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Szodorai E, Hevesi Z, Wagner L, Hökfelt TGM, Harkany T, Schnell R. A hydrophobic groove in secretagogin allows for alternate interactions with SNAP-25 and syntaxin-4 in endocrine tissues. Proc Natl Acad Sci U S A 2024; 121:e2309211121. [PMID: 38593081 PMCID: PMC11032447 DOI: 10.1073/pnas.2309211121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Accepted: 03/09/2024] [Indexed: 04/11/2024] Open
Abstract
Vesicular release of neurotransmitters and hormones relies on the dynamic assembly of the exocytosis/trans-SNARE complex through sequential interactions of synaptobrevins, syntaxins, and SNAP-25. Despite SNARE-mediated release being fundamental for intercellular communication in all excitable tissues, the role of auxiliary proteins modulating the import of reserve vesicles to the active zone, and thus, scaling repetitive exocytosis remains less explored. Secretagogin is a Ca2+-sensor protein with SNAP-25 being its only known interacting partner. SNAP-25 anchors readily releasable vesicles within the active zone, thus being instrumental for 1st phase release. However, genetic deletion of secretagogin impedes 2nd phase release instead, calling for the existence of alternative protein-protein interactions. Here, we screened the secretagogin interactome in the brain and pancreas, and found syntaxin-4 grossly overrepresented. Ca2+-loaded secretagogin interacted with syntaxin-4 at nanomolar affinity and 1:1 stoichiometry. Crystal structures of the protein complexes revealed a hydrophobic groove in secretagogin for the binding of syntaxin-4. This groove was also used to bind SNAP-25. In mixtures of equimolar recombinant proteins, SNAP-25 was sequestered by secretagogin in competition with syntaxin-4. Kd differences suggested that secretagogin could shape unidirectional vesicle movement by sequential interactions, a hypothesis supported by in vitro biological data. This mechanism could facilitate the movement of transport vesicles toward release sites, particularly in the endocrine pancreas where secretagogin, SNAP-25, and syntaxin-4 coexist in both α- and β-cells. Thus, secretagogin could modulate the pace and fidelity of vesicular hormone release by differential protein interactions.
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Affiliation(s)
- Edit Szodorai
- Division of Molecular and Cellular Neuroendocrinology, Department of Neuroscience, Biomedicum 7D, Karolinska Institutet, SolnaSE-17165, Sweden
- Department of Molecular Neurosciences, Center for Brain Research, Medical University of Vienna, ViennaA-1090, Austria
| | - Zsofia Hevesi
- Department of Molecular Neurosciences, Center for Brain Research, Medical University of Vienna, ViennaA-1090, Austria
| | - Ludwig Wagner
- Department of Internal Medicine III, Medical University of Vienna, ViennaA-1090, Austria
| | - Tomas G. M. Hökfelt
- Division of Molecular and Cellular Neuroendocrinology, Department of Neuroscience, Biomedicum 7D, Karolinska Institutet, SolnaSE-17165, Sweden
| | - Tibor Harkany
- Division of Molecular and Cellular Neuroendocrinology, Department of Neuroscience, Biomedicum 7D, Karolinska Institutet, SolnaSE-17165, Sweden
- Department of Molecular Neurosciences, Center for Brain Research, Medical University of Vienna, ViennaA-1090, Austria
| | - Robert Schnell
- Division of Molecular and Cellular Neuroendocrinology, Department of Neuroscience, Biomedicum 7D, Karolinska Institutet, SolnaSE-17165, Sweden
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Kulicke CA, Swarbrick GM, Ladd NA, Cansler M, Null M, Worley A, Lemon C, Ahmed T, Bennett J, Lust TN, Heisler CM, Huber ME, Krawic JR, Ankley LM, McBride SK, Tafesse FG, Olive AJ, Hildebrand WH, Lewinsohn DA, Adams EJ, Lewinsohn DM, Harriff MJ. Delivery of loaded MR1 monomer results in efficient ligand exchange to host MR1 and subsequent MR1T cell activation. Commun Biol 2024; 7:228. [PMID: 38402309 PMCID: PMC10894271 DOI: 10.1038/s42003-024-05912-4] [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: 11/14/2023] [Accepted: 02/12/2024] [Indexed: 02/26/2024] Open
Abstract
MR1-restricted T cells have been implicated in microbial infections, sterile inflammation, wound healing and cancer. Similar to other antigen presentation molecules, evidence supports multiple, complementary MR1 antigen presentation pathways. To investigate ligand exchange pathways for MR1, we used MR1 monomers and tetramers loaded with 5-(2-oxopropylideneamino)-6-d-ribitylaminouracil (5-OP-RU) to deliver the antigen. Using MR1-deficient cells reconstituted with wild-type MR1 or MR1 molecules that cannot bind 5-OP-RU, we show that presentation of monomer-delivered 5-OP-RU is dependent on cellular MR1 and requires the transfer of ligand from the soluble molecule onto MR1 expressed by the antigen presenting cell. This mode of antigen delivery strengthens the evidence for post-ER ligand exchange pathways for MR1, which could represent an important avenue by which MR1 acquires antigens derived from endocytosed pathogens.
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Affiliation(s)
- Corinna A Kulicke
- Division of Pulmonary, Allergy, and Critical Care Medicine, Oregon Health & Science University, Portland, OR, 97239, USA
| | - Gwendolyn M Swarbrick
- Division of Infectious Diseases, Department of Pediatrics, Oregon Health & Science University, Portland, OR, 97239, USA
| | - Nicole A Ladd
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, 60637, USA
| | - Meghan Cansler
- Division of Infectious Diseases, Department of Pediatrics, Oregon Health & Science University, Portland, OR, 97239, USA
| | - Megan Null
- Division of Infectious Diseases, Department of Pediatrics, Oregon Health & Science University, Portland, OR, 97239, USA
| | - Aneta Worley
- Division of Pulmonary, Allergy, and Critical Care Medicine, Oregon Health & Science University, Portland, OR, 97239, USA
| | - Chance Lemon
- Division of Pulmonary, Allergy, and Critical Care Medicine, Oregon Health & Science University, Portland, OR, 97239, USA
| | - Tania Ahmed
- Division of Infectious Diseases, Department of Pediatrics, Oregon Health & Science University, Portland, OR, 97239, USA
| | - Joshua Bennett
- Division of Infectious Diseases, Department of Pediatrics, Oregon Health & Science University, Portland, OR, 97239, USA
| | - Taylor N Lust
- Division of Pulmonary, Allergy, and Critical Care Medicine, Oregon Health & Science University, Portland, OR, 97239, USA
| | - Chelsea M Heisler
- Division of Pulmonary, Allergy, and Critical Care Medicine, Oregon Health & Science University, Portland, OR, 97239, USA
| | - Megan E Huber
- Department of Molecular Microbiology and Immunology, Oregon Health & Science University, Portland, OR, 97239, USA
| | - Jason R Krawic
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA
| | - Laurisa M Ankley
- Department of Microbiology and Molecular Genetics, College of Osteopathic Medicine, Michigan State University, East Lansing, MI, 48824, USA
| | - Savannah K McBride
- Department of Molecular Microbiology and Immunology, Oregon Health & Science University, Portland, OR, 97239, USA
| | - Fikadu G Tafesse
- Department of Molecular Microbiology and Immunology, Oregon Health & Science University, Portland, OR, 97239, USA
| | - Andrew J Olive
- Department of Microbiology and Molecular Genetics, College of Osteopathic Medicine, Michigan State University, East Lansing, MI, 48824, USA
| | - William H Hildebrand
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA
| | - Deborah A Lewinsohn
- Division of Infectious Diseases, Department of Pediatrics, Oregon Health & Science University, Portland, OR, 97239, USA
| | - Erin J Adams
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, 60637, USA
| | - David M Lewinsohn
- Division of Pulmonary, Allergy, and Critical Care Medicine, Oregon Health & Science University, Portland, OR, 97239, USA
- VA Portland Health Care System, Portland, OR, 97239, USA
| | - Melanie J Harriff
- Division of Pulmonary, Allergy, and Critical Care Medicine, Oregon Health & Science University, Portland, OR, 97239, USA.
- Department of Molecular Microbiology and Immunology, Oregon Health & Science University, Portland, OR, 97239, USA.
- VA Portland Health Care System, Portland, OR, 97239, USA.
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Jacopo M. Unconventional protein secretion (UPS): role in important diseases. MOLECULAR BIOMEDICINE 2023; 4:2. [PMID: 36622461 PMCID: PMC9827022 DOI: 10.1186/s43556-022-00113-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Accepted: 12/19/2022] [Indexed: 01/10/2023] Open
Abstract
Unconventional protein secretion (UPS) is the new secretion process discovered in liquid form over three decades ago. More recently, UPS has been shown to operate also in solid forms generated from four types of organelles: fractions of lysosomes and autophagy (APh) undergoing exocytosis; exosomes and ectosomes, with their extracellular vesicles (EVs). Recently many mechanisms and proteins of these solid forms have been shown to depend on UPS. An additional function of UPS is the regulation of diseases, often investigated separately from each other. In the present review, upon short presentation of UPS in healthy cells and organs, interest is focused on the mechanisms and development of diseases. The first reported are neurodegenerations, characterized by distinct properties. Additional diseases, including inflammasomes, inflammatory responses, glial effects and other diseases of various origin, are governed by proteins generated, directly or alternatively, by UPS. The diseases most intensely affected by UPS are various types of cancer, activated in most important processes: growth, proliferation and invasion, relapse, metastatic colonization, vascular leakiness, immunomodulation, chemoresistence. The therapy role of UPS diseases depends largely on exosomes. In addition to affecting neurodegenerative diseases, its special aim is the increased protection against cancer. Its immense relevance is due to intrinsic features, including low immunogenicity, biocompatibility, stability, and crossing of biological barriers. Exosomes, loaded with factors for pharmacological actions and target cell sensitivity, induce protection against various specific cancers. Further expansion of disease therapies is expected in the near future.
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Affiliation(s)
- Meldolesi Jacopo
- grid.18887.3e0000000417581884San Raffaele Institute, Vita-Salute San Raffaele University, Milan, Italy ,CNR Institute of Neuroscience at the Milano-Bicocca University, Milan, Italy
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Bracey KM, Gu G, Kaverina I. Microtubules in Pancreatic β Cells: Convoluted Roadways Toward Precision. Front Cell Dev Biol 2022; 10:915206. [PMID: 35874834 PMCID: PMC9305484 DOI: 10.3389/fcell.2022.915206] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Accepted: 06/14/2022] [Indexed: 11/18/2022] Open
Abstract
Pancreatic islet β cells regulate glucose homeostasis via glucose-stimulated insulin secretion (GSIS). Cytoskeletal polymers microtubules (MTs) serve as tracks for the transport and positioning of secretory insulin granules. MT network in β cells has unique morphology with several distinct features, which support granule biogenesis (via Golgi-derived MT array), net non-directional transport (via interlocked MT mesh), and control availability of granules at secretion sites (via submembrane MT bundle). The submembrane MT array, which is parallel to the plasma membrane and serves to withdraw excessive granules from the secretion hot spots, is destabilized and fragmented downstream of high glucose stimulation, allowing for regulated secretion. The origin of such an unusual MT network, the features that define its functionality, and metabolic pathways that regulate it are still to a large extent elusive and are a matter of active investigation and debate. Besides the MT network itself, it is important to consider the interplay of molecular motors that drive and fine-tune insulin granule transport. Importantly, activity of kinesin-1, which is the major MT-dependent motor in β cells, transports insulin granules, and has a capacity to remodel MT network, is also regulated by glucose. We discuss yet unknown potential avenues toward understanding how MT network and motor proteins provide control for secretion in coordination with other GSIS-regulating mechanisms.
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