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Mohr I, Mirzaiebadizi A, Sanyal SK, Chuenban P, Ahmadian MR, Ivanov R, Bauer P. Characterization of the small Arabidopsis thaliana GTPase and ADP-ribosylation factor-like 2 protein TITAN 5. J Cell Sci 2024; 137:jcs262315. [PMID: 39056156 DOI: 10.1242/jcs.262315] [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: 05/31/2024] [Accepted: 06/03/2024] [Indexed: 07/28/2024] Open
Abstract
Small GTPases switch between GDP- and GTP-bound states during cell signaling. The ADP-ribosylation factor (ARF) family of small GTPases is involved in vesicle trafficking. Although evolutionarily well conserved, little is known about ARF and ARF-like GTPases in plants. We characterized biochemical properties and cellular localization of the essential small ARF-like GTPase TITAN 5 (TTN5; also known as HALLIMASCH, ARL2 and ARLC1) from Arabidopsis thaliana, and two TTN5 proteins with point mutants in conserved residues, TTN5T30N and TTN5Q70L, that were expected to be unable to perform nucleotide exchange and GTP hydrolysis, respectively. TTN5 exhibited very rapid intrinsic nucleotide exchange and remarkably low GTP hydrolysis activity, functioning as a non-classical small GTPase being likely present in a GTP-loaded active form. We analyzed signals from YFP-TTN5 and HA3-TTN5 by in situ immunolocalization in Arabidopsis seedlings and through use of a transient expression system. Colocalization with endomembrane markers and pharmacological treatments suggests that TTN5 can be present at the plasma membrane and that it dynamically associates with membranes of vesicles, Golgi stacks and multivesicular bodies. Although TTN5Q70L mirrored wild-type TTN5 behavior, the TTN5T30N mutant differed in some aspects. Hence, the unusual rapid nucleotide exchange activity of TTN5 is linked with its membrane dynamics, and TTN5 likely has a role in vesicle transport within the endomembrane system.
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Affiliation(s)
- Inga Mohr
- Institute of Botany, Heinrich Heine University, 40225 Düsseldorf, Germany
| | - Amin Mirzaiebadizi
- Institute of Biochemistry and Molecular Biology II, Medical Faculty and University Hospital Düsseldorf, Heinrich Heine University, 40225 Düsseldorf, Germany
| | - Sibaji K Sanyal
- Institute of Botany, Heinrich Heine University, 40225 Düsseldorf, Germany
| | - Pichaporn Chuenban
- Institute of Botany, Heinrich Heine University, 40225 Düsseldorf, Germany
- Center for Plant Genome Engineering, Heinrich Heine University, 40225 Düsseldorf, Germany
| | - Mohammad R Ahmadian
- Institute of Biochemistry and Molecular Biology II, Medical Faculty and University Hospital Düsseldorf, Heinrich Heine University, 40225 Düsseldorf, Germany
| | - Rumen Ivanov
- Institute of Botany, Heinrich Heine University, 40225 Düsseldorf, Germany
| | - Petra Bauer
- Institute of Botany, Heinrich Heine University, 40225 Düsseldorf, Germany
- Cluster of Excellence on Plant Sciences, Heinrich Heine University, 40225 Düsseldorf, Germany
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2
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Mohr I, Mirzaiebadizi A, Sanyal SK, Chuenban P, Ahmadian MR, Ivanov R, Bauer P. Characterization of the small Arabidopsis thaliana GTPase and ADP-ribosylation factor-like 2 protein TITAN 5. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.04.27.538563. [PMID: 37162876 PMCID: PMC10168340 DOI: 10.1101/2023.04.27.538563] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Small GTPases function by conformational switching ability between GDP- and GTP-bound states in rapid cell signaling events. The ADP-ribosylation factor (ARF) family is involved in vesicle trafficking. Though evolutionarily well conserved, little is known about ARF and ARF-like GTPases in plants. Here, we characterized biochemical properties and cellular localization of the essential small ARF-like GTPase TITAN 5/HALLIMASCH/ARL2/ARLC1 (hereafter termed TTN5) from Arabidopsis thaliana. Two TTN5 variants were included in the study with point mutations at conserved residues, suspected to be functional for nucleotide exchange and GTP hydrolysis, TTN5T30N and TTN5Q70L. We found that TTN5 had a very rapid intrinsic nucleotide exchange capacity with a conserved nucleotide switching mechanism. TTN5 acted as a non-classical small GTPase with a remarkably low GTP hydrolysis activity, suggesting it is likely present in GTP-loaded active form in the cell. We analyzed signals from yellow fluorescent protein (YFP)-tagged TTN5 and from in situ immunolocalization of hemagglutine-tagged HA3-TTN5 in Arabidopsis seedlings and in a transient expression system. Together with colocalization using endomembrane markers and pharmacological treatments the microscopic analysis suggests that TTN5 can be present at the plasma membrane and dynamically associated with membranes of vesicles, Golgi stacks and multivesicular bodies. While the TTN5Q70L variant showed similar GTPase activities and localization behavior as wild-type TTN5, the TTN5T30N mutant differed in some aspects. Hence, the unusual capacity of rapid nucleotide exchange activity of TTN5 is linked with cell membrane dynamics, likely associated with vesicle transport pathways in the endomembrane system.
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Affiliation(s)
- Inga Mohr
- Institute of Botany, Heinrich Heine University, 40225 Düsseldorf, Germany
| | - Amin Mirzaiebadizi
- Institute of Biochemistry and Molecular Biology II, Medical Faculty and University Hospital Düsseldorf, Heinrich Heine University, Düsseldorf, Germany
| | - Sibaji K Sanyal
- Institute of Botany, Heinrich Heine University, 40225 Düsseldorf, Germany
| | - Pichaporn Chuenban
- Institute of Botany, Heinrich Heine University, 40225 Düsseldorf, Germany
| | - Mohammad R Ahmadian
- Institute of Biochemistry and Molecular Biology II, Medical Faculty and University Hospital Düsseldorf, Heinrich Heine University, Düsseldorf, Germany
| | - Rumen Ivanov
- Institute of Botany, Heinrich Heine University, 40225 Düsseldorf, Germany
| | - Petra Bauer
- Institute of Botany, Heinrich Heine University, 40225 Düsseldorf, Germany
- Cluster of Excellence on Plant Sciences, Heinrich Heine University, 40225 Düsseldorf, Germany
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3
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Rosenberg EM, Jian X, Soubias O, Jackson RA, Gladu E, Andersen E, Esser L, Sodt AJ, Xia D, Byrd RA, Randazzo PA. Point mutations in Arf1 reveal cooperative effects of the N-terminal extension and myristate for GTPase-activating protein catalytic activity. PLoS One 2024; 19:e0295103. [PMID: 38574162 PMCID: PMC10994351 DOI: 10.1371/journal.pone.0295103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2023] [Accepted: 03/05/2024] [Indexed: 04/06/2024] Open
Abstract
The ADP-ribosylation factors (Arfs) constitute a family of small GTPases within the Ras superfamily, with a distinguishing structural feature of a hypervariable N-terminal extension of the G domain modified with myristate. Arf proteins, including Arf1, have roles in membrane trafficking and cytoskeletal dynamics. While screening for Arf1:small molecule co-crystals, we serendipitously solved the crystal structure of the non-myristoylated engineered mutation [L8K]Arf1 in complex with a GDP analogue. Like wild-type (WT) non-myristoylated Arf1•GDP, we observed that [L8K]Arf1 exhibited an N-terminal helix that occludes the hydrophobic cavity that is occupied by the myristoyl group in the GDP-bound state of the native protein. However, the helices were offset from one another due to the L8K mutation, with a significant change in position of the hinge region connecting the N-terminus to the G domain. Hypothesizing that the observed effects on behavior of the N-terminus affects interaction with regulatory proteins, we mutated two hydrophobic residues to examine the role of the N-terminal extension for interaction with guanine nucleotide exchange factors (GEFs) and GTPase Activating Proteins (GAPs. Different than previous studies, all mutations were examined in the context of myristoylated Arf. Mutations had little or no effect on spontaneous or GEF-catalyzed guanine nucleotide exchange but did affect interaction with GAPs. [F13A]myrArf1 was less than 1/2500, 1/1500, and 1/200 efficient as substrate for the GAPs ASAP1, ARAP1 and AGAP1; however, [L8A/F13A]myrArf1 was similar to WT myrArf1. Using molecular dynamics simulations, the effect of the mutations on forming alpha helices adjacent to a membrane surface was examined, yet no differences were detected. The results indicate that lipid modifications of GTPases and consequent anchoring to a membrane influences protein function beyond simple membrane localization. Hypothetical mechanisms are discussed.
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Affiliation(s)
- Eric M. Rosenberg
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, MD, United States of America
| | - Xiaoying Jian
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, MD, United States of America
| | - Olivier Soubias
- Section of Macromolecular NMR, Center for Structural Biology Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD, United States of America
| | - Rebekah A. Jackson
- Section of Macromolecular NMR, Center for Structural Biology Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD, United States of America
| | - Erin Gladu
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, MD, United States of America
| | - Emily Andersen
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, MD, United States of America
| | - Lothar Esser
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, United States of America
| | - Alexander J. Sodt
- Unit of Membrane Chemical Physics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD, United States of America
| | - Di Xia
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, United States of America
| | - R. Andrew Byrd
- Section of Macromolecular NMR, Center for Structural Biology Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD, United States of America
| | - Paul A. Randazzo
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, MD, United States of America
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Lübke S, Braukmann C, Rexer KH, Cigoja L, Rout P, Önel SF. The Abl-interactor Abi suppresses the function of the BRAG2 GEF family member Schizo. Biol Open 2024; 13:bio058666. [PMID: 34897417 PMCID: PMC10810563 DOI: 10.1242/bio.058666] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Accepted: 11/27/2021] [Indexed: 11/20/2022] Open
Abstract
Guanine nucleotide exchange factors (GEF) of the BRAG subfamily activate small Arf GTPases, which are pivotal regulators of intracellular membrane traffic and actin dynamics. Consequently, BRAG proteins have been implicated to regulate the surface levels of adhesive and signaling receptors. However, not much is known about the mechanism leading to the regulation of these surface proteins. In this study, we found that the Drosophila BRAG GEF Schizo interacts physically with the Abl-interactor (Abi). schizo mutants display severe defects in myoblast fusion during syncytial muscle formation and show increased amounts of the cell adhesion protein N-cadherin. We demonstrate that the schizo myoblast fusion phenotype can be rescued by the expression of the Schizo GEF (Sec7) and membrane-binding (pleckstrin homology) domain. Furthermore, the expression of the Sec7-PH domain in a wild-type background decreases the amounts of N-cadherin and impairs myoblast fusion. These findings support the notion that the Sec7-PH domain serves as a constitutive-active form of Schizo. Using a yeast-two hybrid assay, we show that the SH3 domain of Abi interacts with the N-terminal region of Schizo. This region is also able to bind to the cytodomain of the cell adhesion molecule N-cadherin. To shed light on the function of Schizo and Abi in N-cadherin removal, we employed epistasis experiments in different developmental contexts of Drosophila. These studies point towards a new model for the regulation of Schizo. We propose that the binding of Abi to the N-terminal part of Schizo antagonizes Schizo function to inhibit N-cadherin removal.
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Affiliation(s)
- Stefanie Lübke
- Fachbereich Medizin, Department for Molecular Cell Physiology, Institute for Physiology and Pathophysiology, Philipps-Universität Marburg, Emil-Mannkopff-Str. 2, 35037 Marburg, Germany
- Fachbereich Biologie, Department for Developmental Biology, Philipps-Universität Marburg, Karl-von-Frisch-Str. 8, 35043 Marburg, Germany
- DFG Research Training Group, Membrane Plasticity in Tissue Development and Remodeling, GRK 2213, Philipps-Universität Marburg, Marburg, Germany
| | - Carina Braukmann
- Fachbereich Biologie, Department for Developmental Biology, Philipps-Universität Marburg, Karl-von-Frisch-Str. 8, 35043 Marburg, Germany
| | - Karl-Heinz Rexer
- Fachbereich Biologie, Department for Biodiversity of Plants, Philipps-Universität Marburg, Karl-von-Frisch-Str. 8, 35043 Marburg, Germany
| | - Lubjinka Cigoja
- Fachbereich Biologie, Department for Developmental Biology, Philipps-Universität Marburg, Karl-von-Frisch-Str. 8, 35043 Marburg, Germany
| | - Pratiti Rout
- DFG Research Training Group, Membrane Plasticity in Tissue Development and Remodeling, GRK 2213, Philipps-Universität Marburg, Marburg, Germany
- Fachbereich Biologie, Department for Molecular Embryology, Philipps-Universität Marburg, Karl-von-Frisch-Str. 8, 35043 Marburg, Germany
| | - Susanne F. Önel
- Fachbereich Medizin, Department for Molecular Cell Physiology, Institute for Physiology and Pathophysiology, Philipps-Universität Marburg, Emil-Mannkopff-Str. 2, 35037 Marburg, Germany
- Fachbereich Biologie, Department for Developmental Biology, Philipps-Universität Marburg, Karl-von-Frisch-Str. 8, 35043 Marburg, Germany
- DFG Research Training Group, Membrane Plasticity in Tissue Development and Remodeling, GRK 2213, Philipps-Universität Marburg, Marburg, Germany
- Fachbereich Biologie, Department for Molecular Embryology, Philipps-Universität Marburg, Karl-von-Frisch-Str. 8, 35043 Marburg, Germany
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5
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Bai G, Li H, Qin P, Guo Y, Yang W, Lian Y, Ye F, Chen J, Wu M, Huang R, Li J, Lu Y, Zhang M. Ca2+-induced release of IQSEC2/BRAG1 autoinhibition under physiological and pathological conditions. J Cell Biol 2023; 222:e202307117. [PMID: 37787765 PMCID: PMC10548395 DOI: 10.1083/jcb.202307117] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Revised: 08/31/2023] [Accepted: 09/14/2023] [Indexed: 10/04/2023] Open
Abstract
IQSEC2 (aka BRAG1) is a guanine nucleotide exchange factor (GEF) highly enriched in synapses. As a top neurodevelopmental disorder risk gene, numerous mutations are identified in Iqsec2 in patients with intellectual disabilities accompanied by other developmental, neurological, and psychiatric symptoms, though with poorly understood underlying molecular mechanisms. The atomic structures of IQSECs, together with biochemical analysis, presented in this study reveal an autoinhibition and Ca2+-dependent allosteric activation mechanism for all IQSECs and rationalize how each identified Iqsec2 mutation can alter the structure and function of the enzyme. Transgenic mice modeling two pathogenic variants of Iqsec2 (R359C and Q801P), with one activating and the other inhibiting the GEF activity of the enzyme, recapitulate distinct clinical phenotypes in patients. Our study demonstrates that different mutations on one gene such as Iqsec2 can have distinct neurological phenotypes and accordingly will require different therapeutic strategies.
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Affiliation(s)
- Guanhua Bai
- School of Life Sciences, Southern University of Science and Technology, Shenzhen, China
- Division of Life Science, State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Kowloon, China
| | - Hao Li
- Department of Pathophysiology, School of Basic Medicine and Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
- The Institute for Brain Research, Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan, China
| | - Pengwei Qin
- Department of Pathophysiology, School of Basic Medicine and Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
- The Institute for Brain Research, Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan, China
| | - Yiqing Guo
- Department of Pathophysiology, School of Basic Medicine and Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
- The Institute for Brain Research, Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan, China
| | - Wanfa Yang
- Division of Life Science, State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Kowloon, China
| | - Yinmiao Lian
- Department of Pathophysiology, School of Basic Medicine and Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
- The Institute for Brain Research, Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan, China
| | - Fei Ye
- Division of Life Science, State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Kowloon, China
| | - Jianxin Chen
- State Key Laboratory of Cell Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China
- School of Life Science and Technology, Shanghai Tech University, Shanghai, China
| | - Meiling Wu
- School of Life Sciences, Southern University of Science and Technology, Shenzhen, China
| | - Ruifeng Huang
- School of Life Sciences, Southern University of Science and Technology, Shenzhen, China
| | - Jinsong Li
- State Key Laboratory of Cell Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China
- School of Life Science and Technology, Shanghai Tech University, Shanghai, China
| | - Youming Lu
- Department of Pathophysiology, School of Basic Medicine and Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
- The Institute for Brain Research, Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan, China
| | - Mingjie Zhang
- School of Life Sciences, Southern University of Science and Technology, Shenzhen, China
- Division of Life Science, State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Kowloon, China
- Greater Bay Biomedical Innocenter, Shenzhen Bay Laboratory, Shenzhen, China
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Sun D, Guo Y, Tang P, Li H, Chen L. Arf6 as a therapeutic target: Structure, mechanism, and inhibitors. Acta Pharm Sin B 2023; 13:4089-4104. [PMID: 37799386 PMCID: PMC10547916 DOI: 10.1016/j.apsb.2023.06.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Revised: 04/28/2023] [Accepted: 06/02/2023] [Indexed: 10/07/2023] Open
Abstract
ADP-ribosylation factor 6 (Arf6), a small G-protein of the Ras superfamily, plays pivotal roles in multiple cellular events, including exocytosis, endocytosis, actin remodeling, plasma membrane reorganization and vesicular transport. Arf6 regulates the progression of cancer through the activation of cell motility and invasion. Aberrant Arf6 activation is a potential therapeutic target. This review aims to understand the comprehensive function of Arf6 for future cancer therapy. The Arf6 GEFs, protein structure, and roles in cancer have been summarized. Comprehending the mechanism underlying Arf6-mediated cancer cell growth and survival is essential. The structural features of Arf6 and its efforts are discussed and may be contributed to the discovery of future novel protein-protein interaction inhibitors. In addition, Arf6 inhibitors and mechanism of action are listed in the table. This review further emphasizes the crucial roles in drug resistance and attempts to offer an outlook of Arf6 in cancer therapy.
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Affiliation(s)
- Dejuan Sun
- Wuya College of Innovation, Key Laboratory of Structure-Based Drug Design & Discovery, Ministry of Education, Shenyang Pharmaceutical University, Shenyang 110016, China
| | - Yuanyuan Guo
- Wuya College of Innovation, Key Laboratory of Structure-Based Drug Design & Discovery, Ministry of Education, Shenyang Pharmaceutical University, Shenyang 110016, China
| | - Piyu Tang
- Wuya College of Innovation, Key Laboratory of Structure-Based Drug Design & Discovery, Ministry of Education, Shenyang Pharmaceutical University, Shenyang 110016, China
| | - Hua Li
- Wuya College of Innovation, Key Laboratory of Structure-Based Drug Design & Discovery, Ministry of Education, Shenyang Pharmaceutical University, Shenyang 110016, China
- College of Pharmacy, Fujian University of Traditional Chinese Medicine, Fuzhou 350122, China
| | - Lixia Chen
- Wuya College of Innovation, Key Laboratory of Structure-Based Drug Design & Discovery, Ministry of Education, Shenyang Pharmaceutical University, Shenyang 110016, China
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Powis G, Meuillet EJ, Indarte M, Booher G, Kirkpatrick L. Pleckstrin Homology [PH] domain, structure, mechanism, and contribution to human disease. Biomed Pharmacother 2023; 165:115024. [PMID: 37399719 DOI: 10.1016/j.biopha.2023.115024] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Accepted: 06/14/2023] [Indexed: 07/05/2023] Open
Abstract
The pleckstrin homology [PH] domain is a structural fold found in more than 250 proteins making it the 11th most common domain in the human proteome. 25% of family members have more than one PH domain and some PH domains are split by one, or several other, protein domains although still folding to give functioning PH domains. We review mechanisms of PH domain activity, the role PH domain mutation plays in human disease including cancer, hyperproliferation, neurodegeneration, inflammation, and infection, and discuss pharmacotherapeutic approaches to regulate PH domain activity for the treatment of human disease. Almost half PH domain family members bind phosphatidylinositols [PIs] that attach the host protein to cell membranes where they interact with other membrane proteins to give signaling complexes or cytoskeleton scaffold platforms. A PH domain in its native state may fold over other protein domains thereby preventing substrate access to a catalytic site or binding with other proteins. The resulting autoinhibition can be released by PI binding to the PH domain, or by protein phosphorylation thus providing fine tuning of the cellular control of PH domain protein activity. For many years the PH domain was thought to be undruggable until high-resolution structures of human PH domains allowed structure-based design of novel inhibitors that selectively bind the PH domain. Allosteric inhibitors of the Akt1 PH domain have already been tested in cancer patients and for proteus syndrome, with several other PH domain inhibitors in preclinical development for treatment of other human diseases.
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Affiliation(s)
- Garth Powis
- PHusis Therapeutics Inc., 6019 Folsom Drive, La Jolla, CA 92037, USA.
| | | | - Martin Indarte
- PHusis Therapeutics Inc., 6019 Folsom Drive, La Jolla, CA 92037, USA
| | - Garrett Booher
- PHusis Therapeutics Inc., 6019 Folsom Drive, La Jolla, CA 92037, USA
| | - Lynn Kirkpatrick
- PHusis Therapeutics Inc., 6019 Folsom Drive, La Jolla, CA 92037, USA
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8
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Rosenberg EM, Jian X, Soubias O, Yoon HY, Yadav MP, Hammoudeh S, Pallikkuth S, Akpan I, Chen PW, Maity TK, Jenkins LM, Yohe ME, Byrd RA, Randazzo PA. The small molecule inhibitor NAV-2729 has a complex target profile including multiple ADP-ribosylation factor regulatory proteins. J Biol Chem 2023; 299:102992. [PMID: 36758799 PMCID: PMC10023970 DOI: 10.1016/j.jbc.2023.102992] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 01/18/2023] [Accepted: 01/20/2023] [Indexed: 02/11/2023] Open
Abstract
The ADP-ribosylation factor (Arf) GTPases and their regulatory proteins are implicated in cancer progression. NAV-2729 was previously identified as a specific inhibitor of Arf6 that reduced progression of uveal melanoma in an orthotopic xenograft. Here, our goal was to assess the inhibitory effects of NAV-2729 on the proliferation of additional cell types. We found NAV-2729 inhibited proliferation of multiple cell lines, but Arf6 expression did not correlate with NAV-2729 sensitivity, and knockdown of Arf6 affected neither cell viability nor sensitivity to NAV-2729. Furthermore, binding to native Arf6 was not detected; however, we determined that NAV-2729 inhibited both Arf exchange factors and Arf GTPase-activating proteins. ASAP1, a GTPase-activating protein linked to cancer progression, was further investigated. We demonstrated that NAV-2729 bound to the PH domain of ASAP1 and changed ASAP1 cellular distribution. However, ASAP1 knockdown did not fully recapitulate the cytoskeletal effects of NAV-2729 nor affect cell proliferation. Finally, our screens identified 48 other possible targets of NAV-2729. These results illustrate the complexities of defining targets of small molecules and identify NAV-2729 as a model PH domain-binding inhibitor.
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Affiliation(s)
- Eric M Rosenberg
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, USA
| | - Xiaoying Jian
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, USA
| | - Olivier Soubias
- Center for Structural Biology Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, USA
| | - Hye-Young Yoon
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, USA
| | - Mukesh P Yadav
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, USA
| | - Sarah Hammoudeh
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, USA
| | - Sandeep Pallikkuth
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, USA
| | - Itoro Akpan
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, USA
| | - Pei-Wen Chen
- Department of Biology, Williams College, Williamstown, Massachusetts, USA
| | - Tapan K Maity
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, USA
| | - Lisa M Jenkins
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, USA
| | - Marielle E Yohe
- Pediatric Oncology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, USA; Laboratory of Cell and Developmental Signaling, Center for Cancer Research, Frederick, Maryland, USA
| | - R Andrew Byrd
- Center for Structural Biology Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, USA
| | - Paul A Randazzo
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, USA.
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9
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Nawrotek A, Dubois P, Zeghouf M, Cherfils J. Molecular principles of bidirectional signalling between membranes and small GTPases. FEBS Lett 2023; 597:778-793. [PMID: 36700390 DOI: 10.1002/1873-3468.14585] [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: 10/29/2022] [Revised: 12/23/2022] [Accepted: 12/30/2022] [Indexed: 01/27/2023]
Abstract
Most small GTPases actuate their functions on subcellular membranes, which are increasingly seen as integral components of small GTPase signalling. In this review, we used the highly studied regulation of Arf GTPases by their GEFs to categorize the molecular principles of membrane contributions to small GTPase signalling, which have been highlighted by integrated structural biology combining in vitro reconstitutions in artificial membranes and high-resolution structures. As an illustration of how this framework can be harnessed to better understand the cooperation between small GTPases, their regulators and membranes, we applied it to the activation of the small GTPase Rac1 by DOCK-ELMO, identifying novel contributions of membranes to Rac1 activation. We propose that these structure-based principles should be considered when interrogating the mechanisms whereby small GTPase systems ensure spatial and temporal control of cellular signalling on membranes.
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Affiliation(s)
- Agata Nawrotek
- CNRS, Ecole Normale Supérieure Paris-Saclay and Université Paris-Saclay, Gif-sur-Yvette, France
| | - Pavlina Dubois
- CNRS, Ecole Normale Supérieure Paris-Saclay and Université Paris-Saclay, Gif-sur-Yvette, France
| | - Mahel Zeghouf
- CNRS, Ecole Normale Supérieure Paris-Saclay and Université Paris-Saclay, Gif-sur-Yvette, France
| | - Jacqueline Cherfils
- CNRS, Ecole Normale Supérieure Paris-Saclay and Université Paris-Saclay, Gif-sur-Yvette, France
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10
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Boyd RJ, Olson TL, Zook JD, Stein D, Aceves M, Lin WH, Craciunescu FM, Hansen DT, Anastasiadis PZ, Singharoy A, Fromme P. Characterization and computational simulation of human Syx, a RhoGEF implicated in glioblastoma. FASEB J 2022; 36:e22378. [PMID: 35639414 PMCID: PMC9262375 DOI: 10.1096/fj.202101808rr] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2021] [Revised: 05/10/2022] [Accepted: 05/13/2022] [Indexed: 12/04/2022]
Abstract
Structural discovery of guanine nucleotide exchange factor (GEF) protein complexes is likely to become increasingly relevant with the development of new therapeutics targeting small GTPases and development of new classes of small molecules that inhibit protein‐protein interactions. Syx (also known as PLEKHG5 in humans) is a RhoA GEF implicated in the pathology of glioblastoma (GBM). Here we investigated protein expression and purification of ten different human Syx constructs and performed biophysical characterizations and computational studies that provide insights into why expression of this protein was previously intractable. We show that human Syx can be expressed and isolated and Syx is folded as observed by circular dichroism (CD) spectroscopy and actively binds to RhoA as determined by co‐elution during size exclusion chromatography (SEC). This characterization may provide critical insights into the expression and purification of other recalcitrant members of the large class of oncogenic—Diffuse B‐cell lymphoma (Dbl) homology GEF proteins. In addition, we performed detailed homology modeling and molecular dynamics simulations on the surface of a physiologically realistic membrane. These simulations reveal novel insights into GEF activity and allosteric modulation by the plekstrin homology (PH) domain. These newly revealed interactions between the GEF PH domain and the membrane embedded region of RhoA support previously unexplained experimental findings regarding the allosteric effects of the PH domain from numerous activity studies of Dbl homology GEF proteins. This work establishes new hypotheses for structural interactivity and allosteric signal modulation in Dbl homology RhoGEFs.
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Affiliation(s)
- Ryan J Boyd
- Biodesign Center for Applied Structural Discovery, Arizona State University, Tempe, Arizona, USA
| | - Tien L Olson
- Biodesign Center for Applied Structural Discovery, Arizona State University, Tempe, Arizona, USA
| | - James D Zook
- Biodesign Center for Applied Structural Discovery, Arizona State University, Tempe, Arizona, USA
| | - Derek Stein
- Biodesign Center for Applied Structural Discovery, Arizona State University, Tempe, Arizona, USA
| | - Manuel Aceves
- Biodesign Center for Applied Structural Discovery, Arizona State University, Tempe, Arizona, USA
| | - Wan-Hsin Lin
- Department of Cancer Biology, Mayo Clinic, Jacksonville, Florida, USA
| | - Felicia M Craciunescu
- Biodesign Center for Applied Structural Discovery, Arizona State University, Tempe, Arizona, USA
| | - Debra T Hansen
- Biodesign Center for Applied Structural Discovery, Arizona State University, Tempe, Arizona, USA.,Center for Innovations in Medicine, Arizona State University, Tempe, Arizona, USA
| | | | - Abhishek Singharoy
- Biodesign Center for Applied Structural Discovery, Arizona State University, Tempe, Arizona, USA
| | - Petra Fromme
- Biodesign Center for Applied Structural Discovery, Arizona State University, Tempe, Arizona, USA
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11
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Blaise AM, Corcoran EE, Wattenberg ES, Zhang YL, Cottrell JR, Koleske AJ. In vitro fluorescence assay to measure GDP/GTP exchange of guanine nucleotide exchange factors of Rho family GTPases. Biol Methods Protoc 2021; 7:bpab024. [PMID: 35087952 PMCID: PMC8789339 DOI: 10.1093/biomethods/bpab024] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Revised: 12/14/2021] [Indexed: 11/14/2022] Open
Abstract
Guanine nucleotide exchange factors (GEFs) are enzymes that promote the activation of GTPases through GTP loading. Whole exome sequencing has identified rare variants in GEFs that are associated with disease, demonstrating that GEFs play critical roles in human development. However, the consequences of these rare variants can only be understood through measuring their effects on cellular activity. Here, we provide a detailed, user-friendly protocol for purification and fluorescence-based analysis of the two GEF domains within the protein, Trio. This analysis offers a straight-forward, quantitative tool to test the activity of GEF domains on their respective GTPases, as well as utilize high-throughput screening to identify regulators and inhibitors. This protocol can be adapted for characterization of other Rho family GEFs. Such analyses are crucial for the complete understanding of the roles of GEF genetic variants in human development and disease.
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Affiliation(s)
- Alyssa M Blaise
- Departments of Molecular Biophysics and Biochemistry, Yale School of Medicine, Yale University, New Haven, CT 06520-8024, USA
- Neuroscience, Yale School of Medicine, Yale University, New Haven, CT 06520-8024, USA
| | - Ellen E Corcoran
- Departments of Molecular Biophysics and Biochemistry, Yale School of Medicine, Yale University, New Haven, CT 06520-8024, USA
- Neuroscience, Yale School of Medicine, Yale University, New Haven, CT 06520-8024, USA
| | - Eve S Wattenberg
- Departments of Molecular Biophysics and Biochemistry, Yale School of Medicine, Yale University, New Haven, CT 06520-8024, USA
- Neuroscience, Yale School of Medicine, Yale University, New Haven, CT 06520-8024, USA
| | - Yan-Ling Zhang
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Jeffrey R Cottrell
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Anthony J Koleske
- Departments of Molecular Biophysics and Biochemistry, Yale School of Medicine, Yale University, New Haven, CT 06520-8024, USA
- Neuroscience, Yale School of Medicine, Yale University, New Haven, CT 06520-8024, USA
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12
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Chen PW, Gasilina A, Yadav MP, Randazzo PA. Control of cell signaling by Arf GTPases and their regulators: Focus on links to cancer and other GTPase families. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2021; 1869:119171. [PMID: 34774605 DOI: 10.1016/j.bbamcr.2021.119171] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Revised: 10/23/2021] [Accepted: 11/04/2021] [Indexed: 12/31/2022]
Abstract
The ADP-ribosylation factors (Arfs) comprise a family of regulatory GTP binding proteins. The Arfs regulate membrane trafficking and cytoskeleton remodeling, processes critical for eukaryotes and which have been the focus of most studies on Arfs. A more limited literature describes a role in signaling and in integrating several signaling pathways to bring about specific cell behaviors. Here, we will highlight work describing function of Arf1, Arf6 and several effectors and regulators of Arfs in signaling.
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Affiliation(s)
- Pei-Wen Chen
- Department of Biology, Williams College, Williamstown, MA, United States of America
| | - Anjelika Gasilina
- National Heart, Lung and Blood Institute, NIH, Bethesda, MD, United States of America(1); Laboratory of Cellular and Molecular Biology, National Cancer Institute, NIH, Bethesda, MD, United States of America
| | - Mukesh P Yadav
- Laboratory of Cellular and Molecular Biology, National Cancer Institute, NIH, Bethesda, MD, United States of America
| | - Paul A Randazzo
- Laboratory of Cellular and Molecular Biology, National Cancer Institute, NIH, Bethesda, MD, United States of America.
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13
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Protein-membrane interactions in small GTPase signalling and pharmacology: perspectives from Arf GTPases studies. Biochem Soc Trans 2020; 48:2721-2728. [PMID: 33336699 DOI: 10.1042/bst20200482] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Revised: 11/12/2020] [Accepted: 11/13/2020] [Indexed: 11/17/2022]
Abstract
Small GTPases, in association with their GEFs, GAPs and effectors, control major intracellular processes such as signal transduction, cytoskeletal dynamics and membrane trafficking. Accordingly, dysfunctions in their biochemical properties are associated with many diseases, including cancers, diabetes, infections, mental disorders and cardiac diseases, which makes them attractive targets for therapies. However, small GTPases signalling modules are not well-suited for classical inhibition strategies due to their mode of action that combines protein-protein and protein-membrane interactions. As a consequence, there is still no validated drug available on the market that target small GTPases, whether directly or through their regulators. Alternative inhibitory strategies are thus highly needed. Here we review recent studies that highlight the unique modalities of the interaction of small GTPases and their GEFs at the periphery of membranes, and discuss how they can be harnessed in drug discovery.
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14
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Petersen A, Brown JC, Gerges NZ. BRAG1/IQSEC2 as a regulator of small GTPase-dependent trafficking. Small GTPases 2020; 11:1-7. [PMID: 29363391 PMCID: PMC6959296 DOI: 10.1080/21541248.2017.1361898] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2017] [Revised: 07/25/2017] [Accepted: 07/27/2017] [Indexed: 10/18/2022] Open
Abstract
Precise trafficking events, such as those that underlie synaptic transmission and plasticity, require complex regulation. G-protein signaling plays an essential role in the regulation of membrane and protein trafficking. However, it is not well understood how small GTPases and their regulatory proteins coordinate such specific events. Our recent publication focused on a highly abundant synaptic GEF, BRAG1, whose physiologic relevance was unknown. We find that BRAG1s GEF activity is required for activity-dependent trafficking of AMPARs. Moreover, BRAG1 bidirectionally regulates synaptic transmission in a manner independent of this activity. In addition to the GEF domain, BRAG1 contains several functional domains whose roles are not yet understood but may mediate protein-protein interactions and regulatory effects necessary for its role in regulation of AMPAR trafficking. In this commentary, we explore the potential for BRAG1 to provide specificity of small GTPase signaling, coordinating activity-dependent activation of small GTPase activity with signaling and scaffolding molecules involved in trafficking through its GEF activity and other functional domains.
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Affiliation(s)
- Amber Petersen
- Department of Cell Biology, Neurobiology and Anatomy, The Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - Joshua C. Brown
- Department of Psychiatry and Behavioral Science, Medical University of South Carolina, Charleston, SC, USA
| | - Nashaat Z. Gerges
- Department of Cell Biology, Neurobiology and Anatomy, The Medical College of Wisconsin, Milwaukee, Wisconsin, USA
- Department of Biopharmaceutical Sciences, School of Pharmacy, The Medical College of Wisconsin, Milwaukee, Wisconsin, USA
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15
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Roy NS, Jian X, Soubias O, Zhai P, Hall JR, Dagher JN, Coussens NP, Jenkins LM, Luo R, Akpan IO, Hall MD, Byrd RA, Yohe ME, Randazzo PA. Interaction of the N terminus of ADP-ribosylation factor with the PH domain of the GTPase-activating protein ASAP1 requires phosphatidylinositol 4,5-bisphosphate. J Biol Chem 2019; 294:17354-17370. [PMID: 31591270 DOI: 10.1074/jbc.ra119.009269] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2019] [Revised: 10/02/2019] [Indexed: 12/15/2022] Open
Abstract
Arf GAP with Src homology 3 domain, ankyrin repeat, and pleckstrin homology (PH) domain 1 (ASAP1) is a multidomain GTPase-activating protein (GAP) for ADP-ribosylation factor (ARF)-type GTPases. ASAP1 affects integrin adhesions, the actin cytoskeleton, and invasion and metastasis of cancer cells. ASAP1's cellular function depends on its highly-regulated and robust ARF GAP activity, requiring both the PH and the ARF GAP domains of ASAP1, and is modulated by phosphatidylinositol 4,5-bisphosphate (PIP2). The mechanistic basis of PIP2-stimulated GAP activity is incompletely understood. Here, we investigated whether PIP2 controls binding of the N-terminal extension of ARF1 to ASAP1's PH domain and thereby regulates its GAP activity. Using [Δ17]ARF1, lacking the N terminus, we found that PIP2 has little effect on ASAP1's activity. A soluble PIP2 analog, dioctanoyl-PIP2 (diC8PIP2), stimulated GAP activity on an N terminus-containing variant, [L8K]ARF1, but only marginally affected activity on [Δ17]ARF1. A peptide comprising residues 2-17 of ARF1 ([2-17]ARF1) inhibited GAP activity, and PIP2-dependently bound to a protein containing the PH domain and a 17-amino acid-long interdomain linker immediately N-terminal to the first β-strand of the PH domain. Point mutations in either the linker or the C-terminal α-helix of the PH domain decreased [2-17]ARF1 binding and GAP activity. Mutations that reduced ARF1 N-terminal binding to the PH domain also reduced the effect of ASAP1 on cellular actin remodeling. Mutations in the ARF N terminus that reduced binding also reduced GAP activity. We conclude that PIP2 regulates binding of ASAP1's PH domain to the ARF1 N terminus, which may partially regulate GAP activity.
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Affiliation(s)
- Neeladri Sekhar Roy
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892
| | - Xiaoying Jian
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892
| | - Olivier Soubias
- Structural Biophysics Laboratory, Center for Cancer Research, NCI, National Institutes of Health, Frederick, Maryland 21702
| | - Peng Zhai
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892
| | - Jessica R Hall
- Chemical Genomics Center, National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland 20892
| | - Jessica N Dagher
- Chemical Genomics Center, National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland 20892
| | - Nathan P Coussens
- Chemical Genomics Center, National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland 20892
| | - Lisa M Jenkins
- Laboratory of Cell Biology, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892
| | - Ruibai Luo
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892
| | - Itoro O Akpan
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892
| | - Matthew D Hall
- Chemical Genomics Center, National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland 20892
| | - R Andrew Byrd
- Structural Biophysics Laboratory, Center for Cancer Research, NCI, National Institutes of Health, Frederick, Maryland 21702
| | - Marielle E Yohe
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892 .,Pediatric Oncology Branch, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892
| | - Paul A Randazzo
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892
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16
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Sztul E, Chen PW, Casanova JE, Cherfils J, Dacks JB, Lambright DG, Lee FJS, Randazzo PA, Santy LC, Schürmann A, Wilhelmi I, Yohe ME, Kahn RA. ARF GTPases and their GEFs and GAPs: concepts and challenges. Mol Biol Cell 2019; 30:1249-1271. [PMID: 31084567 PMCID: PMC6724607 DOI: 10.1091/mbc.e18-12-0820] [Citation(s) in RCA: 156] [Impact Index Per Article: 31.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2019] [Revised: 02/26/2019] [Accepted: 03/11/2019] [Indexed: 12/12/2022] Open
Abstract
Detailed structural, biochemical, cell biological, and genetic studies of any gene/protein are required to develop models of its actions in cells. Studying a protein family in the aggregate yields additional information, as one can include analyses of their coevolution, acquisition or loss of functionalities, structural pliability, and the emergence of shared or variations in molecular mechanisms. An even richer understanding of cell biology can be achieved through evaluating functionally linked protein families. In this review, we summarize current knowledge of three protein families: the ARF GTPases, the guanine nucleotide exchange factors (ARF GEFs) that activate them, and the GTPase-activating proteins (ARF GAPs) that have the ability to both propagate and terminate signaling. However, despite decades of scrutiny, our understanding of how these essential proteins function in cells remains fragmentary. We believe that the inherent complexity of ARF signaling and its regulation by GEFs and GAPs will require the concerted effort of many laboratories working together, ideally within a consortium to optimally pool information and resources. The collaborative study of these three functionally connected families (≥70 mammalian genes) will yield transformative insights into regulation of cell signaling.
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Affiliation(s)
- Elizabeth Sztul
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL 35294
| | - Pei-Wen Chen
- Department of Biology, Williams College, Williamstown, MA 01267
| | - James E. Casanova
- Department of Cell Biology, University of Virginia, Charlottesville, VA 22908
| | - Jacqueline Cherfils
- Laboratoire de Biologie et Pharmacologie Appliquée, CNRS and Ecole Normale Supérieure Paris-Saclay, 94235 Cachan, France
| | - Joel B. Dacks
- Division of Infectious Disease, Department of Medicine, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | - David G. Lambright
- Program in Molecular Medicine and Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Amherst, MA 01605
| | - Fang-Jen S. Lee
- Institute of Molecular Medicine, College of Medicine, National Taiwan University, Taipei 10002, Taiwan
| | | | - Lorraine C. Santy
- Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA 16802
| | - Annette Schürmann
- German Institute of Human Nutrition, 85764 Potsdam-Rehbrücke, Germany
| | - Ilka Wilhelmi
- German Institute of Human Nutrition, 85764 Potsdam-Rehbrücke, Germany
| | - Marielle E. Yohe
- Pediatric Oncology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892
| | - Richard A. Kahn
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA 30322-3050
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17
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Nawrotek A, Benabdi S, Niyomchon S, Kryszke MH, Ginestier C, Cañeque T, Tepshi L, Mariani A, St Onge RP, Giaever G, Nislow C, Charafe-Jauffret E, Rodriguez R, Zeghouf M, Cherfils J. PH-domain-binding inhibitors of nucleotide exchange factor BRAG2 disrupt Arf GTPase signaling. Nat Chem Biol 2019; 15:358-366. [PMID: 30742123 DOI: 10.1038/s41589-019-0228-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2018] [Accepted: 11/29/2018] [Indexed: 12/30/2022]
Abstract
Peripheral membrane proteins orchestrate many physiological and pathological processes, making regulation of their activities by small molecules highly desirable. However, they are often refractory to classical competitive inhibition. Here, we demonstrate that potent and selective inhibition of peripheral membrane proteins can be achieved by small molecules that target protein-membrane interactions by a noncompetitive mechanism. We show that the small molecule Bragsin inhibits BRAG2-mediated Arf GTPase activation in vitro in a manner that requires a membrane. In cells, Bragsin affects the trans-Golgi network in a BRAG2- and Arf-dependent manner. The crystal structure of the BRAG2-Bragsin complex and structure-activity relationship analysis reveal that Bragsin binds at the interface between the PH domain of BRAG2 and the lipid bilayer to render BRAG2 unable to activate lipidated Arf. Finally, Bragsin affects tumorsphere formation in breast cancer cell lines. Bragsin thus pioneers a novel class of drugs that function by altering protein-membrane interactions without disruption.
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Affiliation(s)
- Agata Nawrotek
- Laboratoire de Biologie et Pharmacologie Appliquée, Ecole normale supérieure Paris-Saclay, Cachan, France.,CNRS, Cachan, France
| | - Sarah Benabdi
- Laboratoire de Biologie et Pharmacologie Appliquée, Ecole normale supérieure Paris-Saclay, Cachan, France.,CNRS, Cachan, France
| | - Supaporn Niyomchon
- Institut Curie, PSL Research University, Chemical Cell Biology Group, Paris, France.,CNRS, Paris, France.,INSERM, Paris, France
| | - Marie-Hélène Kryszke
- Laboratoire de Biologie et Pharmacologie Appliquée, Ecole normale supérieure Paris-Saclay, Cachan, France.,CNRS, Cachan, France
| | - Christophe Ginestier
- Université Aix-Marseille, CNRS, INSERM, Institut Paoli-Calmettes, CRCM, Epithelial Stem Cells and Cancer Team, Marseille, France
| | - Tatiana Cañeque
- Institut Curie, PSL Research University, Chemical Cell Biology Group, Paris, France.,CNRS, Paris, France.,INSERM, Paris, France
| | - Livia Tepshi
- Laboratoire de Biologie et Pharmacologie Appliquée, Ecole normale supérieure Paris-Saclay, Cachan, France.,CNRS, Cachan, France
| | - Angelica Mariani
- Institut Curie, PSL Research University, Chemical Cell Biology Group, Paris, France.,CNRS, Paris, France.,INSERM, Paris, France
| | - Robert P St Onge
- Genome Technology Center, Stanford School of Medicine, Stanford, CA, USA
| | - Guri Giaever
- Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, Canada
| | - Corey Nislow
- Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, Canada
| | - Emmanuelle Charafe-Jauffret
- Université Aix-Marseille, CNRS, INSERM, Institut Paoli-Calmettes, CRCM, Epithelial Stem Cells and Cancer Team, Marseille, France
| | - Raphaël Rodriguez
- Institut Curie, PSL Research University, Chemical Cell Biology Group, Paris, France.,CNRS, Paris, France.,INSERM, Paris, France
| | - Mahel Zeghouf
- Laboratoire de Biologie et Pharmacologie Appliquée, Ecole normale supérieure Paris-Saclay, Cachan, France. .,CNRS, Cachan, France.
| | - Jacqueline Cherfils
- Laboratoire de Biologie et Pharmacologie Appliquée, Ecole normale supérieure Paris-Saclay, Cachan, France. .,CNRS, Cachan, France.
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18
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Multiple interactions between an Arf/GEF complex and charged lipids determine activation kinetics on the membrane. Proc Natl Acad Sci U S A 2017; 114:11416-11421. [PMID: 28923919 DOI: 10.1073/pnas.1707970114] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Lipidated small GTPases and their regulators need to bind to membranes to propagate actions in the cell, but an integrated understanding of how the lipid bilayer exerts its effect has remained elusive. Here we focused on ADP ribosylation factor (Arf) GTPases, which orchestrate a variety of regulatory functions in lipid and membrane trafficking, and their activation by the guanine-nucleotide exchange factor (GEF) Brag2, which controls integrin endocytosis and cell adhesion and is impaired in cancer and developmental diseases. Biochemical and structural data are available that showed the exceptional efficiency of Arf activation by Brag2 on membranes. We determined the high-resolution crystal structure of unbound Brag2 containing the GEF (Sec7) and membrane-binding (pleckstrin homology) domains, revealing that it has a constitutively active conformation. We used this structure to analyze the interaction of uncomplexed Brag2 and of the myristoylated Arf1/Brag2 complex with a phosphatidylinositol bisphosphate (PIP2) -containing lipid bilayer, using coarse-grained molecular dynamics. These simulations revealed that the system forms a close-packed, oriented interaction with the membrane, in which multiple PIP2 lipids bind the canonical lipid-binding site and unique peripheral sites of the PH domain, the Arf GTPase and, unexpectedly, the Sec7 domain. We cross-validated these predictions by reconstituting the binding and kinetics of Arf and Brag2 in artificial membranes. Our coarse-grained structural model thus suggests that the high efficiency of Brag2 requires interaction with multiple lipids and a well-defined orientation on the membrane, resulting in a local PIP2 enrichment, which has the potential to signal toward the Arf pathway.
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19
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Benabdi S, Peurois F, Nawrotek A, Chikireddy J, Cañeque T, Yamori T, Shiina I, Ohashi Y, Dan S, Rodriguez R, Cherfils J, Zeghouf M. Family-wide Analysis of the Inhibition of Arf Guanine Nucleotide Exchange Factors with Small Molecules: Evidence of Unique Inhibitory Profiles. Biochemistry 2017; 56:5125-5133. [PMID: 28858527 DOI: 10.1021/acs.biochem.7b00706] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Arf GTPases and their guanine nucleotide exchange factors (ArfGEFs) are major regulators of membrane traffic and organelle structure in cells. They are associated with a variety of diseases and are thus attractive therapeutic targets for inhibition by small molecules. Several inhibitors of unrelated chemical structures have been discovered, which have shown their potential in dissecting molecular pathways and blocking disease-related functions. However, their specificity across the ArfGEF family has remained elusive. Importantly, inhibitory responses in the context of membranes, which are critical determinants of Arf and ArfGEF cellular functions, have not been investigated. Here, we compare the efficiency and specificity of four structurally distinct ArfGEF inhibitors, Brefeldin A, SecinH3, M-COPA, and NAV-2729, toward six ArfGEFs (human ARNO, EFA6, BIG1, and BRAG2 and Legionella and Rickettsia RalF). Inhibition was assessed by fluorescence kinetics using pure proteins, and its modulation by membranes was determined with lipidated GTPases in the presence of liposomes. Our analysis shows that despite the intra-ArfGEF family resemblance, each inhibitor has a specific inhibitory profile. Notably, M-COPA is a potent pan-ArfGEF inhibitor, and NAV-2729 inhibits all GEFs, the strongest effects being against BRAG2 and Arf1. Furthermore, the presence of the membrane-binding domain in Legionella RalF reveals a strong inhibitory effect of BFA that is not measured on its GEF domain alone. This study demonstrates the value of family-wide assays with incorporation of membranes, and it should enable accurate dissection of Arf pathways by these inhibitors to best guide their use and development as therapeutic agents.
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Affiliation(s)
- Sarah Benabdi
- Laboratoire de Biologie et Pharmacologie Appliquée CNRS, Ecole Normale Supérieure Paris-Saclay , 61 avenue du président Wilson, 94235 Cachan, France
| | - François Peurois
- Laboratoire de Biologie et Pharmacologie Appliquée CNRS, Ecole Normale Supérieure Paris-Saclay , 61 avenue du président Wilson, 94235 Cachan, France
| | - Agata Nawrotek
- Laboratoire de Biologie et Pharmacologie Appliquée CNRS, Ecole Normale Supérieure Paris-Saclay , 61 avenue du président Wilson, 94235 Cachan, France
| | - Jahnavi Chikireddy
- Laboratoire de Biologie et Pharmacologie Appliquée CNRS, Ecole Normale Supérieure Paris-Saclay , 61 avenue du président Wilson, 94235 Cachan, France
| | - Tatiana Cañeque
- Institut Curie, PSL Research University , Chemical Cell Biology group, 26 rue d'Ulm, 75248 Paris Cedex 05, France.,CNRS UMR3666 , 75005 Paris, France.,INSERM U1143 , 75005 Paris, France
| | - Takao Yamori
- Division of Molecular Pharmacology, Cancer Chemotherapy Center, Japanese Foundation for Cancer Research , Tokyo 135-8550, Japan
| | - Isamu Shiina
- Department of Applied Chemistry, Faculty of Science, Tokyo University of Science , Tokyo 162-8601, Japan
| | - Yoshimi Ohashi
- Division of Molecular Pharmacology, Cancer Chemotherapy Center, Japanese Foundation for Cancer Research , Tokyo 135-8550, Japan
| | - Shingo Dan
- Division of Molecular Pharmacology, Cancer Chemotherapy Center, Japanese Foundation for Cancer Research , Tokyo 135-8550, Japan
| | - Raphaël Rodriguez
- Institut Curie, PSL Research University , Chemical Cell Biology group, 26 rue d'Ulm, 75248 Paris Cedex 05, France.,CNRS UMR3666 , 75005 Paris, France.,INSERM U1143 , 75005 Paris, France
| | - Jacqueline Cherfils
- Laboratoire de Biologie et Pharmacologie Appliquée CNRS, Ecole Normale Supérieure Paris-Saclay , 61 avenue du président Wilson, 94235 Cachan, France
| | - Mahel Zeghouf
- Laboratoire de Biologie et Pharmacologie Appliquée CNRS, Ecole Normale Supérieure Paris-Saclay , 61 avenue du président Wilson, 94235 Cachan, France
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20
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Characterization of the activation of small GTPases by their GEFs on membranes using artificial membrane tethering. Biochem J 2017; 474:1259-1272. [PMID: 28196833 DOI: 10.1042/bcj20170015] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Revised: 02/03/2017] [Accepted: 02/13/2017] [Indexed: 12/20/2022]
Abstract
Active, GTP-bound small GTPases need to be attached to membranes by post-translational lipid modifications in order to process and propagate information in cells. However, generating and manipulating lipidated GTPases has remained difficult, which has limited our quantitative understanding of their activation by guanine nucleotide exchange factors (GEFs) and their termination by GTPase-activating proteins. Here, we replaced the lipid modification by a histidine tag in 11 full-length, human small GTPases belonging to the Arf, Rho and Rab families, which allowed to tether them to nickel-lipid-containing membranes and characterize the kinetics of their activation by GEFs. Remarkably, this strategy uncovered large effects of membranes on the efficiency and/or specificity in all systems studied. Notably, it recapitulated the release of autoinhibition of Arf1, Arf3, Arf4, Arf5 and Arf6 GTPases by membranes and revealed that all isoforms are efficiently activated by two GEFs with different regulatory regimes, ARNO and Brag2. It demonstrated that membranes stimulate the GEF activity of Trio toward RhoG by ∼30 fold and Rac1 by ∼10 fold, and uncovered a previously unknown broader specificity toward RhoA and Cdc42 that was undetectable in solution. Finally, it demonstrated that the exceptional affinity of the bacterial RabGEF DrrA for the phosphoinositide PI(4)P delimits the activation of Rab1 to the immediate vicinity of the membrane-bound GEF. Our study thus validates the histidine-tag strategy as a potent and simple means to mimic small GTPase lipidation, which opens a variety of applications to uncover regulations brought about by membranes.
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21
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Várnai P, Gulyás G, Tóth DJ, Sohn M, Sengupta N, Balla T. Quantifying lipid changes in various membrane compartments using lipid binding protein domains. Cell Calcium 2016; 64:72-82. [PMID: 28088320 DOI: 10.1016/j.ceca.2016.12.008] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Revised: 12/28/2016] [Accepted: 12/29/2016] [Indexed: 11/30/2022]
Abstract
One of the largest challenges in cell biology is to map the lipid composition of the membranes of various organelles and define the exact location of processes that control the synthesis and distribution of lipids between cellular compartments. The critical role of phosphoinositides, low-abundant lipids with rapid metabolism and exceptional regulatory importance in the control of almost all aspects of cellular functions created the need for tools to visualize their localizations and dynamics at the single cell level. However, there is also an increasing need for methods to determine the cellular distribution of other lipids regulatory or structural, such as diacylglycerol, phosphatidic acid, or other phospholipids and cholesterol. This review will summarize recent advances in this research field focusing on the means by which changes can be described in more quantitative terms.
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Affiliation(s)
- Péter Várnai
- Department of Physiology, Faculty of Medicine, Semmelweis University, Budapest, Hungary
| | - Gergő Gulyás
- Department of Physiology, Faculty of Medicine, Semmelweis University, Budapest, Hungary
| | - Dániel J Tóth
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, United States; Department of Physiology, Faculty of Medicine, Semmelweis University, Budapest, Hungary
| | - Mira Sohn
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, United States
| | - Nivedita Sengupta
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, United States
| | - Tamas Balla
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, United States.
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22
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Abstract
The IQSec/BRAG proteins are a subfamily of Arf-nucleotide exchange factors. Since their discovery almost 15 y ago, the BRAGs have been reported to be involved in diverse physiological processes from myoblast fusion, neuronal pathfinding and angiogenesis, to pathophysiological processes including X-linked intellectual disability and tumor metastasis. In this review we will address how, in each of these situations, the BRAGs are thought to regulate the surface levels of adhesive and signaling receptors. While in most cases BRAGs are thought to enhance the endocytosis of these receptors, how they achieve this remains unclear. Similarly, while all 3 BRAG proteins contain calmodulin-binding IQ motifs, little is known about how their activities might be regulated by calcium. These are some of the questions that are likely to form the basis of future research.
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Affiliation(s)
- Ryan S D'Souza
- a Department of Cell Biology , University of Virginia Health System , Charlottesville , VA , USA
| | - James E Casanova
- a Department of Cell Biology , University of Virginia Health System , Charlottesville , VA , USA
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23
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Fidler DR, Murphy SE, Courtis K, Antonoudiou P, El-Tohamy R, Ient J, Levine TP. Using HHsearch to tackle proteins of unknown function: A pilot study with PH domains. Traffic 2016; 17:1214-1226. [PMID: 27601190 PMCID: PMC5091641 DOI: 10.1111/tra.12432] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Revised: 08/30/2016] [Accepted: 08/30/2016] [Indexed: 01/08/2023]
Abstract
Advances in membrane cell biology are hampered by the relatively high proportion of proteins with no known function. Such proteins are largely or entirely devoid of structurally significant domain annotations. Structural bioinformaticians have developed profile‐profile tools such as HHsearch (online version called HHpred), which can detect remote homologies that are missed by tools used to annotate databases. Here we have applied HHsearch to study a single structural fold in a single model organism as proof of principle. In the entire clan of protein domains sharing the pleckstrin homology domain fold in yeast, systematic application of HHsearch accurately identified known PH‐like domains. It also predicted 16 new domains in 13 yeast proteins many of which are implicated in intracellular traffic. One of these was Vps13p, where we confirmed the functional importance of the predicted PH‐like domain. Even though such predictions require considerable work to be corroborated, they are useful first steps. HHsearch should be applied more widely, particularly across entire proteomes of model organisms, to significantly improve database annotations.
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Affiliation(s)
- David R Fidler
- Department of Cell Biology, UCL Institute of Ophthalmology, London, UK
| | - Sarah E Murphy
- Department of Cell Biology, UCL Institute of Ophthalmology, London, UK
| | - Katherine Courtis
- Department of Cell Biology, UCL Institute of Ophthalmology, London, UK
| | | | - Rana El-Tohamy
- Department of Cell Biology, UCL Institute of Ophthalmology, London, UK
| | - Jonathan Ient
- Department of Cell Biology, UCL Institute of Ophthalmology, London, UK
| | - Timothy P Levine
- Department of Cell Biology, UCL Institute of Ophthalmology, London, UK.
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24
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Nawrotek A, Zeghouf M, Cherfils J. Allosteric regulation of Arf GTPases and their GEFs at the membrane interface. Small GTPases 2016; 7:283-296. [PMID: 27449855 DOI: 10.1080/21541248.2016.1215778] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Arf GTPases assemble protein complexes on membranes to carry out major functions in cellular traffic. An essential step is their activation by guanine nucleotide exchange factors (GEFs), whose Sec7 domain stimulates GDP/GTP exchange. ArfGEFs form 2 major families: ArfGEFs with DCB, HUS and HDS domains (GBF1 and BIG1/BIG2 in humans), which act at the Golgi; and ArfGEFs with a C-terminal PH domain (cytohesin, EFA6 and BRAG), which function at the plasma membrane and endosomes. In addition, pathogenic bacteria encode an ArfGEF with a unique membrane-binding domain. Here we review the allosteric regulation of Arf GTPases and their GEFs at the membrane interface. Membranes contribute several regulatory layers: at the GTPase level, where activation by GTP is coupled to membrane recruitment by a built-in structural device; at the Sec7 domain, which manipulates this device to ensure that Arf-GTP is attached to membranes; and at the level of non-catalytic ArfGEF domains, which form direct or GTPase-mediated interactions with membranes that enable a spectacular diversity of regulatory regimes. Notably, we show here that membranes increase the efficiency of a large ArfGEF (human BIG1) by 32-fold by interacting directly with its N-terminal DCB and HUS domains. The diversity of allosteric regulatory regimes suggests that ArfGEFs can function in cascades and circuits to modulate the shape, amplitude and duration of Arf signals in cells. Because Arf-like GTPases feature autoinhibitory elements similar to those of Arf GTPases, we propose that their activation also requires allosteric interactions of these elements with membranes or other proteins.
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Affiliation(s)
- Agata Nawrotek
- a Laboratoire de Biologie et Pharmacologie Appliquée, CNRS, Ecole Normale Supérieure de Cachan and Université Paris-Saclay , Cachan , France
| | - Mahel Zeghouf
- a Laboratoire de Biologie et Pharmacologie Appliquée, CNRS, Ecole Normale Supérieure de Cachan and Université Paris-Saclay , Cachan , France
| | - Jacqueline Cherfils
- a Laboratoire de Biologie et Pharmacologie Appliquée, CNRS, Ecole Normale Supérieure de Cachan and Université Paris-Saclay , Cachan , France
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25
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Roy NS, Yohe ME, Randazzo PA, Gruschus JM. Allosteric properties of PH domains in Arf regulatory proteins. CELLULAR LOGISTICS 2016; 6:e1181700. [PMID: 27294009 DOI: 10.1080/21592799.2016.1181700] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Revised: 04/13/2016] [Accepted: 04/14/2016] [Indexed: 10/21/2022]
Abstract
Pleckstrin Homology (PH) domains bind phospholipids and proteins. They are critical regulatory elements of a number enzymes including guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs) for Ras-superfamily guanine nucleotide binding proteins such as ADP-ribosylation factors (Arfs). Recent studies have indicated that many PH domains may bind more than one ligand cooperatively. Here we discuss the molecular basis of PH domain-dependent allosteric behavior of 2 ADP-ribosylation factor exchange factors, Grp1 and Brag2, cooperative binding of ligands to the PH domains of Grp1 and the Arf GTPase-activating protein, ASAP1, and the consequences for activity of the associated catalytic domains.
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Affiliation(s)
- Neeladri Sekhar Roy
- Laboratory of Cellular and Molecular Biology, National Cancer Institute, National Institutes of Health , Bethesda, MD, USA
| | - Marielle E Yohe
- Genetics Branch, National Cancer Institute, National Institutes of Health , Bethesda, MD, USA
| | - Paul A Randazzo
- Laboratory of Cellular and Molecular Biology, National Cancer Institute, National Institutes of Health , Bethesda, MD, USA
| | - James M Gruschus
- Laboratory of Structural Biophysics, National Heart, Lung and Blood Institute, National Institutes of Health , Bethesda, MD, USA
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26
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Abstract
Mutant genes that underlie Mendelian forms of amyotrophic lateral sclerosis (ALS) and biochemical investigations of genetic disease models point to potential driver pathophysiological events involving endoplasmic reticulum (ER) stress and autophagy. Several steps in these cell biological processes are known to be controlled physiologically by small ADP-ribosylation factor (ARF) signaling. Here, we investigated the role of ARF guanine nucleotide exchange factors (GEFs), cytohesins, in models of ALS. Genetic or pharmacological inhibition of cytohesins protects motor neurons in vitro from proteotoxic insults and rescues locomotor defects in a Caenorhabditis elegans model of disease. Cytohesins form a complex with mutant superoxide dismutase 1 (SOD1), a known cause of familial ALS, but this is not associated with a change in GEF activity or ARF activation. ER stress evoked by mutant SOD1 expression is alleviated by antagonism of cytohesin activity. In the setting of mutant SOD1 toxicity, inhibition of cytohesin activity enhances autophagic flux and reduces the burden of misfolded SOD1. These observations suggest that targeting cytohesins may have potential benefits for the treatment of ALS.
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27
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Chen PW, Jian X, Luo R, Randazzo PA. Simple in vitro assay of Arf GAPs and preparation of Arf proteins as substrates. Methods Cell Biol 2015; 130:69-80. [PMID: 26360029 DOI: 10.1016/bs.mcb.2015.03.021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Defining the interaction of Arf GAPs with specific Arfs is important for understanding their functions in the endocytic system. Cell-based approaches have been valuable for identifying Arfs and Arf GAPs active in the endocytic compartment; however, the cell-based assays have some limitations in establishing relationships among the Arfs and ArfGAPs. Here we describe a simple in vitro assay that will provide a means for comparing Arfs as substrates and serve to complement cell-based studies.
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Affiliation(s)
- Pei-Wen Chen
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, MD, USA
| | - Xiaoying Jian
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, MD, USA
| | - Ruibai Luo
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, MD, USA
| | - Paul A Randazzo
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, MD, USA
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28
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Hammond GRV, Balla T. Polyphosphoinositide binding domains: Key to inositol lipid biology. Biochim Biophys Acta Mol Cell Biol Lipids 2015; 1851:746-58. [PMID: 25732852 DOI: 10.1016/j.bbalip.2015.02.013] [Citation(s) in RCA: 168] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Revised: 01/29/2015] [Accepted: 02/17/2015] [Indexed: 01/01/2023]
Abstract
Polyphosphoinositides (PPIn) are an important family of phospholipids located on the cytoplasmic leaflet of eukaryotic cell membranes. Collectively, they are critical for the regulation of many aspects of membrane homeostasis and signaling, with notable relevance to human physiology and disease. This regulation is achieved through the selective interaction of these lipids with hundreds of cellular proteins, and thus the capability to study these localized interactions is crucial to understanding their functions. In this review, we discuss current knowledge of the principle types of PPIn-protein interactions, focusing on specific lipid-binding domains. We then discuss how these domains have been re-tasked by biologists as molecular probes for these lipids in living cells. Finally, we describe how the knowledge gained with these probes, when combined with other techniques, has led to the current view of the lipids' localization and function in eukaryotes, focusing mainly on animal cells. This article is part of a Special Issue entitled Phosphoinositides.
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Affiliation(s)
- Gerald R V Hammond
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
| | - Tamas Balla
- Section on Molecular Signal Transduction, Eunice Shriver Kennedy National Institute for Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA.
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29
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EFA6 controls Arf1 and Arf6 activation through a negative feedback loop. Proc Natl Acad Sci U S A 2014; 111:12378-83. [PMID: 25114232 DOI: 10.1073/pnas.1409832111] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Guanine nucleotide exchange factors (GEFs) of the exchange factor for Arf6 (EFA6), brefeldin A-resistant Arf guanine nucleotide exchange factor (BRAG), and cytohesin subfamilies activate small GTPases of the Arf family in endocytic events. These ArfGEFs carry a pleckstrin homology (PH) domain in tandem with their catalytic Sec7 domain, which is autoinhibitory and supports a positive feedback loop in cytohesins but not in BRAGs, and has an as-yet unknown role in EFA6 regulation. In this study, we analyzed how EFA6A is regulated by its PH and C terminus (Ct) domains by reconstituting its GDP/GTP exchange activity on membranes. We found that EFA6 has a previously unappreciated high efficiency toward Arf1 on membranes and that, similar to BRAGs, its PH domain is not autoinhibitory and strongly potentiates nucleotide exchange on anionic liposomes. However, in striking contrast to both cytohesins and BRAGs, EFA6 is regulated by a negative feedback loop, which is mediated by an allosteric interaction of Arf6-GTP with the PH-Ct domain of EFA6 and monitors the activation of Arf1 and Arf6 differentially. These observations reveal that EFA6, BRAG, and cytohesins have unanticipated commonalities associated with divergent regulatory regimes. An important implication is that EFA6 and cytohesins may combine in a mixed negative-positive feedback loop. By allowing EFA6 to sustain a pool of dormant Arf6-GTP, such a circuit would fulfill the absolute requirement of cytohesins for activation by Arf-GTP before amplification of their GEF activity by their positive feedback loop.
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30
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Manavski Y, Carmona G, Bennewitz K, Tang Z, Zhang F, Sakurai A, Zeiher AM, Gutkind JS, Li X, Kroll J, Dimmeler S, Chavakis E. Brag2 differentially regulates β1- and β3-integrin-dependent adhesion in endothelial cells and is involved in developmental and pathological angiogenesis. Basic Res Cardiol 2014; 109:404. [DOI: 10.1007/s00395-014-0404-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/22/2013] [Revised: 01/19/2014] [Accepted: 01/28/2014] [Indexed: 11/29/2022]
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31
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Randazzo PA, Jian X, Chen PW, Zhai P, Soubias O, Northup JK. Quantitative Analysis of Guanine Nucleotide Exchange Factors (GEFs) as Enzymes. CELLULAR LOGISTICS 2014; 3:e27609. [PMID: 25332840 PMCID: PMC4187004 DOI: 10.4161/cl.27609] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/17/2013] [Revised: 12/19/2013] [Accepted: 12/20/2013] [Indexed: 11/19/2022]
Abstract
The proteins that possess guanine nucleotide exchange factor (GEF) activity, which include about ~800 G protein coupled receptors (GPCRs),1 15 Arf GEFs,2 81 Rho GEFs,3 8 Ras GEFs,4 and others for other families of GTPases,5 catalyze the exchange of GTP for GDP on all regulatory guanine nucleotide binding proteins. Despite their importance as catalysts, relatively few exchange factors (we are aware of only eight for ras superfamily members) have been rigorously characterized kinetically.5-13 In some cases, kinetic analysis has been simplistic leading to erroneous conclusions about mechanism (as discussed in a recent review14). In this paper, we compare two approaches for determining the kinetic properties of exchange factors: (i) examining individual equilibria, and; (ii) analyzing the exchange factors as enzymes. Each approach, when thoughtfully used,14,15 provides important mechanistic information about the exchange factors. The analysis as enzymes is described in further detail. With the focus on the production of the biologically relevant guanine nucleotide binding protein complexed with GTP (G•GTP), we believe it is conceptually simpler to connect the kinetic properties to cellular effects. Further, the experiments are often more tractable than those used to analyze the equilibrium system and, therefore, more widely accessible to scientists interested in the function of exchange factors.
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Affiliation(s)
- Paul A Randazzo
- Laboratory of Cellular and Molecular Biology; National Cancer Institute; Bethesda, MD USA
| | - Xiaoying Jian
- Laboratory of Cellular and Molecular Biology; National Cancer Institute; Bethesda, MD USA
| | - Pei-Wen Chen
- Laboratory of Cellular and Molecular Biology; National Cancer Institute; Bethesda, MD USA
| | - Peng Zhai
- Laboratory of Cellular and Molecular Biology; National Cancer Institute; Bethesda, MD USA
| | - Olivier Soubias
- Laboratory of Membrane Biochemistry and Biophysics; National Institute on Alcohol Abuse and Alcoholism; Rockville, MD USA
| | - John K Northup
- Laboratory of Membrane Biochemistry and Biophysics; National Institute on Alcohol Abuse and Alcoholism; Rockville, MD USA
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32
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Aizel K, Biou V, Navaza J, Duarte LV, Campanacci V, Cherfils J, Zeghouf M. Integrated conformational and lipid-sensing regulation of endosomal ArfGEF BRAG2. PLoS Biol 2013; 11:e1001652. [PMID: 24058294 PMCID: PMC3769224 DOI: 10.1371/journal.pbio.1001652] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2013] [Accepted: 07/31/2013] [Indexed: 11/24/2022] Open
Abstract
The structure of endosomal ArfGEF BRAG2 in complex with Arf1, combined with an analysis of this GEF's efficiency on membranes, reveals a regulatory mechanism that simultaneously optimizes membrane recruitment and nucleotide exchange. The mechanisms whereby guanine nucleotide exchange factors (GEFs) coordinate their subcellular targeting to their activation of small GTPases remain poorly understood. Here we analyzed how membranes control the efficiency of human BRAG2, an ArfGEF involved in receptor endocytosis, Wnt signaling, and tumor invasion. The crystal structure of an Arf1–BRAG2 complex that mimics a membrane-bound intermediate revealed an atypical PH domain that is constitutively anchored to the catalytic Sec7 domain and interacts with Arf. Combined with the quantitative analysis of BRAG2 exchange activity reconstituted on membranes, we find that this PH domain potentiates nucleotide exchange by about 2,000-fold by cumulative conformational and membrane-targeting contributions. Furthermore, it restricts BRAG2 activity to negatively charged membranes without phosphoinositide specificity, using a positively charged surface peripheral to but excluding the canonical lipid-binding pocket. This suggests a model of BRAG2 regulation along the early endosomal pathway that expands the repertoire of GEF regulatory mechanisms. Notably, it departs from the auto-inhibitory and feedback loop paradigm emerging from studies of SOS and cytohesins. It also uncovers a novel mechanism of unspecific lipid-sensing by PH domains that may allow sustained binding to maturating membranes. Understanding the molecular mechanisms that allow guanine exchange factor proteins (GEFs) to coordinate their GDP/GTP exchange activity with their being targeted to specific intracellular membranes is an important issue. In this study, we solved the crystal structure of the ArfGEF BRAG2, an endosomal protein that is involved in invasive phenotypes in various tumors, in a complex with the small GTPase Arf1. We show that the pleckstrin homology (PH) domain of BRAG2 atypically does not auto-inhibit its Sec7 domain (as has been seen in ArfGEFs belonging to the cytohesin family), but instead potentiates nucleotide exchange 10-fold in solution and up to 2,000-fold in the presence of liposomes. This stimulatory effect requires negatively charged membranes, and does not involve a preference of the PH domain for specific phosphoinositides or the use of its canonical lipid-binding pocket. This uncovers a regulatory mechanism in which the PH domain controls GEF efficiency by concurrently optimizing membrane recruitment and nucleotide exchange.
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Affiliation(s)
- Kaheina Aizel
- Laboratoire d'Enzymologie et Biochimie Structurales, CNRS, Gif-sur-Yvette, France
| | - Valérie Biou
- Laboratoire d'Enzymologie et Biochimie Structurales, CNRS, Gif-sur-Yvette, France
| | - Jorge Navaza
- Institut de Biologie Structurale, CNRS/CEA/Université Joseph Fourier, Grenoble, France
- Unidad de Biofísica CSIC-UPV/EHU, Leioa, Bizkaia, Spain
| | - Lionel V. Duarte
- Laboratoire d'Enzymologie et Biochimie Structurales, CNRS, Gif-sur-Yvette, France
| | - Valérie Campanacci
- Laboratoire d'Enzymologie et Biochimie Structurales, CNRS, Gif-sur-Yvette, France
| | - Jacqueline Cherfils
- Laboratoire d'Enzymologie et Biochimie Structurales, CNRS, Gif-sur-Yvette, France
- * E-mail: (JC); (MZ)
| | - Mahel Zeghouf
- Laboratoire d'Enzymologie et Biochimie Structurales, CNRS, Gif-sur-Yvette, France
- * E-mail: (JC); (MZ)
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33
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Rouhana J, Padilla A, Estaran S, Bakari S, Delbecq S, Boublik Y, Chopineau J, Pugnière M, Chavanieu A. Kinetics of interaction between ADP-ribosylation factor-1 (Arf1) and the Sec7 domain of Arno guanine nucleotide exchange factor, modulation by allosteric factors, and the uncompetitive inhibitor brefeldin A. J Biol Chem 2012; 288:4659-72. [PMID: 23255605 DOI: 10.1074/jbc.m112.391748] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The GDP/GTP nucleotide exchange of Arf1 is catalyzed by nucleotide exchange factors (GEF), such as Arno, which act through their catalytic Sec7 domain. This exchange is a complex mechanism that undergoes conformational changes and intermediate complex species involving several allosteric partners such as nucleotides, Mg(2+), and Sec7 domains. Using a surface plasmon resonance approach, we characterized the kinetic binding parameters for various intermediate complexes. We first confirmed that both GDP and GTP counteract equivalently to the free-nucleotide binary Arf1-Arno complex stability and revealed that Mg(2+) potentiates by a factor of 2 the allosteric effect of GDP. Then we explored the uncompetitive inhibitory mechanism of brefeldin A (BFA) that conducts to an abortive pentameric Arf1-Mg(2+)-GDP-BFA-Sec7 complex. With BFA, the association rate of the abortive complex is drastically reduced by a factor of 42, and by contrast, the 15-fold decrease of the dissociation rate concurs to stabilize the pentameric complex. These specific kinetic signatures have allowed distinguishing the level and nature as well as the fate in real time of formed complexes according to experimental conditions. Thus, we showed that in the presence of GDP, the BFA-resistant Sec7 domain of Arno can also associate to form a pentameric complex, which suggests that the uncompetitive inhibition by BFA and the nucleotide allosteric effect combine to stabilize such abortive complex.
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Affiliation(s)
- Jad Rouhana
- Institut des Biomolécules Max Mousseron, IBMM, UMR 5247 CNRS-Universités Montpellier 1 et 2 Faculté de Pharmacie, 15 avenue Charles Flahault BP14491, 34093 Montpellier cedex 5, France
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34
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Northup JK, Jian X, Randazzo PA. Nucleotide exchange factors: Kinetic analyses and the rationale for studying kinetics of GEFs. CELLULAR LOGISTICS 2012. [PMID: 23181196 PMCID: PMC3498072 DOI: 10.4161/cl.21627] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Exchange factors are enzymes that catalyze the exchange of GTP for GDP on guanine nucleotide binding proteins. Progress in understanding the molecular basis of action and the cellular functions of these enzymes has largely come from structural determinations (e.g., crystal structures) and studying effects on cells when expression levels of the exchange factors are perturbed or mutated exchange factors are expressed. Proportionally little effort has been expended on studying the kinetics of exchange; however, reaction rates are central to understanding enzymes. Here, we discuss the importance of kinetic analysis of exchange factors for guanine nucleotide binding proteins, with a focus on ADP-ribosylation factor (Arf) and heterotrimeric G proteins, for providing unique insights into molecular mechanisms and regulation as well as how kinetic analyses are used to complement other approaches.
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Affiliation(s)
- John K Northup
- Laboratory of Cellular Biology; National Institute of Deafness and Other Communication Disorders; Rockville, MD USA
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