1
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Nobiletti N, Liu J, Glading AJ. KRIT1-mediated regulation of neutrophil adhesion and motility. FEBS J 2023; 290:1078-1095. [PMID: 36107440 PMCID: PMC9957810 DOI: 10.1111/febs.16627] [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: 04/18/2022] [Revised: 08/31/2022] [Accepted: 09/12/2022] [Indexed: 12/01/2022]
Abstract
Loss of Krev interaction-trapped-1 (KRIT1) expression leads to the development of cerebral cavernous malformations (CCM), a disease in which abnormal blood vessel formation compromises the structure and function of the blood-brain barrier. The role of KRIT1 in regulating endothelial function is well-established. However, several studies have suggested that KRIT1 could also play a role in regulating nonendothelial cell types and, in particular, immune cells. In this study, we generated a mouse model with neutrophil-specific deletion of KRIT1 in order to investigate the effect of KRIT1 deficiency on neutrophil function. Neutrophils isolated from adult Ly6Gtm2621(cre)Arte Krit1flox/flox mice had a reduced ability to attach and spread on the extracellular matrix protein fibronectin and exhibited a subsequent increase in migration. However, adhesion to and migration on ICAM-1 was unchanged. In addition, we used a monomeric, fluorescently-labelled fragment of fibronectin to show that integrin activation is reduced in the absence of KRIT1 expression, though β1 integrin expression appears unchanged. Finally, neutrophil migration in response to lipopolysaccharide-induced inflammation in the lung was decreased, as shown by reduced cell number and myeloperoxidase activity in lavage samples from Krit1PMNKO mice. Altogether, we show that KRIT1 regulates neutrophil adhesion and migration, likely through regulation of integrin activation, which can lead to altered inflammatory responses in vivo.
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Affiliation(s)
- Nicholas Nobiletti
- Department of Pharmacology and Physiology, School of Medicine and Dentistry, University of Rochester, NY, USA
| | - Jing Liu
- Department of Pharmacology and Physiology, School of Medicine and Dentistry, University of Rochester, NY, USA
- Department of Pediatrics, School of Medicine and Dentistry, University of Rochester, NY, USA
| | - Angela J. Glading
- Department of Pharmacology and Physiology, School of Medicine and Dentistry, University of Rochester, NY, USA
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2
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Char R, Pierre P. The RUFYs, a Family of Effector Proteins Involved in Intracellular Trafficking and Cytoskeleton Dynamics. Front Cell Dev Biol 2020; 8:779. [PMID: 32850870 PMCID: PMC7431699 DOI: 10.3389/fcell.2020.00779] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Accepted: 07/24/2020] [Indexed: 12/12/2022] Open
Abstract
Intracellular trafficking is essential for cell structure and function. In order to perform key tasks such as phagocytosis, secretion or migration, cells must coordinate their intracellular trafficking, and cytoskeleton dynamics. This relies on certain classes of proteins endowed with specialized and conserved domains that bridge membranes with effector proteins. Of particular interest are proteins capable of interacting with membrane subdomains enriched in specific phosphatidylinositol lipids, tightly regulated by various kinases and phosphatases. Here, we focus on the poorly studied RUFY family of adaptor proteins, characterized by a RUN domain, which interacts with small GTP-binding proteins, and a FYVE domain, involved in the recognition of phosphatidylinositol 3-phosphate. We report recent findings on this protein family that regulates endosomal trafficking, cell migration and upon dysfunction, can lead to severe pathology at the organismal level.
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Affiliation(s)
- Rémy Char
- Aix Marseille Université, Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, Centre d'Immunologie de Marseille-Luminy, Marseille, France
| | - Philippe Pierre
- Aix Marseille Université, Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, Centre d'Immunologie de Marseille-Luminy, Marseille, France.,Institute for Research in Biomedicine and Ilidio Pinho Foundation, Department of Medical Sciences, University of Aveiro, Aveiro, Portugal.,Shanghai Institute of Immunology, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
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3
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Zinatizadeh MR, Momeni SA, Zarandi PK, Chalbatani GM, Dana H, Mirzaei HR, Akbari ME, Miri SR. The Role and Function of Ras-association domain family in Cancer: A Review. Genes Dis 2019; 6:378-384. [PMID: 31832517 PMCID: PMC6889020 DOI: 10.1016/j.gendis.2019.07.008] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2019] [Revised: 07/16/2019] [Accepted: 07/18/2019] [Indexed: 02/08/2023] Open
Abstract
Ras gene mutation has been observed in more than 30% of cancers, and 90% of pancreatic, lung and colon cancers. Ras proteins (K-Ras, H-Ras, N-Ras) act as molecular switches which are activated by binding to GTP. They play a role in the cascade of cell process control (proliferation and cell division). In the inactive state, transforming GTP to GDP leads to the activation of GTpase in Ras gene. However, the mutation in Ras leads to the loss of internal GTPase activity and permanent activation of the protein. The activated Ras can promote the cell death or stop cell growth, which are facilitated by Ras-association domain family. Various studies have been conducted to determine the importance of losing RASSF proteins in Ras-induced tumors. This paper examines the role of Ras and RASSF proteins. In general, RASSF proteins can be used as a suitable means for targeting a large group of Ras-induced tumors.
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Affiliation(s)
- Mohammad Reza Zinatizadeh
- Cancer Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.,Cancer Research Center, Cancer Institute of Iran, Tehran University of Medical Science, Tehran, Iran
| | - Seyed Ali Momeni
- Uro-Oncology Research Center, Tehran University of Medical Sciences, Tehran, IR, Iran
| | - Peyman Kheirandish Zarandi
- Cancer Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.,Cancer Research Center, Cancer Institute of Iran, Tehran University of Medical Science, Tehran, Iran
| | | | - Hassan Dana
- Cancer Research Center, Cancer Institute of Iran, Tehran University of Medical Science, Tehran, Iran
| | - Hamid Reza Mirzaei
- Cancer Research Center, Shohadae Tajrish Hospital, Department of Radiation Oncology, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | | | - Seyed Rouhollah Miri
- Cancer Research Center, Cancer Institute of Iran, Tehran University of Medical Science, Tehran, Iran
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4
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Wang JC, Lee JYJ, Dang-Lawson M, Pritchard C, Gold MR. The Rap2c GTPase facilitates B cell receptor-induced reorientation of the microtubule-organizing center. Small GTPases 2018; 11:402-412. [PMID: 29457987 DOI: 10.1080/21541248.2018.1441626] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
When B lymphocytes encounter antigen-bearing surfaces, B-cell receptor (BCR) signaling initiates remodeling of the F-actin network and reorientation of the microtubule-organizing center (MTOC) towards the antigen contact site. We have previously shown that the Rap1 GTPase, an evolutionarily conserved regulator of cell polarity, is essential for these processes and that Rap1-regulated actin remodeling is required for MTOC polarization. The role of Rap2 proteins in establishing cell polarity is not well understood. We now show that depleting Rap2c, the only Rap2 isoform expressed in the A20 B-cell line, impairs BCR-induced MTOC reorientation as well as the actin remodeling that supports MTOC polarization. Thus Rap1 and Rap2 proteins may have similar but non-redundant functions in coupling the BCR to MTOC polarization.
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Affiliation(s)
- Jia C Wang
- Department of Microbiology & Immunology and the Life Sciences Institute, University of British Columbia , Vancouver, BC, Canada
| | - Jeff Y-J Lee
- Department of Microbiology & Immunology and the Life Sciences Institute, University of British Columbia , Vancouver, BC, Canada
| | - May Dang-Lawson
- Department of Microbiology & Immunology and the Life Sciences Institute, University of British Columbia , Vancouver, BC, Canada
| | - Caitlin Pritchard
- Department of Microbiology & Immunology and the Life Sciences Institute, University of British Columbia , Vancouver, BC, Canada
| | - Michael R Gold
- Department of Microbiology & Immunology and the Life Sciences Institute, University of British Columbia , Vancouver, BC, Canada
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5
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Margineanu A, Chan JJ, Kelly DJ, Warren SC, Flatters D, Kumar S, Katan M, Dunsby CW, French PMW. Screening for protein-protein interactions using Förster resonance energy transfer (FRET) and fluorescence lifetime imaging microscopy (FLIM). Sci Rep 2016; 6:28186. [PMID: 27339025 PMCID: PMC4919659 DOI: 10.1038/srep28186] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2016] [Accepted: 05/19/2016] [Indexed: 11/09/2022] Open
Abstract
We present a high content multiwell plate cell-based assay approach to quantify protein interactions directly in cells using Förster resonance energy transfer (FRET) read out by automated fluorescence lifetime imaging (FLIM). Automated FLIM is implemented using wide-field time-gated detection, typically requiring only 10 s per field of view (FOV). Averaging over biological, thermal and shot noise with 100's to 1000's of FOV enables unbiased quantitative analysis with high statistical power. Plotting average donor lifetime vs. acceptor/donor intensity ratio clearly identifies protein interactions and fitting to double exponential donor decay models provides estimates of interacting population fractions that, with calibrated donor and acceptor fluorescence intensities, can yield dissociation constants. We demonstrate the application to identify binding partners of MST1 kinase and estimate interaction strength among the members of the RASSF protein family, which have important roles in apoptosis via the Hippo signalling pathway. KD values broadly agree with published biochemical measurements.
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Affiliation(s)
- Anca Margineanu
- Imperial College London, Dept. Physics, Photonics Lab., Blackett building, Prince Consort Road, London, SW7 2AZ, UK
| | - Jia Jia Chan
- University College London, Institute of Structural and Molecular Biology, Darwin building, Gower St., London, WC1E 6BT, UK
| | - Douglas J. Kelly
- Imperial College London, Dept. Physics, Photonics Lab., Blackett building, Prince Consort Road, London, SW7 2AZ, UK
- Imperial College London, Institute of Chemical Biology, London, SW7 2AZ, London, UK
| | - Sean C. Warren
- Imperial College London, Dept. Physics, Photonics Lab., Blackett building, Prince Consort Road, London, SW7 2AZ, UK
- Imperial College London, Institute of Chemical Biology, London, SW7 2AZ, London, UK
| | - Delphine Flatters
- Université Paris Diderot, Sorbonne Paris Cité, Molécules Thérapeutiques in silico, Inserm UMR-S 973, 35 rue Helene Brion, 75013 Paris, France
| | - Sunil Kumar
- Imperial College London, Dept. Physics, Photonics Lab., Blackett building, Prince Consort Road, London, SW7 2AZ, UK
| | - Matilda Katan
- University College London, Institute of Structural and Molecular Biology, Darwin building, Gower St., London, WC1E 6BT, UK
| | - Christopher W. Dunsby
- Imperial College London, Dept. Physics, Photonics Lab., Blackett building, Prince Consort Road, London, SW7 2AZ, UK
| | - Paul M. W. French
- Imperial College London, Dept. Physics, Photonics Lab., Blackett building, Prince Consort Road, London, SW7 2AZ, UK
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6
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Zhu Z, Di J, Lu Z, Gao K, Zheng J. Rap2B GTPase: structure, functions, and regulation. Tumour Biol 2016; 37:7085-93. [PMID: 27012552 DOI: 10.1007/s13277-016-5033-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Accepted: 03/18/2016] [Indexed: 02/08/2023] Open
Abstract
Rap2B GTPase, a member of Ras-related protein superfamily, was first discovered from a platelet cDNA library in the early 1990s. Since then, it has been reported to play an important role in regulating cellular processes including cytoskeletal organization, cell growth, and proliferation. It can be stimulated and suppressed by a wide range of external and internal inducers, circulating between GTP-bound active state and GDP-bound inactive state. Increasing focus on Ras signaling pathway reveals critical effects of Rap2B on tumorigenesis. In particular, Rap2B behaves in a p53-dependent manner in regulation of apoptosis and migration. Apart from being an oncogenic activator, Rap2B has been found to participate in many other physiological events via diverse downstream effectors. In this review, we present recent studies on the structure, regulation, and multiple biological functions of Rap2B, shedding light on its potential status in treatment of cancer as well as other diseases.
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Affiliation(s)
- Zhesi Zhu
- Cancer Institute, Xuzhou Medical College, Xuzhou, 221002, Jiangsu, People's Republic of China
| | - Jiehui Di
- Cancer Institute, Xuzhou Medical College, Xuzhou, 221002, Jiangsu, People's Republic of China.,Department of Radiation Oncology and Lineberger Comprehensive Cancer Center, School of Medicine, The University of North Carolina at Chapel Hill, 101 Manning Drive, Chapel Hill, NC, 27514, USA
| | - Zheng Lu
- Cancer Institute, Xuzhou Medical College, Xuzhou, 221002, Jiangsu, People's Republic of China
| | - Keyu Gao
- Cancer Institute, Xuzhou Medical College, Xuzhou, 221002, Jiangsu, People's Republic of China
| | - Junnian Zheng
- Jiangsu Center for the Collaboration and Innovation of Cancer Biotherapy, Cancer Institute, Xuzhou Medical College, Xuzhou, 221002, Jiangsu, People's Republic of China. .,Center of Clinical Oncology, Affiliated Hospital of Xuzhou Medical College, Xuzhou, China.
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7
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Di J, Huang H, Wang Y, Qu D, Tang J, Cheng Q, Lu Z, Zhang Y, Zheng J. p53 target gene Rap2B regulates the cytoskeleton and inhibits cell spreading. J Cancer Res Clin Oncol 2015; 141:1791-8. [PMID: 25762091 DOI: 10.1007/s00432-015-1948-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2014] [Accepted: 02/23/2015] [Indexed: 11/28/2022]
Abstract
PURPOSE Cell migration requires spatiotemporal integration of signals that target cytoskeletal. Previous studies have indicated that Rho GTPases are crucial regulators of actin dynamics. As homologs of Rho proteins, the role of Rap2B in the regulation of cytoskeleton and its cell signaling pathway remains unknown. METHODS The cellular functions of Rap2B were monitored by Western blotting and immunofluorescence staining in order to characterize the protein level and the cell shape. RESULTS Here, we show that expression of Rap2B was induced by nocodazole in a p53-dependent manner. However, Rap2B itself is not necessary for p53-dependent cell cycle arrest. We evidenced that over-expression of Rap2B may inhibit cell spreading by disrupting actin dynamics upon nocodazole treatment, but Rap2B (C180A) mutant does not. In contrast, knockdown of Rap2B promoted cell spreading. CONCLUSIONS Altogether, these results revealed that Rap2B plays a pivotal role in cytoskeleton reorganization and subsequently inhibits cell spreading, which could be responsible for cancer metastasis.
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Affiliation(s)
- Jiehui Di
- Cancer Institute, Xuzhou Medical College, Xuzhou, 221002, Jiangsu, China
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8
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Moving towards a paradigm: common mechanisms of chemotactic signaling in Dictyostelium and mammalian leukocytes. Cell Mol Life Sci 2014; 71:3711-47. [PMID: 24846395 DOI: 10.1007/s00018-014-1638-8] [Citation(s) in RCA: 154] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Revised: 04/24/2014] [Accepted: 04/29/2014] [Indexed: 12/31/2022]
Abstract
Chemotaxis, or directed migration of cells along a chemical gradient, is a highly coordinated process that involves gradient sensing, motility, and polarity. Most of our understanding of chemotaxis comes from studies of cells undergoing amoeboid-type migration, in particular the social amoeba Dictyostelium discoideum and leukocytes. In these amoeboid cells the molecular events leading to directed migration can be conceptually divided into four interacting networks: receptor/G protein, signal transduction, cytoskeleton, and polarity. The signal transduction network occupies a central position in this scheme as it receives direct input from the receptor/G protein network, as well as feedback from the cytoskeletal and polarity networks. Multiple overlapping modules within the signal transduction network transmit the signals to the actin cytoskeleton network leading to biased pseudopod protrusion in the direction of the gradient. The overall architecture of the networks, as well as the individual signaling modules, is remarkably conserved between Dictyostelium and mammalian leukocytes, and the similarities and differences between the two systems are the subject of this review.
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9
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Volodko N, Gordon M, Salla M, Ghazaleh HA, Baksh S. RASSF tumor suppressor gene family: Biological functions and regulation. FEBS Lett 2014; 588:2671-84. [DOI: 10.1016/j.febslet.2014.02.041] [Citation(s) in RCA: 92] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2014] [Revised: 02/25/2014] [Accepted: 02/25/2014] [Indexed: 01/22/2023]
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10
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Chan JJ, Katan M. PLCɛ and the RASSF family in tumour suppression and other functions. Adv Biol Regul 2013; 53:258-279. [PMID: 23958207 DOI: 10.1016/j.jbior.2013.07.008] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2013] [Accepted: 07/15/2013] [Indexed: 06/02/2023]
Abstract
Not all proteins implicated in direct binding to Ras appear to have a positive role in the generation and progression of tumours; examples include Phospholipase C epsilon (PLCɛ) and some members of the Ras-association domain family (RASSF). The RASSF family comprises of ten members, known as RASSF1 to RASSF10. PLCɛ and RASSF members carry a common Ras-association domain (RA) that can potentially bind Ras oncoproteins and mediate Ras-regulated functions. RASSF1 to RASSF6 also share a common SARAH domain that facilitates protein-protein interactions with other SARAH domain proteins. The majority of the family are frequently downregulated by epigenetic silencing in cancers. They are implicated in various important biological processes including apoptosis, microtubule stabilisation and cell cycle regulation. Recent studies have reinforced the tumour suppressive properties of the RASSF family, with new evidence of emerging pathways and novel functions that suggest a wider role for these proteins. This review will first describe an emerging role of PLCɛ in tumour suppression and then focus on and summarise the new findings on the RASSF family in the last five years to consolidate their well-established functions, and highlight the new regulatory roles of specific RASSF members.
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Affiliation(s)
- Jia Jia Chan
- Institute of Structural and Molecular Biology, Division of Biosciences, University College London, Gower Street, London WC1E 6BT, UK
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11
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Pye DS, Rubio I, Pusch R, Lin K, Pettitt AR, Till KJ. Chemokine unresponsiveness of chronic lymphocytic leukemia cells results from impaired endosomal recycling of Rap1 and is associated with a distinctive type of immunological anergy. THE JOURNAL OF IMMUNOLOGY 2013; 191:1496-504. [PMID: 23804711 DOI: 10.4049/jimmunol.1203484] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Trafficking of malignant lymphocytes is fundamental to the biology of chronic lymphocytic leukemia (CLL). Transendothelial migration (TEM) of normal lymphocytes into lymph nodes requires the chemokine-induced activation of Rap1 and αLβ2 integrin. However, in most cases of CLL, Rap1 is refractory to chemokine stimulation, resulting in failed αLβ2 activation and TEM unless α4β1 is coexpressed. In this study, we show that the inability of CXCL12 to induce Rap1 GTP loading in CLL cells results from failure of Rap1-containing endosomes to translocate to the plasma membrane. Furthermore, failure of chemokine-induced Rap1 translocation/GTP loading was associated with a specific pattern of cellular IgD distribution resembling that observed in normal B cells anergized by DNA-based Ags. Anergic features and chemokine unresponsiveness could be simultaneously reversed by culturing CLL cells ex vivo, suggesting that these two features are coupled and driven by stimuli present in the in vivo microenvironment. Finally, we show that failure of Rap1 translocation/GTP loading is linked to defective activation of phospholipase D1 and its upstream activator Arf1. Taken together, our findings indicate that chemokine unresponsiveness in CLL lymphocytes results from failure of Arf1/phospholipase D1-mediated translocation of Rap1 to the plasma membrane for GTP loading and may be a specific feature of anergy induced by DNA Ags.
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Affiliation(s)
- Derek S Pye
- Department of Molecular and Clinical Cancer Medicine, University of Liverpool, Liverpool L69 3GA, United Kingdom
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12
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Chan JJ, Flatters D, Rodrigues-Lima F, Yan J, Thalassinos K, Katan M. Comparative analysis of interactions of RASSF1-10. Adv Biol Regul 2013; 53:190-201. [PMID: 23357313 PMCID: PMC4221134 DOI: 10.1016/j.jbior.2012.12.001] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Accepted: 12/13/2012] [Indexed: 01/01/2023]
Abstract
Members of the RASSF family (RASSF1-10) have been identified as candidate tumour suppressors that are frequently downregulated by promoter hypermethylation in cancers. These proteins carry a common Ras-association (RA) and SARAH domain (RASSF1-6) that can potentially bind Ras oncoproteins and mediate protein-protein interactions with other SARAH domain proteins. However, there is a notable lack of comparative characterisation of the RASSF family, as well as molecular and structural information that facilitate their tumour suppressive functions. As part of our comparative analysis, we modelled the RA and SARAH domains of the RASSF members based on existing structures and predicted their potential interactions. These in silico predictions were compared to in vitro interaction studies with Ras and MST kinase (a SARAH domain-containing protein). Our data shows a diversity of interaction within the RASSF family RA domain, whereas the SARAH domain-mediated interactions for RASSF1-6 are consistent with the predictions. This suggests that different members, despite shared general architecture, could have distinct functional properties. Additionally, we identify a new interacting partner for MST kinase in the form of RASSF7. Current data supports an interaction model where RASSF serves as an adaptor for the assembly of multiple protein complexes and further functional interactions, involving MST kinases and other SARAH domain proteins, which could be regulated by Ras.
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Affiliation(s)
- Jia Jia Chan
- Institute of Structural and Molecular Biology, Division of Biosciences, University College London, Gower Street, London WC1E 6BT, UK
| | - Delphine Flatters
- Université Paris Diderot, Sorbonne Paris Cité, Molécules Thérapeutiques in silico, Inserm UMR-S 973, 35 rue Helene Brion, 75013 Paris, France
| | - Fernando Rodrigues-Lima
- Université Paris Diderot, Sorbonne Paris Cité, Unité de Biologie Fonctionnelle et Adaptative, CNRS EAC4413, 75013, Paris, France
| | - Jun Yan
- Institute of Structural and Molecular Biology, Division of Biosciences, University College London, Gower Street, London WC1E 6BT, UK
| | - Konstantinos Thalassinos
- Institute of Structural and Molecular Biology, Division of Biosciences, University College London, Gower Street, London WC1E 6BT, UK
| | - Matilda Katan
- Institute of Structural and Molecular Biology, Division of Biosciences, University College London, Gower Street, London WC1E 6BT, UK
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13
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Lu Z, Bast RC. The tumor suppressor gene ARHI (DIRAS3) inhibits ovarian cancer cell migration through multiple mechanisms. Cell Adh Migr 2013; 7:232-6. [PMID: 23357870 DOI: 10.4161/cam.23648] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
ARHI is an imprinted tumor suppressor gene that is downregulated in > 60% of ovarian cancers, associated with decreased progression-free survival. ARHI encodes a 26 kDa GTPase with homology to Ras. Re-expression of ARHI inhibits ovarian cancer growth, initiates autophagy and induces tumor dormancy. Recent studies have demonstrated that ARHI also plays a particularly important role in ovarian cancer cell migration. Re-expression of ARHI decreases motility of IL-6- and EGF-stimulated SKOv3 and Hey ovarian cancer cells, inhibiting both chemotaxis and haptotaxis. ARHI inhibits cell migration by binding and sequestering STAT3 in the cytoplasm, and preventing STAT3 translocation to the nucleus and localization in focal adhesion complexes. Re-expression of ARHI inhibits FAK (Y397) phosphorylation, disrupts focal adhesions and blocks FAK-mediated RhoA signaling, resulting in decreased levels of GTP-RhoA. Re-expression of ARHI disrupts formation of actin stress fibers in a FAK- and RhoA-dependent manner. Recent studies indicate that re-expression of ARHI inhibits expression of β-1 integrin which may also contribute to inhibition of migration, adhesion and invasion.
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Affiliation(s)
- Zhen Lu
- Department of Experimental Therapeutics, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
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14
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Stanley P, Tooze S, Hogg N. A role for Rap2 in recycling the extended conformation of LFA-1 during T cell migration. Biol Open 2012; 1:1161-8. [PMID: 23213397 PMCID: PMC3507183 DOI: 10.1242/bio.20122824] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2012] [Accepted: 08/29/2012] [Indexed: 01/07/2023] Open
Abstract
T lymphocytes make use of their major integrin LFA-1 to migrate on surfaces that express ICAM-1 such as blood vessels and inflamed tissue sites. How the adhesions are turned over in order to supply traction for this migration has not been extensively investigated. By following the fate of biotinylated membrane LFA-1 on T lymphocytes, we show in this study that LFA-1 internalization and re-exposure on the plasma membrane are linked to migration. Previously we demonstrated the GTPase Rap2 to be a regulator of LFA-1-mediated migration. SiRNA knockdown of this GTPase inhibits both LFA-1 internalization and also its ability to be re-exposed, indicating that Rap2 participates in recycling of LFA-1 and influences its complete endocytosis-exocytosis cycle. Confocal microscopy images reveal that the intracellular distribution of Rap2 overlaps with endosomal recycling vesicles. Although the homologous GTPase Rap1 is also found on intracellular vesicles and associated with LFA-1 activation, these two homologous GTPases do not co-localize. Little is known about the conformation of the LFA-1 that is recycled. We show that the extended form of LFA-1 is internalized and in Rap2 siRNA-treated T lymphocytes the trafficking of this LFA-1 conformation is disrupted resulting in its intracellular accumulation. Thus LFA-1-mediated migration of T lymphocytes requires Rap2-expressing vesicles to recycle the extended form of LFA-1 that we have previously found to control migration at the leading edge.
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Affiliation(s)
- Paula Stanley
- Leukocyte Adhesion Laboratory, Cancer Research UK, London Research InstituteLondon EC1V 4AD, UK
| | - Sharon Tooze
- Secretory Pathways Laboratory, Cancer Research UK, London Research InstituteLondon EC1V 4AD, UK
| | - Nancy Hogg
- Leukocyte Adhesion Laboratory, Cancer Research UK, London Research InstituteLondon EC1V 4AD, UK
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15
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The leucocyte β2 (CD18) integrins: the structure, functional regulation and signalling properties. Biosci Rep 2012; 32:241-69. [PMID: 22458844 DOI: 10.1042/bsr20110101] [Citation(s) in RCA: 126] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Leucocytes are highly motile cells. Their ability to migrate into tissues and organs is dependent on cell adhesion molecules. The integrins are a family of heterodimeric transmembrane cell adhesion molecules that are also signalling receptors. They are involved in many biological processes, including the development of metazoans, immunity, haemostasis, wound healing and cell survival, proliferation and differentiation. The leucocyte-restricted β2 integrins comprise four members, namely αLβ2, αMβ2, αXβ2 and αDβ2, which are required for a functional immune system. In this paper, the structure, functional regulation and signalling properties of these integrins are reviewed.
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16
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Wernimont SA, Wiemer AJ, Bennin DA, Monkley SJ, Ludwig T, Critchley DR, Huttenlocher A. Contact-dependent T cell activation and T cell stopping require talin1. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2011; 187:6256-67. [PMID: 22075696 PMCID: PMC3237745 DOI: 10.4049/jimmunol.1102028] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
T cell-APC contact initiates T cell activation and is maintained by the integrin LFA-1. Talin1, an LFA-1 regulator, localizes to the immune synapse (IS) with unknown roles in T cell activation. In this study, we show that talin1-deficient T cells have defects in contact-dependent T cell stopping and proliferation. Although talin1-deficient T cells did not form stable interactions with APCs, transient contacts were sufficient to induce signaling. In contrast to prior models, LFA-1 polarized to T cell-APC contacts in talin1-deficient T cells, but vinculin and F-actin polarization at the IS was impaired. These results indicate that T cell proliferation requires sustained, talin1-mediated T cell-APC interactions and that talin1 is necessary for F-actin polarization and the stability of the IS.
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Affiliation(s)
- Sarah A Wernimont
- Program in Cellular and Molecular Biology, University of Wisconsin, Madison WI 53705
| | - Andrew J Wiemer
- Department of Pediatrics and Medical Microbiology and Immunology, University of Wisconsin, Madison WI 53706
- Institute on Aging, University of Wisconsin-Madison, Madison WI 53706
| | - David A Bennin
- Department of Pediatrics and Medical Microbiology and Immunology, University of Wisconsin, Madison WI 53706
| | - Susan J Monkley
- Department of Biochemistry, University of Leicester, Leicester LE1 9HN, UK
| | - Thomas Ludwig
- Institute for Cancer Genetics, Columbia University, New York, NY 10032
| | - David R Critchley
- Department of Biochemistry, University of Leicester, Leicester LE1 9HN, UK
| | - Anna Huttenlocher
- Department of Pediatrics and Medical Microbiology and Immunology, University of Wisconsin, Madison WI 53706
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17
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Yoshida H, Kitagishi Y, Okumura N, Murakami M, Nishimura Y, Matsuda S. How do you RUN on? FEBS Lett 2011; 585:1707-10. [PMID: 21570977 DOI: 10.1016/j.febslet.2011.05.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2011] [Revised: 05/03/2011] [Accepted: 05/03/2011] [Indexed: 10/18/2022]
Abstract
RUN domain is present in several proteins related to the functions of Rap and Rab family GTPases. Accumulating evidence supports the hypothesis that RUN domain-containing proteins act as a component of vesicle traffic and might be responsible for an interaction with a filamentous network linked to actin cytoskeleton or microtubules. That is to say, on one hand, RUN domains associate with Rab or Rap family proteins, on the other hand, they also might interact with motor proteins such as kinesin or myosin via intervention molecules. In this review, we summarize the background and current status of RUN domain research with an emphasis on the interaction between RUN domain and motor proteins with respect to the vesicle traffic on filamentous network.
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Affiliation(s)
- Hitomi Yoshida
- Department of Environmental Health Science, Nara Women's University, Kita-Uoya Nishimachi, Nara, Japan
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18
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Ross SH, Post A, Raaijmakers JH, Verlaan I, Gloerich M, Bos JL. Ezrin is required for efficient Rap1-induced cell spreading. J Cell Sci 2011; 124:1808-18. [PMID: 21540295 DOI: 10.1242/jcs.079830] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Rap family of small GTPases regulate the adhesion of cells to extracellular matrices. Several Rap-binding proteins have been shown to function as effectors that mediate Rap-induced adhesion. However, little is known regarding the relationships between these effectors, or about other proteins that are downstream of or act in parallel to the effectors. To establish whether an array of effectors was required for Rap-induced cell adhesion and spreading, and to find new components involved in Rap-signal transduction, we performed a small-scale siRNA screen in A549 lung epithelial cells. Of the Rap effectors tested, only Radil blocked Rap-induced spreading. Additionally, we identified a novel role for Ezrin downstream of Rap1. Ezrin was necessary for Rap-induced cell spreading, but not Rap-induced cell adhesion or basal adhesion processes. Furthermore, Ezrin depletion inhibited Rap-induced cell spreading in several cell lines, including primary human umbilical vein endothelial cells. Interestingly, Radixin and Moesin, two proteins with high homology to Ezrin, are not required for Rap-induced cell spreading and cannot compensate for loss of Ezrin to rescue Rap-induced cell spreading. Here, we present a novel function for Ezrin in Rap1-induced cell spreading and evidence of a non-redundant role of an ERM family member.
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Affiliation(s)
- Sarah H Ross
- Molecular Cancer Research, Centre for Biomedical Genetics and Cancer Genomics Centre, University Medical Centre Utrecht, 3584 CG Utrecht, The Netherlands.
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19
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Lin KBL, Freeman SA, Gold MR. Rap GTPase-mediated adhesion and migration: A target for limiting the dissemination of B-cell lymphomas? Cell Adh Migr 2010; 4:327-32. [PMID: 20212359 DOI: 10.4161/cam.4.3.11114] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
B-cell lymphomas, which arise in lymphoid organs, can spread rapidly via the circulatory system and form solid tumors within multiple organs. Rate-limiting steps in this metastatic process may be the adhesion of lymphoma cells to vascular endothelial cells, their exit from the vasculature and their migration to tissue sites that will support tumor growth. Thus proteins that control B cell adhesion and migration are likely to be key factors in lymphoma dissemination, and hence potential targets for therapeutic intervention. The Rap GTPases are master regulators of integrin activation, cell motility and the underlying cytoskeletal, adhesion and membrane dynamics. We have recently shown that Rap activation is critical for B-lymphoma cells to undergo transendothelial migration in vitro and in vivo. As a consequence, suppressing Rap activation impairs the ability of intravenously injected B-lymphoma cells to form solid tumors in the liver and other organs. We discuss this work in the context of targeting Rap, its downstream effectors, or other regulators of B cell adhesion and migration as an approach for limiting the dissemination of B-lymphoma cells and the development of secondary tumors.
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Affiliation(s)
- Kevin B L Lin
- Department of Microbiology and Immunology and Life Sciences Institute I3 and CELL research groups, University of British Columbia, Vancouver, BC, Canada
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20
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Richter AM, Pfeifer GP, Dammann RH. The RASSF proteins in cancer; from epigenetic silencing to functional characterization. Biochim Biophys Acta Rev Cancer 2009; 1796:114-28. [DOI: 10.1016/j.bbcan.2009.03.004] [Citation(s) in RCA: 161] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2008] [Revised: 03/19/2009] [Accepted: 03/21/2009] [Indexed: 01/22/2023]
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21
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Rap1 controls lymphocyte adhesion cascade and interstitial migration within lymph nodes in RAPL-dependent and -independent manners. Blood 2009; 115:804-14. [PMID: 19965628 DOI: 10.1182/blood-2009-03-211979] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The small GTPase Rap1 and its effector RAPL regulate lymphocyte adhesion and motility. However, their precise regulatory roles in the adhesion cascade preceding entry into lymph nodes and during interstitial migration are unclear. Here, we show that Rap1 is indispensably required for the chemokine-triggered initial arrest step of rolling lymphocytes through LFA-1, whereas RAPL is not involved in rapid arrest. RAPL and talin play a critical role in stabilizing lymphocyte arrest to the endothelium of blood vessels under flow or to the high endothelial venules of peripheral lymph nodes in vivo. Further, mutagenesis and peptide studies suggest that release of a trans-acting restraint from the beta2 cytoplasmic region of LFA-1 is critical for Rap1-dependent initial arrest. Rap1 or RAPL deficiency severely impaired lymphocyte motility over lymph node stromal cells in vitro, and RAPL deficiency impaired high-velocity directional movement within lymph nodes. These findings reveal the several critical steps of Rap1, which are RAPL-dependent and -independent, in lymphocyte trafficking.
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22
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Horn J, Wang X, Reichardt P, Stradal TE, Warnecke N, Simeoni L, Gunzer M, Yablonski D, Schraven B, Kliche S. Src homology 2-domain containing leukocyte-specific phosphoprotein of 76 kDa is mandatory for TCR-mediated inside-out signaling, but dispensable for CXCR4-mediated LFA-1 activation, adhesion, and migration of T cells. THE JOURNAL OF IMMUNOLOGY 2009; 183:5756-67. [PMID: 19812192 DOI: 10.4049/jimmunol.0900649] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Engagement of the TCR or of chemokine receptors such as CXCR4 induces adhesion and migration of T cells via so-called inside-out signaling pathways. The molecular processes underlying inside-out signaling events are as yet not completely understood. In this study, we show that TCR- and CXCR4-mediated activation of integrins critically depends on the membrane recruitment of the adhesion- and degranulation-promoting adapter protein (ADAP)/Src kinase-associated phosphoprotein of 55 kDa (SKAP55)/Rap1-interacting adapter protein (RIAM)/Rap1 module. We further demonstrate that the Src homology 2 domain containing leukocyte-specific phosphoprotein of 76 kDa (SLP76) is crucial for TCR-mediated inside-out signaling and T cell/APC interaction. Besides facilitating membrane recruitment of ADAP, SKAP55, and RIAM, SLP76 regulates TCR-mediated inside-out signaling by controlling the activation of Rap1 as well as Rac-mediated actin polymerization. Surprisingly, however, SLP76 is not mandatory for CXCR4-mediated inside-out signaling. Indeed, both CXCR4-induced T cell adhesion and migration are not affected by loss of SLP76. Moreover, after CXCR4 stimulation, the ADAP/SKAP55/RIAM/Rap1 module is recruited to the plasma membrane independently of SLP76. Collectively, our data indicate a differential requirement for SLP76 in TCR- vs CXCR4-mediated inside-out signaling pathways regulating T cell adhesion and migration.
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Affiliation(s)
- Jessica Horn
- Institute of Molecular and Clinical Immunology, Otto-von-Guericke University, Magdeburg, Germany
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23
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Yaman E, Gasper R, Koerner C, Wittinghofer A, Tazebay UH. RasGEF1A and RasGEF1B are guanine nucleotide exchange factors that discriminate between Rap GTP-binding proteins and mediate Rap2-specific nucleotide exchange. FEBS J 2009; 276:4607-16. [DOI: 10.1111/j.1742-4658.2009.07166.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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24
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Avruch J, Xavier R, Bardeesy N, Zhang XF, Praskova M, Zhou D, Xia F. Rassf family of tumor suppressor polypeptides. J Biol Chem 2009; 284:11001-5. [PMID: 19091744 PMCID: PMC2670104 DOI: 10.1074/jbc.r800073200] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Rassf1-6 polypeptides each contain a Ras/Rap association domain, which enables binding to several GTP-charged Ras-like GTPases, at least in vitro or when overexpressed. The Ras/Rap association domains are followed by SARAH domains, which mediate Rassf heterodimerization with the Mst1/2 protein kinases. Rassf1A is unequivocally a tumor suppressor, and all Rassf proteins behave like tumor suppressors, exhibiting epigenetic silencing of expression in many human cancers and pro-apoptotic and/or anti-proliferative effects when re-expressed in tumor cell lines. Herein, we review the binding of the Rassf polypeptides to Ras-like GTPases and the Mst1/2 kinases and their role in Rassf function.
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Affiliation(s)
- Joseph Avruch
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA, USA.
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25
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Abstract
Ras and Rap proteins are closely related small GTPases. Whereas Ras is known for its role in cell proliferation and survival, Rap1 is predominantly involved in cell adhesion and cell junction formation. Ras and Rap are regulated by different sets of guanine nucleotide exchange factors and GTPase-activating proteins, determining one level of specificity. In addition, although the effector domains are highly similar, Rap and Ras interact with largely different sets of effectors, providing a second level of specificity. In this review, we discuss the regulatory proteins and effectors of Ras and Rap, with a focus on those of Rap.
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Affiliation(s)
- Judith H Raaijmakers
- Department of Physiological Chemistry, Centre for Biomedical Genetics, Universitair Medisch Centrum Utrecht, Universiteitsweg 100, 3584 CG Utrecht, The Netherlands
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26
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Bjelić S, Jelesarov I. A survey of the year 2007 literature on applications of isothermal titration calorimetry. J Mol Recognit 2008; 21:289-312. [PMID: 18729242 DOI: 10.1002/jmr.909] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Elucidation of the energetic principles of binding affinity and specificity is a central task in many branches of current sciences: biology, medicine, pharmacology, chemistry, material sciences, etc. In biomedical research, integral approaches combining structural information with in-solution biophysical data have proved to be a powerful way toward understanding the physical basis of vital cellular phenomena. Isothermal titration calorimetry (ITC) is a valuable experimental tool facilitating quantification of the thermodynamic parameters that characterize recognition processes involving biomacromolecules. The method provides access to all relevant thermodynamic information by performing a few experiments. In particular, ITC experiments allow to by-pass tedious and (rarely precise) procedures aimed at determining the changes in enthalpy and entropy upon binding by van't Hoff analysis. Notwithstanding limitations, ITC has now the reputation of being the "gold standard" and ITC data are widely used to validate theoretical predictions of thermodynamic parameters, as well as to benchmark the results of novel binding assays. In this paper, we discuss several publications from 2007 reporting ITC results. The focus is on applications in biologically oriented fields. We do not intend a comprehensive coverage of all newly accumulated information. Rather, we emphasize work which has captured our attention with originality and far-reaching analysis, or else has provided ideas for expanding the potential of the method.
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Affiliation(s)
- Sasa Bjelić
- Biochemisches Institut der Universität Zürich, Winterthurerstrasse 190, Zürich, Switzerland
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27
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Till KJ, Harris RJ, Linford A, Spiller DG, Zuzel M, Cawley JC. Cell motility in chronic lymphocytic leukemia: defective Rap1 and alphaLbeta2 activation by chemokine. Cancer Res 2008; 68:8429-36. [PMID: 18922916 DOI: 10.1158/0008-5472.can-08-1758] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Chemokine-induced activation of alpha4beta1 and alphaLbeta2 integrins (by conformational change and clustering) is required for lymphocyte transendothelial migration (TEM) and entry into lymph nodes. We have previously reported that chemokine-induced TEM is defective in chronic lymphocytic leukemia (CLL) and that this defect is a result of failure of the chemokine to induce polar clustering of alphaLbeta2; engagement of alpha4beta1 and autocrine vascular endothelial growth factor (VEGF) restore clustering and TEM. The aim of the present study was to characterize the nature of this defect in alphaLbeta2 activation and determine how it is corrected. We show here that the alphaLbeta2 of CLL cells is already in variably activated conformations, which are not further altered by chemokine treatment. Importantly, such treatment usually does not cause an increase in the GTP-loading of Rap1, a GTPase central to chemokine-induced activation of integrins. Furthermore, we show that this defect in Rap1 GTP-loading is at the level of the GTPase and is corrected in CLL cells cultured in the absence of exogenous stimuli, suggesting that the defect is the result of in vivo stimulation. Finally, we show that, because Rap1-induced activation of both alpha4beta1 and alphaLbeta2 is defective, autocrine VEGF and chemokine are necessary to activate alpha4beta1 for ligand binding. Subsequently, this binding and both VEGF and chemokine stimulation are all needed for alphaLbeta2 activation for motility and TEM. The present study not only clarifies the nature of the alphaLbeta2 defect of CLL cells but is the first to implicate activation of Rap1 in the pathophysiology of CLL.
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Affiliation(s)
- Kathleen J Till
- Division of Hematology, School of Cancer Studies, School of Biological Sciences, University of Liverpool, Liverpool, United Kingdom.
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28
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Rich RL, Myszka DG. Survey of the year 2007 commercial optical biosensor literature. J Mol Recognit 2008; 21:355-400. [DOI: 10.1002/jmr.928] [Citation(s) in RCA: 144] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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29
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Chu H, Awasthi A, White GC, Chrzanowska-Wodnicka M, Malarkannan S. Rap1b regulates B cell development, homing, and T cell-dependent humoral immunity. THE JOURNAL OF IMMUNOLOGY 2008; 181:3373-83. [PMID: 18714009 DOI: 10.4049/jimmunol.181.5.3373] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Rap1 is a small GTPase that belongs to Ras superfamily. This ubiquitously expressed GTPase is a key regulator of integrin functions. Rap1 exists in two isoforms: Rap1a and Rap1b. Although Rap1 has been extensively studied, its isoform-specific functions in B cells have not been elucidated. In this study, using gene knockout mice, we show that Rap1b is the dominant isoform in B cells. Lack of Rap1b significantly reduced the absolute number of B220(+)IgM(-) pro/pre-B cells and B220(+)IgM(+) immature B cells in bone marrow. In vitro culture of bone marrow-derived Rap1b(-/-) pro/pre-B cells with IL-7 showed similar proliferation levels but reduced adhesion to stromal cell line compared with wild type. Rap1b(-/-) mice displayed reduced splenic marginal zone (MZ) B cells, and increased newly forming B cells, whereas the number of follicular B cells was normal. Functionally, Rap1b(-/-) mice showed reduced T-dependent but normal T-independent humoral responses. B cells from Rap1b(-/-) mice showed reduced migration to SDF-1, CXCL13 and in vivo homing to lymph nodes. MZ B cells showed reduced sphingosine-1-phosphate-induced migration and adhesion to ICAM-1. However, absence of Rap1b did not affect splenic B cell proliferation, BCR-mediated activation of Erk1/2, p38 MAPKs, and AKT. Thus, Rap1b is crucial for early B cell development, MZ B cell homeostasis and T-dependent humoral immunity.
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Affiliation(s)
- Haiyan Chu
- Laboratory of Molecular Immunology, Medical College of Wisconsin, Milwaukee, WI 53226, USA
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30
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Stieglitz B, Bee C, Schwarz D, Yildiz O, Moshnikova A, Khokhlatchev A, Herrmann C. Novel type of Ras effector interaction established between tumour suppressor NORE1A and Ras switch II. EMBO J 2008; 27:1995-2005. [PMID: 18596699 DOI: 10.1038/emboj.2008.125] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2008] [Accepted: 06/04/2008] [Indexed: 12/30/2022] Open
Abstract
A class of putative Ras effectors called Ras association domain family (RASSF) represents non-enzymatic adaptors that were shown to be important in tumour suppression. RASSF5, a member of this family, exists in two splice variants known as NORE1A and RAPL. Both of them are involved in distinct cellular pathways triggered by Ras and Rap, respectively. Here we describe the crystal structure of Ras in complex with the Ras binding domain (RBD) of NORE1A/RAPL. All Ras effectors share a common topology in their RBD creating an interface with the switch I region of Ras, whereas NORE1A/RAPL RBD reveals additional structural elements forming a unique Ras switch II binding site. Consequently, the contact area of NORE1A is extended as compared with other Ras effectors. We demonstrate that the enlarged interface provides a rationale for an exceptionally long lifetime of the complex. This is a specific attribute characterizing the effector function of NORE1A/RAPL as adaptors, in contrast to classical enzymatic effectors such as Raf, RalGDS or PI3K, which are known to form highly dynamic short-lived complexes with Ras.
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Affiliation(s)
- Benjamin Stieglitz
- Physikalische Chemie 1, Fakultät für Chemie und Biochemie, Ruhr-Universität Bochum, Bochum, Germany
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31
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Lin KBL, Freeman SA, Zabetian S, Brugger H, Weber M, Lei V, Dang-Lawson M, Tse KWK, Santamaria R, Batista FD, Gold MR. The rap GTPases regulate B cell morphology, immune-synapse formation, and signaling by particulate B cell receptor ligands. Immunity 2008; 28:75-87. [PMID: 18191594 DOI: 10.1016/j.immuni.2007.11.019] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2007] [Revised: 10/19/2007] [Accepted: 11/19/2007] [Indexed: 01/17/2023]
Abstract
B lymphocytes spread and extend membrane processes when searching for antigens and form immune synapses upon contacting cells that display antigens on their surface. Although these dynamic morphological changes facilitate B cell activation, the signaling pathways underlying these processes are not fully understood. We found that activation of the Rap GTPases was essential for these changes in B cell morphology. Rap activation was important for B cell receptor (BCR)- and lymphocyte-function-associated antigen-1 (LFA-1)-induced spreading, for BCR-induced immune-synapse formation, and for particulate BCR ligands to induce localized F-actin assembly and membrane-process extension. Rap activation and F-actin assembly were also required for optimal BCR signaling in response to particulate antigens but not soluble antigens. Thus by controlling B cell morphology and cytoskeletal organization, Rap might play a key role in the activation of B cells by particulate and cell-associated antigens.
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Affiliation(s)
- Kevin B L Lin
- Department of Microbiology and Immunology, I3 and CELL Research Groups, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
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