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Wan N, Hong Z, Parson MAH, Korfhage JL, Burke JE, Melia TJ, Reinisch KM. Spartin-mediated lipid transfer facilitates lipid droplet turnover. Proc Natl Acad Sci U S A 2024; 121:e2314093121. [PMID: 38190532 PMCID: PMC10801920 DOI: 10.1073/pnas.2314093121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2023] [Accepted: 12/01/2023] [Indexed: 01/10/2024] Open
Abstract
Lipid droplets (LDs) are organelles critical for energy storage and membrane lipid homeostasis, whose number and size are carefully regulated in response to cellular conditions. The molecular mechanisms underlying lipid droplet biogenesis and degradation, however, are not well understood. The Troyer syndrome protein spartin (SPG20) supports LD delivery to autophagosomes for turnover via lipophagy. Here, we characterize spartin as a lipid transfer protein whose transfer ability is required for LD degradation. Spartin copurifies with phospholipids and neutral lipids from cells and transfers phospholipids in vitro via its senescence domain. A senescence domain truncation that impairs lipid transfer in vitro also impairs LD turnover in cells while not affecting spartin association with either LDs or autophagosomes, supporting that spartin's lipid transfer ability is physiologically relevant. Our data indicate a role for spartin-mediated lipid transfer in LD turnover.
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Affiliation(s)
- Neng Wan
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT06520
| | - Zhouping Hong
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT06520
| | - Matthew A. H. Parson
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BCV8W2Y2, Canada
| | - Justin L. Korfhage
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT06520
| | - John E. Burke
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BCV8W2Y2, Canada
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BCV6T 1Z3, Canada
| | - Thomas J. Melia
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT06520
| | - Karin M. Reinisch
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT06520
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Wan N, Hong Z, Parson MAH, Korfhage J, Burke JE, Melia TJ, Reinisch KM. Spartin-mediated lipid transfer facilitates lipid droplet turnover. bioRxiv 2023:2023.11.29.569220. [PMID: 38076959 PMCID: PMC10705495 DOI: 10.1101/2023.11.29.569220] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/22/2023]
Abstract
Lipid droplets (LDs) are organelles critical for energy storage and membrane lipid homeostasis, whose number and size are carefully regulated in response to cellular conditions. The molecular mechanisms underlying lipid droplet biogenesis and degradation, however, are not well understood. The Troyer syndrome protein spartin (SPG20) supports LD delivery to autophagosomes for turnover via lipophagy. Here, we characterize spartin as a lipid transfer protein whose transfer ability is required for LD degradation. Spartin co-purifies with phospholipids and neutral lipids from cells and transfers phospholipids in vitro via its senescence domain. A senescence domain truncation that impairs lipid transfer in vitro also impairs LD turnover in cells while not affecting spartin association with either LDs or autophagosomes, supporting that spartin's lipid transfer ability is physiologically relevant. Our data indicate a role for spartin-mediated lipid transfer in LD turnover.
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Affiliation(s)
- Neng Wan
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Zhouping Hong
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Matthew A. H. Parson
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC, Canada V8W2Y2
| | - Justin Korfhage
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520, USA
| | - John E. Burke
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC, Canada V8W2Y2
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada V6T 1Z3
| | - Thomas J. Melia
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Karin M. Reinisch
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520, USA
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Harris NJ, Jenkins ML, Nam SE, Rathinaswamy MK, Parson MAH, Ranga-Prasad H, Dalwadi U, Moeller BE, Sheeky E, Hansen SD, Yip CK, Burke JE. Allosteric activation or inhibition of PI3Kγ mediated through conformational changes in the p110γ helical domain. eLife 2023; 12:RP88058. [PMID: 37417733 PMCID: PMC10392983 DOI: 10.7554/elife.88058] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/08/2023] Open
Abstract
PI3Kγ is a critical immune signaling enzyme activated downstream of diverse cell surface molecules, including Ras, PKCβ activated by the IgE receptor, and Gβγ subunits released from activated GPCRs. PI3Kγ can form two distinct complexes, with the p110γ catalytic subunit binding to either a p101 or p84 regulatory subunit, with these complexes being differentially activated by upstream stimuli. Here, using a combination of cryo electron microscopy, HDX-MS, and biochemical assays, we have identified novel roles of the helical domain of p110γ in regulating lipid kinase activity of distinct PI3Kγ complexes. We defined the molecular basis for how an allosteric inhibitory nanobody potently inhibits kinase activity through rigidifying the helical domain and regulatory motif of the kinase domain. The nanobody did not block either p110γ membrane recruitment or Ras/Gβγ binding, but instead decreased ATP turnover. We also identified that p110γ can be activated by dual PKCβ helical domain phosphorylation leading to partial unfolding of an N-terminal region of the helical domain. PKCβ phosphorylation is selective for p110γ-p84 compared to p110γ-p101, driven by differential dynamics of the helical domain of these different complexes. Nanobody binding prevented PKCβ-mediated phosphorylation. Overall, this work shows an unexpected allosteric regulatory role of the helical domain of p110γ that is distinct between p110γ-p84 and p110γ-p101 and reveals how this can be modulated by either phosphorylation or allosteric inhibitory binding partners. This opens possibilities of future allosteric inhibitor development for therapeutic intervention.
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Affiliation(s)
- Noah J Harris
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, Canada
| | - Meredith L Jenkins
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, Canada
| | - Sung-Eun Nam
- Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, Canada
| | - Manoj K Rathinaswamy
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, Canada
| | - Matthew A H Parson
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, Canada
| | - Harish Ranga-Prasad
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, Canada
| | - Udit Dalwadi
- Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, Canada
| | - Brandon E Moeller
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, Canada
| | - Eleanor Sheeky
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, Canada
| | - Scott D Hansen
- Department of Chemistry and Biochemistry, Institute of Molecular Biology, University of Oregon, Eugene, United States
| | - Calvin K Yip
- Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, Canada
| | - John E Burke
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, Canada
- Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, Canada
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Shaw AL, Parson MAH, Truebestein L, Jenkins ML, Leonard TA, Burke JE. ATP-competitive and allosteric inhibitors induce differential conformational changes at the autoinhibitory interface of Akt1. Structure 2023; 31:343-354.e3. [PMID: 36758543 DOI: 10.1016/j.str.2023.01.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Revised: 12/21/2022] [Accepted: 01/13/2023] [Indexed: 02/11/2023]
Abstract
Akt is a master regulator of pro-growth signaling in the cell. Akt is activated by phosphoinositides that disrupt the autoinhibitory interface between the kinase and pleckstrin homology (PH) domains and then is phosphorylated at T308 and S473. Akt hyperactivation is oncogenic, which has spurred development of potent and selective inhibitors as therapeutics. Using hydrogen deuterium exchange mass spectrometry (HDX-MS), we interrogated the conformational changes upon binding Akt ATP-competitive and allosteric inhibitors. We compared inhibitors against three different states of Akt1. The allosteric inhibitor caused substantive conformational changes and restricts membrane binding. ATP-competitive inhibitors caused extensive allosteric conformational changes, altering the autoinhibitory interface and leading to increased membrane binding, suggesting that the PH domain is more accessible for membrane binding. This work provides unique insight into the autoinhibitory conformation of the PH and kinase domain and conformational changes induced by Akt inhibitors and has important implications for the design of Akt targeted therapeutics.
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Affiliation(s)
- Alexandria L Shaw
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC V8W 2Y2, Canada; Department of Biochemistry and Molecular Biology, the University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Matthew A H Parson
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC V8W 2Y2, Canada
| | - Linda Truebestein
- Department of Structural and Computational Biology, Max Perutz Labs, Campus Vienna Biocenter 5, 1030 Vienna, Austria; Department of Medical Biochemistry, Medical University of Vienna, 1090 Vienna, Austria
| | - Meredith L Jenkins
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC V8W 2Y2, Canada
| | - Thomas A Leonard
- Department of Structural and Computational Biology, Max Perutz Labs, Campus Vienna Biocenter 5, 1030 Vienna, Austria; Department of Medical Biochemistry, Medical University of Vienna, 1090 Vienna, Austria
| | - John E Burke
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC V8W 2Y2, Canada; Department of Biochemistry and Molecular Biology, the University of British Columbia, Vancouver, BC V6T 1Z3, Canada.
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Thibodeau MC, Harris NJ, Jenkins ML, Parson MAH, Evans JT, Scott MK, Shaw AL, Pokorný D, Leonard TA, Burke JE. Molecular basis for the recruitment of the Rab effector protein WDR44 by the GTPase Rab11. J Biol Chem 2022; 299:102764. [PMID: 36463963 PMCID: PMC9808001 DOI: 10.1016/j.jbc.2022.102764] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Revised: 11/22/2022] [Accepted: 11/28/2022] [Indexed: 12/03/2022] Open
Abstract
The formation of complexes between Rab11 and its effectors regulates multiple aspects of membrane trafficking, including recycling and ciliogenesis. WD repeat-containing protein 44 (WDR44) is a structurally uncharacterized Rab11 effector that regulates ciliogenesis by competing with prociliogenesis factors for Rab11 binding. Here, we present a detailed biochemical and biophysical characterization of the WDR44-Rab11 complex and define specific residues mediating binding. Using AlphaFold2 modeling and hydrogen/deuterium exchange mass spectrometry, we generated a molecular model of the Rab11-WDR44 complex. The Rab11-binding domain of WDR44 interacts with switch I, switch II, and the interswitch region of Rab11. Extensive mutagenesis of evolutionarily conserved residues in WDR44 at the interface identified numerous complex-disrupting mutations. Using hydrogen/deuterium exchange mass spectrometry, we found that the dynamics of the WDR44-Rab11 interface are distinct from the Rab11 effector FIP3, with WDR44 forming a more extensive interface with the switch II helix of Rab11 compared with FIP3. The WDR44 interaction was specific to Rab11 over evolutionarily similar Rabs, with mutations defining the molecular basis of Rab11 specificity. Finally, WDR44 can be phosphorylated by Sgk3, with this leading to reorganization of the Rab11-binding surface on WDR44. Overall, our results provide molecular detail on how WDR44 interacts with Rab11 and how Rab11 can form distinct effector complexes that regulate membrane trafficking events.
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Affiliation(s)
- Matthew C Thibodeau
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia, Canada
| | - Noah J Harris
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia, Canada
| | - Meredith L Jenkins
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia, Canada
| | - Matthew A H Parson
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia, Canada
| | - John T Evans
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia, Canada
| | - Mackenzie K Scott
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia, Canada
| | - Alexandria L Shaw
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia, Canada; Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, British Columbia, Canada
| | - Daniel Pokorný
- Max Perutz Labs, Department of Structural and Computational Biology, Vienna, Austria; Department of Medical Biochemistry, Medical University of Vienna, Vienna, Austria
| | - Thomas A Leonard
- Max Perutz Labs, Department of Structural and Computational Biology, Vienna, Austria; Department of Medical Biochemistry, Medical University of Vienna, Vienna, Austria
| | - John E Burke
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia, Canada; Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, British Columbia, Canada.
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Medley BJ, Leclaire L, Thompson N, Mahoney KE, Pluvinage B, Parson MAH, Burke JE, Malaker S, Wakarchuk W, Boraston AB. A previously uncharacterized O-glycopeptidase from Akkermansia muciniphila requires the Tn-antigen for cleavage of the peptide bond. J Biol Chem 2022; 298:102439. [PMID: 36049519 PMCID: PMC9513282 DOI: 10.1016/j.jbc.2022.102439] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Revised: 08/25/2022] [Accepted: 08/26/2022] [Indexed: 10/27/2022] Open
Abstract
Akkermansia muciniphila is key member of the human gut microbiota, impacting many features of host health. A major characteristic of this bacterium is its interaction with host mucin, which is abundant in the gut environment, and its ability to metabolize mucin as a nutrient source. The machinery deployed by A. muciniphila to enable this interaction appears to be extensive and sophisticated, yet it is incompletely defined. The uncharacterized protein AMUC_1438 is encoded by a gene that was previously shown to be upregulated when the bacterium is grown on mucin. This uncharacterized protein has features suggestive of carbohydrate-recognition and peptidase activity, which led us to hypothesize that it has a role in mucin depolymerization. Here we provide structural and functional support for the assignment of AMUC_1438 as a unique O-glycopeptidase with mucin degrading capacity. O-glycopeptidase enzymes recognize glycans but hydrolyze the peptide backbone and are common in host-adapted microbes that colonize or invade mucus layers. Structural, kinetic, and mutagenic analyses point to a metzincin metalloprotease catalytic motif but specific recognition of a GalNAc residue α-linked to serine or threonine (i.e. the Tn-antigen) within the AMUC_1438 active site. The enzyme catalyzes hydrolysis of the bond immediately N-terminal to the glycosylated residue. Additional modelling analyses suggest the presence of a carbohydrate-binding module that may assist in substrate recognition. We anticipate that these results will be fundamental to a wider understanding of the O-glycopeptidase class of enzymes and how they may contribute to host-adaptation.
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Affiliation(s)
- Brendon J Medley
- Department of Biochemistry and Microbiology, University of Victoria, PO Box 1700 STN CSC, Victoria, British Columbia, V8W 2Y2, Canada
| | - Leif Leclaire
- Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9, Canada
| | - Nicole Thompson
- Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9, Canada
| | - Keira E Mahoney
- Department of Chemistry, Yale University, 350 Edward St., New Haven CT, 06511
| | - Benjamin Pluvinage
- Department of Biochemistry and Microbiology, University of Victoria, PO Box 1700 STN CSC, Victoria, British Columbia, V8W 2Y2, Canada
| | - Matthew A H Parson
- Department of Biochemistry and Microbiology, University of Victoria, PO Box 1700 STN CSC, Victoria, British Columbia, V8W 2Y2, Canada
| | - John E Burke
- Department of Biochemistry and Microbiology, University of Victoria, PO Box 1700 STN CSC, Victoria, British Columbia, V8W 2Y2, Canada; Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada
| | - Stacy Malaker
- Department of Chemistry, Yale University, 350 Edward St., New Haven CT, 06511
| | - Warren Wakarchuk
- Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9, Canada
| | - Alisdair B Boraston
- Department of Biochemistry and Microbiology, University of Victoria, PO Box 1700 STN CSC, Victoria, British Columbia, V8W 2Y2, Canada.
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Ulengin-Talkish I, Parson MAH, Jenkins ML, Roy J, Shih AZL, St-Denis N, Gulyas G, Balla T, Gingras AC, Várnai P, Conibear E, Burke JE, Cyert MS. Palmitoylation targets the calcineurin phosphatase to the phosphatidylinositol 4-kinase complex at the plasma membrane. Nat Commun 2021; 12:6064. [PMID: 34663815 PMCID: PMC8523714 DOI: 10.1038/s41467-021-26326-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Accepted: 09/29/2021] [Indexed: 11/25/2022] Open
Abstract
Calcineurin, the conserved protein phosphatase and target of immunosuppressants, is a critical mediator of Ca2+ signaling. Here, to discover calcineurin-regulated processes we examined an understudied isoform, CNAβ1. We show that unlike canonical cytosolic calcineurin, CNAβ1 localizes to the plasma membrane and Golgi due to palmitoylation of its divergent C-terminal tail, which is reversed by the ABHD17A depalmitoylase. Palmitoylation targets CNAβ1 to a distinct set of membrane-associated interactors including the phosphatidylinositol 4-kinase (PI4KA) complex containing EFR3B, PI4KA, TTC7B and FAM126A. Hydrogen-deuterium exchange reveals multiple calcineurin-PI4KA complex contacts, including a calcineurin-binding peptide motif in the disordered tail of FAM126A, which we establish as a calcineurin substrate. Calcineurin inhibitors decrease PI4P production during Gq-coupled GPCR signaling, suggesting that calcineurin dephosphorylates and promotes PI4KA complex activity. In sum, this work discovers a calcineurin-regulated signaling pathway which highlights the PI4KA complex as a regulatory target and reveals that dynamic palmitoylation confers unique localization, substrate specificity and regulation to CNAβ1.
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Affiliation(s)
| | - Matthew A H Parson
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC, Canada
| | - Meredith L Jenkins
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC, Canada
| | - Jagoree Roy
- Department of Biology, Stanford University, Stanford, CA, USA
| | - Alexis Z L Shih
- Department of Medical Genetics, University of British Columbia, Vancouver, Canada
- Max-Delbrück Center for Molecular Medicine, Berlin, Germany
| | - Nicole St-Denis
- Lunenfeld-Tanenbaum Research Institute at Mount Sinai Hospital, University of Toronto, Toronto, Canada
- High-Fidelity Science Communications, Summerside, PE, Canada
| | - Gergo Gulyas
- Section on Molecular Signal Transduction, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - Tamas Balla
- Section on Molecular Signal Transduction, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - Anne-Claude Gingras
- Lunenfeld-Tanenbaum Research Institute at Mount Sinai Hospital, University of Toronto, Toronto, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada
| | - Péter Várnai
- Department of Physiology, Faculty of Medicine, Semmelweis University, Budapest, Hungary
| | - Elizabeth Conibear
- Department of Medical Genetics, University of British Columbia, Vancouver, Canada
| | - John E Burke
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC, Canada
- Department of Biochemistry, The University of British Columbia, Vancouver, BC, Canada
| | - Martha S Cyert
- Department of Biology, Stanford University, Stanford, CA, USA.
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Harris NJ, Jenkins ML, Dalwadi U, Fleming KD, Nam SE, Parson MAH, Yip CK, Burke JE. Biochemical Insight into Novel Rab-GEF Activity of the Mammalian TRAPPIII Complex. J Mol Biol 2021; 433:167145. [PMID: 34229011 DOI: 10.1016/j.jmb.2021.167145] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Revised: 06/25/2021] [Accepted: 06/30/2021] [Indexed: 11/28/2022]
Abstract
Transport Protein Particle complexes (TRAPP) are evolutionarily conserved regulators of membrane trafficking, with this mediated by their guanine nucleotide exchange factor (GEF) activity towards Rab GTPases. In metazoans evidence suggests that two different TRAPP complexes exist, TRAPPII and TRAPPIII. These two complexes share a common core of subunits, with complex specific subunits (TRAPPC9 and TRAPPC10 in TRAPPII and TRAPPC8, TRAPPC11, TRAPPC12, TRAPPC13 in TRAPPIII). TRAPPII and TRAPPIII have distinct specificity for GEF activity towards Rabs, with TRAPPIII acting on Rab1, and TRAPPII acting on Rab1 and Rab11. The molecular basis for how these complex specific subunits alter GEF activity towards Rab GTPases is unknown. Here we have used a combination of biochemical assays, hydrogen deuterium exchange mass spectrometry (HDX-MS) and electron microscopy to examine the regulation of TRAPPII and TRAPPIIII complexes in solution and on membranes. GEF assays revealed that TRAPPIII has GEF activity against Rab1 and Rab43, with no detectable activity against the other 18 Rabs tested. The TRAPPIII complex had significant differences in protein dynamics at the Rab binding site compared to TRAPPII, potentially indicating an important role of accessory subunits in altering the active site of TRAPP complexes. Both the TRAPPII and TRAPPIII complexes had enhanced GEF activity on lipid membranes, with HDX-MS revealing numerous conformational changes that accompany membrane association. HDX-MS also identified a membrane binding site in TRAPPC8. Collectively, our results provide insight into the functions of TRAPP complexes and how they can achieve Rab specificity.
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Affiliation(s)
- Noah J Harris
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia V8W 2Y2, Canada
| | - Meredith L Jenkins
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia V8W 2Y2, Canada
| | - Udit Dalwadi
- Life Sciences Institute, Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Kaelin D Fleming
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia V8W 2Y2, Canada
| | - Sung-Eun Nam
- Life Sciences Institute, Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Matthew A H Parson
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia V8W 2Y2, Canada
| | - Calvin K Yip
- Life Sciences Institute, Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - John E Burke
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia V8W 2Y2, Canada; Life Sciences Institute, Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada.
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