raf-1 catalytic activity in vitro, but 14-3-3 proteins can completely reverse this inhibition. Our findings suggest that 14-3-3 proteins function as critical cofactors in Raf-1 activation, which induce and maintain the protein in a state that is competent for both ATP binding and MEK phosphorylation.
Collapse
Affiliation(s)
- Amardeep S Dhillon
- Department of Biochemistry and Molecular Biology, Bio21 Institute of Molecular Bioscience and Biotechnology, University of Melbourne, 30 Flemington Road, Parkville, VIC 3010, Australia.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
36
|
Yu C, Han W, Shi T, Lv B, He Q, Zhang Y, Li T, Zhang Y, Song Q, Wang L, Ma D. PTPIP51, a novel 14–3–3 binding protein, regulates cell morphology and motility via Raf–ERK pathway. Cell Signal 2008; 20:2208-20. [DOI: 10.1016/j.cellsig.2008.07.020] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2008] [Revised: 07/29/2008] [Accepted: 07/29/2008] [Indexed: 11/30/2022]
|
37
|
|
38
|
Noble C, Mercer K, Hussain J, Carragher L, Giblett S, Hayward R, Patterson C, Marais R, Pritchard CA. CRAF autophosphorylation of serine 621 is required to prevent its proteasome-mediated degradation. Mol Cell 2008; 31:862-72. [PMID: 18922468 DOI: 10.1016/j.molcel.2008.08.026] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2007] [Revised: 06/06/2008] [Accepted: 08/13/2008] [Indexed: 11/17/2022]
Abstract
The CRAF protein kinase regulates proliferative, differentiation, and survival signals from activated RAS proteins to downstream effectors, most often by inducing MEK/ERK activation. A well-established model of CRAF regulation involves RAS-mediated translocation of CRAF to the plasma membrane, where it is activated by a series of events including phosphorylation. Here we have discovered a new mode of regulation that occurs prior to this step. By creating a kinase-defective version of CRAF in mice or by use of the RAF inhibitor sorafenib, we show that CRAF must first undergo autophosphorylation of serine 621 (S621). Autophosphorylation occurs in cis, does not involve MEK/ERK activation, and is essential to ensure the correct folding and stability of the protein. In the absence of S621 phosphorylation, CRAF is degraded by the proteasome by mechanisms that do not uniquely rely on the E3 ubiquitin ligase CHIP.
Collapse
Affiliation(s)
- Catherine Noble
- Department of Biochemistry, Henry Wellcome Building, University of Leicester, Lancaster Road, Leicester LE1 9HN, UK
| | | | | | | | | | | | | | | | | |
Collapse
|
39
|
Baljuls A, Schmitz W, Mueller T, Zahedi RP, Sickmann A, Hekman M, Rapp UR. Positive regulation of A-RAF by phosphorylation of isoform-specific hinge segment and identification of novel phosphorylation sites. J Biol Chem 2008; 283:27239-54. [PMID: 18662992 DOI: 10.1074/jbc.m801782200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In mammals the RAF family of serine/threonine kinases consists of three members, A-, B-, and C-RAF. Activation of RAF kinases involves a complex series of phosphorylations. Although the most prominent phosphorylation sites of B- and C-RAF are well characterized, little is known about regulatory phosphorylation of A-RAF. Using mass spectrometry, we identified here a number of novel in vivo phosphorylation sites in A-RAF. In particular, we found that Ser-432 participates in MEK binding and is indispensable for A-RAF signaling. On the other hand, phosphorylation within the activation segment does not contribute to epidermal growth factor-mediated activation. Furthermore, we show that the potential 14-3-3 binding domains in A-RAF are phosphorylated independently of its activation status. Of importance, we identified a novel regulatory domain in A-RAF (referred to as IH-segment) positioned between amino acids 248 and 267 that contains seven putative phosphorylation sites. Three of these sites, serines 257, 262, and 264, regulate A-RAF activation in a stimulatory manner. The spatial model of the A-RAF fragment, including residues between Ser-246 and Glu-277, revealed a switch of charge at the molecular surface of the IH-region upon phosphorylation, suggesting a mechanism in which the high accumulation of negative charges may lead to an electrostatic destabilization of protein-membrane interaction resulting in depletion of A-RAF from the plasma membrane. Together, we provide here for the first time a detailed analysis of in vivo A-RAF phosphorylation status and demonstrate that regulation of A-RAF by phosphorylation exhibits unique features compared with B- and C-RAF.
Collapse
Affiliation(s)
- Angela Baljuls
- Institute for Medical Radiation and Cell Research, University of Wuerzburg, 97078 Wuerzburg, Germany
| | | | | | | | | | | | | |
Collapse
|
40
|
Gerits N, Kostenko S, Shiryaev A, Johannessen M, Moens U. Relations between the mitogen-activated protein kinase and the cAMP-dependent protein kinase pathways: comradeship and hostility. Cell Signal 2008; 20:1592-607. [PMID: 18423978 DOI: 10.1016/j.cellsig.2008.02.022] [Citation(s) in RCA: 142] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2007] [Revised: 02/28/2008] [Accepted: 02/29/2008] [Indexed: 01/05/2023]
Abstract
Inter- and intracellular communications and responses to environmental changes are pivotal for the orchestrated and harmonious operation of multi-cellular organisms. These well-tuned functions in living organisms are mediated by the action of signal transduction pathways, which are responsible for receiving a signal, transmitting and amplifying it, and eliciting the appropriate cellular responses. Mammalian cells posses numerous signal transduction pathways that, rather than acting in solitude, interconnect with each other, a phenomenon referred to as cross-talk. This allows cells to regulate the distribution, duration, intensity and specificity of the response. The cAMP/cAMP-dependent protein kinase (PKA) pathway and the mitogen-activated protein kinase (MAPK) cascades modulate common processes in the cell and multiple levels of cross-talk between these signalling pathways have been described. The first- and best-characterized interconnections are the PKA-dependent inhibition of the MAPKs ERK1/2 mediated by RAF-1, and PKA-induced activation of ERK1/2 interceded through B-RAF. Recently, novel interactions between components of these pathways and new mechanisms for cross-talk have been elucidated. This review discusses both known and novel interactions between compounds of the cAMP/PKA and MAPKs signalling pathways in mammalian cells.
Collapse
Affiliation(s)
- Nancy Gerits
- Department of Microbiology and Virology, University of Tromsø, N-9037 Tromsø, Norway
| | | | | | | | | |
Collapse
|
41
|
Moretó J, Lladó A, Vidal-Quadras M, Calvo M, Pol A, Enrich C, Tebar F. Calmodulin modulates H-Ras mediated Raf-1 activation. Cell Signal 2008; 20:1092-103. [PMID: 18356021 DOI: 10.1016/j.cellsig.2008.01.022] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2007] [Revised: 01/22/2008] [Accepted: 01/23/2008] [Indexed: 01/08/2023]
Abstract
We have previously demonstrated that, in COS-1 cells, inhibition of calmodulin increases Ras-GTP levels although it decreases Raf-1 activity and consequently MAPK. The present study analyzes the role of calmodulin in the regulation of Raf-1. First we show, using FRET microscopy, that inhibition of Raf-1 was not a consequence of a decreased interaction between H-Ras and Raf-1. Besides, the analysis of the phosphorylation state of Raf-1 showed that calmodulin, through downstream PI3K, is essential to ensure the Ser338-Raf-1 phosphorylation, critical for Raf-1 activation. We also show that the expression of a dominant negative mutant of PI3K impairs the calmodulin-mediated Raf-1 activation; in addition, both calmodulin and PI3K inhibitors decrease phospho-Ser338 and Raf-1 activity from upstream active H-Ras (H-RasG12V) and this effect is dependent on endocytosis. Importantly, in H-Ras depleted COS-1 cells, calmodulin does not modulate MAPK activation. Altogether, the results suggest that calmodulin regulation of MAPK in COS-1 cells relies upon H-Ras control of Raf-1 activity and involves PI3K.
Collapse
Affiliation(s)
- Jemina Moretó
- Departament de Biologia Cel.lular, Facultat de Medicina, Universitat de Barcelona, Casanova 143, 08036-Barcelona, Spain
| | | | | | | | | | | | | |
Collapse
|
42
|
Tosca L, Chabrolle C, Crochet S, Tesseraud S, Dupont J. IGF-1 receptor signaling pathways and effects of AMPK activation on IGF-1-induced progesterone secretion in hen granulosa cells. Domest Anim Endocrinol 2008; 34:204-16. [PMID: 17478073 DOI: 10.1016/j.domaniend.2007.03.001] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2007] [Revised: 02/28/2007] [Accepted: 03/19/2007] [Indexed: 01/18/2023]
Abstract
IGF-1 plays a key role in the proliferation and differentiation of granulosa cells. However, the molecular mechanism of IGF-1 action in avian granulosa cells during follicle maturation is unclear. Here, we first studied IGF-1 receptor (IGF-1R) expression, IGF-1-induced progesterone production and some IGF-1R signaling pathways in granulosa cells from different follicles. IGF-1R (mRNA and protein) was higher in fresh or cultured granulosa cells from the largest follicles (F1 or F2) than in those from smaller follicles (F3 or F4). In vitro, IGF-1 treatment (10(-8)M, 36h) increased progesterone secretion by four-fold in mixed F3 and F4 (F3/4) granulosa cells and by 1.5-fold in F1 granulosa cells. IGF-1 (10(-8)M, 30min)-induced increases in tyrosine phosphorylation of IGF-1R beta subunit and phosphorylation of ERK were higher in F1 than in F3/4 granulosa cells. Interestingly, IGF-1 stimulation (10(-8)M, 10min) decreased the level of AMPK Thr172 phosphorylation in F1 and F3/4 granulosa cells. We have recently showed that AMPK (AMP-activated protein kinase) is a protein kinase involved in the steroidogenesis in chicken granulosa cells. We then studied the effects of AMPK activation by AICAR (5-aminoimidazole-4-carboxamide ribonucleoside), an activator of AMPK, on IGF-1-induced progesterone secretion by F3/4 and F1 granulosa cells. AICAR treatment (1mM, 36h) increased IGF-1-induced progesterone secretion, StAR protein levels and decreased ERK phosphorylation in F1 granulosa cells. Opposite data were observed in F3/4 granulosa cells. Adenovirus-mediated expression of dominant negative AMPK totally reversed the effects of AICAR on IGF-1-induced progesterone secretion, StAR protein production and ERK phosphorylation in both F3/4 and F1 granulosa cells. Thus, a variation of energy metabolism through AMPK activation could modulate differently IGF-1-induced progesterone production in F1 and F3/4 granulosa cells.
Collapse
Affiliation(s)
- Lucie Tosca
- INRA, UMR 6175, Unité de physiologie de la Reproduction et des Comportements, 37380 Nouzilly, France
| | | | | | | | | |
Collapse
|
43
|
|
44
|
Wang J, Yen A. A MAPK-positive feedback mechanism for BLR1 signaling propels retinoic acid-triggered differentiation and cell cycle arrest. J Biol Chem 2007; 283:4375-86. [PMID: 18006504 DOI: 10.1074/jbc.m708471200] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
MAPK signaling is required for retinoic acid (RA)-triggered G(0) cell cycle arrest and cell differentiation, but the mechanism is not well defined. In this study, RA is found to cause MAPK activation with sustained association of RAF to MEK or ERK, leading to a MAPK-dependent accumulation of p21(Waf1/Cip1) and binding to CDK2 blocking G(1)/S transition. BLR1, a chemokine receptor, was found to function as a critical component of RA-triggered MAPK signaling. Unlike wild-type parental cells, RA-treated BLR1 knock-out cells failed to show RAF and consequential MEK and ERK phosphorylation, failed to accumulate CDK inhibitors that control G(1)/S transition, and failed to differentiate and arrest in response to RA, whereas ectopically overexpressing BLR1 enhanced MAPK signaling and caused accelerated RA-induced differentiation and arrest. Ectopic overexpression of RAF enhanced BLR1 expression in response to RA, whereas inhibition of RAF or MEK by inhibitors or knockdown of RAF by short interfering RNA diminished RA-induced BLR1 expression and attenuated differentiation and growth arrest. Ectopic expression of the RAF CR3, the catalytically active domain, in the BLR1 knock-out restored RA-induced MAPK activation and the ability to differentiate and arrest, indicating that RAF effects MAPK signaling by BLR1 to propel differentiation/arrest. Taken together, RA induces cell differentiation and growth arrest through activation of a novel MAPK pathway with BLR1 as a critical component in a positive feedback mechanism that may contribute to the prolonged MAPK signaling propelling RA-induced cell cycle arrest and differentiation.
Collapse
Affiliation(s)
- Jianrong Wang
- Department of Biomedical Sciences, Cornell University, Ithaca, New York 14853, USA
| | | |
Collapse
|
45
|
von Bülow V, Dubben S, Engelhardt G, Hebel S, Plümäkers B, Heine H, Rink L, Haase H. Zinc-dependent suppression of TNF-alpha production is mediated by protein kinase A-induced inhibition of Raf-1, I kappa B kinase beta, and NF-kappa B. THE JOURNAL OF IMMUNOLOGY 2007; 179:4180-6. [PMID: 17785857 DOI: 10.4049/jimmunol.179.6.4180] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Excessive and permanent cytokine production in response to bacterial LPS causes cell and tissue damage, and hence organ failure during sepsis. We have previously demonstrated that zinc treatment prevents LPS-induced TNF-alpha expression and production in human monocytes by inhibiting cyclic nucleotide phosphodiesterase (PDE) activity and expression, and subsequent elevation of the cyclic nucleotide cGMP. In the present study, we investigated the molecular mechanism by which cGMP signaling affects the LPS-induced signaling cascade to suppress TNF-alpha transcription and release from monocytes. Zinc-mediated cGMP elevation led to cross activation of protein kinase A. This zinc-induced protein kinase A activation inhibited Raf-1 activity by phosphorylation at serine 259, preventing activation of Raf-1 by phosphorylation of serine 338. By this mechanism, zinc suppressed LPS-induced activation of IkappaB kinase beta (IKKbeta) and NF-kappaB, and subsequent TNF-alpha production. Our study shows that PDE inhibition by zinc modulates the monocytic immune response by selectively intervening in the Raf-1/IKKbeta/NF-kappaB pathway, which may constitute a common mechanism for the anti-inflammatory action of PDE inhibitors.
Collapse
Affiliation(s)
- Verena von Bülow
- Institute of Immunology, University Hospital, Rheinisch-Westfälische Technische Hochschule Aachen University, Aachen, Germany
| | | | | | | | | | | | | | | |
Collapse
|
46
|
Abstract
G proteins provide signal-coupling mechanisms to heptahelical cell surface receptors and are critically involved in the regulation of different mitogen-activated protein kinase (MAPK) networks. The four classes of G proteins, defined by the G(s), G(i), G(q) and G(12) families, regulate ERK1/2, JNK, p38MAPK, ERK5 and ERK6 modules by different mechanisms. The alpha- as well as betagamma-subunits are involved in the regulation of these MAPK modules in a context-specific manner. While the alpha- and betagamma-subunits primarily regulate the MAPK pathways via their respective effector-mediated signaling pathways, recent studies have unraveled several novel signaling intermediates including receptor tyrosine kinases and small GTPases through which these G-protein subunits positively as well as negatively regulate specific MAPK modules. Multiple mechanisms together with specific scaffold proteins that can link G-protein-coupled receptors or G proteins to distinct MAPK modules contribute to the context-specific and spatio-temporal regulation of mitogen-activated protein signaling networks by G proteins.
Collapse
Affiliation(s)
- Z G Goldsmith
- Fels Institute for Cancer Research and Molecular Biology, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | | |
Collapse
|
47
|
Schulte G, Levy FO. Novel aspects of G-protein-coupled receptor signalling--different ways to achieve specificity. Acta Physiol (Oxf) 2007; 190:33-8. [PMID: 17428230 DOI: 10.1111/j.1365-201x.2007.01696.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Our understanding of signal transduction via G-protein-coupled receptors (GPCR) has developed dramatically during the last decades. The initial idea of linear signalling pathways transferring information from the cell membrane to the nucleus has evolved into a complicated network of signalling pathways offering the possibility of crosstalk, fine tuning and specific regulation at multiple levels. During the recent meeting on GPCRs at the Karolinska Institutet, Stockholm novel aspects of GPCR signalling were presented and discussed. Here, we will discuss several possibilities for GPCRs to achieve specificity in signal transduction, such as the phenomenon of biased agonism, receptor multimerization, the role of co-receptors, the regulation of heterotrimeric G proteins as well as multiple G(s)-dependent pathways to extracellular single-regulated protein kinases.
Collapse
Affiliation(s)
- G Schulte
- Department of Physiology & Pharmacology, Karolinska Institutet, Stockholm, Sweden.
| | | |
Collapse
|
48
|
Rushworth LK, Hindley AD, O'Neill E, Kolch W. Regulation and role of Raf-1/B-Raf heterodimerization. Mol Cell Biol 2006; 26:2262-72. [PMID: 16508002 PMCID: PMC1430271 DOI: 10.1128/mcb.26.6.2262-2272.2006] [Citation(s) in RCA: 297] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Ras-Raf-MEK-extracellular signal-regulated kinase (ERK) pathway participates in the control of many fundamental cellular processes including proliferation, survival, and differentiation. The pathway is deregulated in up to 30% of human cancers, often due to mutations in Ras and the B-Raf isoform. Raf-1 and B-Raf can form heterodimers, and this may be important for cellular transformation. Here, we have analyzed the biochemical and biological properties of Raf-1/B-Raf heterodimers. Isolated Raf-1/B-Raf heterodimers possessed a highly increased kinase activity compared to the respective homodimers or monomers. Heterodimers between wild-type Raf-1 and B-Raf mutants with low or no kinase activity still displayed elevated kinase activity, as did heterodimers between wild-type B-Raf and kinase-negative Raf-1. In contrast, heterodimers containing both kinase-negative Raf-1 and kinase-negative B-Raf were completely inactive, suggesting that the kinase activity of the heterodimer specifically originates from Raf and that either kinase-competent Raf isoform is sufficient to confer high catalytic activity to the heterodimer. In cell lines, Raf-1/B-Raf heterodimers were found at low levels. Heterodimerization was enhanced by 14-3-3 proteins and by mitogens independently of ERK. However, ERK-induced phosphorylation of B-Raf on T753 promoted the disassembly of Raf heterodimers, and the mutation of T753 prolonged growth factor-induced heterodimerization. The B-Raf T753A mutant enhanced differentiation of PC12 cells, which was previously shown to be dependent on sustained ERK signaling. Fine mapping of the interaction sites by peptide arrays suggested a complex mode of interaction involving multiple contact sites with a main Raf-1 binding site in B-Raf encompassing T753. In summary, our data suggest that Raf-1/B-Raf heterodimerization occurs as part of the physiological activation process and that the heterodimer has distinct biochemical properties that may be important for the regulation of some biological processes.
Collapse
Affiliation(s)
- Linda K Rushworth
- Signalling and Proteomics Laboratory, Beatson Institute for Cancer Research, Garscube Estate, Glasgow G61 1BD, United Kingdom
| | | | | | | |
Collapse
|
49
|
Charest PG, Oligny-Longpré G, Bonin H, Azzi M, Bouvier M. The V2 vasopressin receptor stimulates ERK1/2 activity independently of heterotrimeric G protein signalling. Cell Signal 2006; 19:32-41. [PMID: 16857342 DOI: 10.1016/j.cellsig.2006.05.020] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2005] [Revised: 05/24/2006] [Accepted: 05/25/2006] [Indexed: 10/24/2022]
Abstract
The V2 vasopressin receptor (V2R) activates the mitogen activated protein kinases (MAPK) ERK1/2 through a mechanism involving the scaffolding protein beta arrestin. Here we report that this activating pathway is independent of G alpha s, G alpha i, G alpha q or G betagamma and that the V2R-mediated activation of G alpha s inhibits ERK1/2 activity in a cAMP/PKA-dependent manner. In the HEK293 cells studied, the beta arrestin-promoted activation was found to dominate over the PKA-mediated inhibition of the pathway, leading to a strong vasopressin-stimulated ERK1/2 activation. Despite the strong MAPK activation and in contrast with other GPCR, V2R did not induce any significant increase in DNA synthesis, consistent with the notion that the stable interaction between V2R and beta arrestin prevents signal propagation to the nucleus. Beta arrestin was found to be essential for the ERK1/2 activation, indicating that the recruitment of the scaffolding protein is necessary and sufficient to initiate the signal in the absence of any other stimulatory cues. Based on the use of selective pharmacological inhibitors, dominant negative mutants and siRNA, we conclude that the beta arrestin-dependent activation of ERK1/2 by the V2R involves c-Src and a metalloproteinase-dependent trans-activation event. These findings demonstrate that beta arrestin is a genuine signalling initiator that can, on its own, engage a MAPK activation machinery upon stimulation of a GPCR by its natural ligand.
Collapse
Affiliation(s)
- Pascale G Charest
- Department of Biochemistry and Groupe de Recherche Universitaire sur le Médicament, Institute for Research in Immunology and Cancer, Université de Montréal, C.P. 6128 Succursale Centre-Ville, Montréal (Québec) Canada H3C 3J7
| | | | | | | | | |
Collapse
|
50
|
Luft T, Rodionova E, Maraskovsky E, Kirsch M, Hess M, Buchholtz C, Goerner M, Schnurr M, Skoda R, Ho AD. Adaptive functional differentiation of dendritic cells: integrating the network of extra- and intracellular signals. Blood 2006; 107:4763-9. [PMID: 16527899 DOI: 10.1182/blood-2005-04-1501] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Phenotypic maturation, cytokine secretion, and migration are distinct functional characteristics of dendritic cells (DCs). These functions are independently regulated by a number of extracellular variables, such as type, strength, and persistence of an array of soluble and membrane-bound mediators. Since the exact composition of these variables in response to infection may differ between individuals, the intracellular signaling pathways activated by these extracellular networks may more closely correlate with DC function and predict the course of adaptive immunity. We found that activation of p38 kinase (p38K), extracellular signal-related kinase 1/2 (ERK1/2), and phosphatidylcholine-specific phospholipase C (PC-PLC) enhanced cytokine secretion, whereas p38K, cyclic adenosine monophosphate (cAMP), and PC-PLC enhanced migration. In contrast, phosphatidylinositol 3-kinase (PI3K)/Akt-1 and cAMP inhibited cytokine secretion while ERK1/2 inhibited migration. Migration and cytokine secretion further differed in their sensitivity to inhibition over time. However, although DCs could be manipulated to express migration, cytokine secretion, or both, the level of activation or persistence of intracellular pathway signaling was not predictive. Our results suggest a modular organization of function. We hypothesize that the expression of specific DC functions integrates a large variety of activating and inhibitory variables, and is represented by the formation of a functional unit of molecular networks-the signal response module (SRM). The combined activities of these modules define the functional outcome of DC activation.
Collapse
Affiliation(s)
- Thomas Luft
- The German Cancer Research Center, Dept of Molecular Oncology/Hematology, Heidelberg, Germany.
| | | | | | | | | | | | | | | | | | | |
Collapse
|