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Roach TG, Lång HKM, Xiong W, Ryhänen SJ, Capelluto DGS. Protein Trafficking or Cell Signaling: A Dilemma for the Adaptor Protein TOM1. Front Cell Dev Biol 2021; 9:643769. [PMID: 33718385 PMCID: PMC7952518 DOI: 10.3389/fcell.2021.643769] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Accepted: 02/09/2021] [Indexed: 12/29/2022] Open
Abstract
Lysosomal degradation of ubiquitinated transmembrane protein receptors (cargo) relies on the function of Endosomal Sorting Complex Required for Transport (ESCRT) protein complexes. The ESCRT machinery is comprised of five unique oligomeric complexes with distinct functions. Target of Myb1 (TOM1) is an ESCRT protein involved in the initial steps of endosomal cargo sorting. To exert its function, TOM1 associates with ubiquitin moieties on the cargo via its VHS and GAT domains. Several ESCRT proteins, including TOLLIP, Endofin, and Hrs, have been reported to form a complex with TOM1 at early endosomal membrane surfaces, which may potentiate the role of TOM1 in cargo sorting. More recently, it was found that TOM1 is involved in other physiological processes, including autophagy, immune responses, and neuroinflammation, which crosstalk with its endosomal cargo sorting function. Alteration of TOM1 function has emerged as a phosphoinositide-dependent survival mechanism for bacterial infections and cancer progression. Based on current knowledge of TOM1-dependent cellular processes, this review illustrates how TOM1 functions in coordination with an array of protein partners under physiological and pathological scenarios.
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Affiliation(s)
- Tiffany G. Roach
- Protein Signaling Domains Laboratory, Department of Biological Sciences, Fralin Life Sciences Institute, and Center for Soft Matter and Biological Physics, Virginia Tech, Blacksburg, VA, United States
| | - Heljä K. M. Lång
- Division of Hematology, Oncology, and Stem Cell Transplantation, Children’s Hospital, and Pediatric Research Center, The New Children’s Hospital, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
- Department of Anatomy and Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Wen Xiong
- Protein Signaling Domains Laboratory, Department of Biological Sciences, Fralin Life Sciences Institute, and Center for Soft Matter and Biological Physics, Virginia Tech, Blacksburg, VA, United States
| | - Samppa J. Ryhänen
- Division of Hematology, Oncology, and Stem Cell Transplantation, Children’s Hospital, and Pediatric Research Center, The New Children’s Hospital, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
| | - Daniel G. S. Capelluto
- Protein Signaling Domains Laboratory, Department of Biological Sciences, Fralin Life Sciences Institute, and Center for Soft Matter and Biological Physics, Virginia Tech, Blacksburg, VA, United States
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Xiong W, Tang TX, Littleton E, Karcini A, Lazar IM, Capelluto DGS. Preferential phosphatidylinositol 5-phosphate binding contributes to a destabilization of the VHS domain structure of Tom1. Sci Rep 2019; 9:10868. [PMID: 31350523 PMCID: PMC6659632 DOI: 10.1038/s41598-019-47386-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Accepted: 07/16/2019] [Indexed: 12/21/2022] Open
Abstract
Tom1 transports endosomal ubiquitinated proteins that are targeted for degradation in the lysosomal pathway. Infection of eukaryotic cells by Shigella flexneri boosts oxygen consumption and promotes the synthesis of phosphatidylinositol-5-phosphate (PtdIns5P), which triggers Tom1 translocation to signaling endosomes. Removing Tom1 from its cargo trafficking function hinders protein degradation in the host and, simultaneously, enables bacterial survival. Tom1 preferentially binds PtdIns5P via its VHS domain, but the effects of a reducing environment as well as PtdIns5P on the domain structure and function are unknown. Thermal denaturation studies demonstrate that, under reducing conditions, the monomeric Tom1 VHS domain switches from a three-state to a two-state transition behavior. PtdIns5P reduced thermostability, interhelical contacts, and conformational compaction of Tom1 VHS, suggesting that the phosphoinositide destabilizes the protein domain. Destabilization of Tom1 VHS structure was also observed with other phospholipids. Isothermal calorimetry data analysis indicates that, unlike ubiquitin, Tom1 VHS endothermically binds to PtdIns5P through two noncooperative binding sites, with its acyl chains playing a relevant role in the interaction. Altogether, these findings provide mechanistic insights about the recognition of PtdIns5P by the VHS domain that may explain how Tom1, when in a different VHS domain conformational state, interacts with downstream effectors under S. flexneri infection.
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Affiliation(s)
- Wen Xiong
- Protein Signaling Domains Laboratory, Department of Biological Sciences, Fralin Life Sciences Institute, and Center for Soft Matter and Biological Physics, Virginia Tech, Blacksburg, VA, 24061, United States
| | - Tuo-Xian Tang
- Protein Signaling Domains Laboratory, Department of Biological Sciences, Fralin Life Sciences Institute, and Center for Soft Matter and Biological Physics, Virginia Tech, Blacksburg, VA, 24061, United States
| | - Evan Littleton
- Protein Signaling Domains Laboratory, Department of Biological Sciences, Fralin Life Sciences Institute, and Center for Soft Matter and Biological Physics, Virginia Tech, Blacksburg, VA, 24061, United States
| | - Arba Karcini
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, 24061, United States
| | - Iulia M Lazar
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, 24061, United States
| | - Daniel G S Capelluto
- Protein Signaling Domains Laboratory, Department of Biological Sciences, Fralin Life Sciences Institute, and Center for Soft Matter and Biological Physics, Virginia Tech, Blacksburg, VA, 24061, United States.
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Ellena JF, Xiong W, Zhao X, Shanaiah N, Capelluto DGS. Backbone 1H, 15N, and 13C resonance assignments of the Tom1 VHS domain. BIOMOLECULAR NMR ASSIGNMENTS 2017; 11:1-4. [PMID: 27704363 DOI: 10.1007/s12104-016-9709-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Accepted: 09/29/2016] [Indexed: 06/06/2023]
Abstract
Efficient trafficking of ubiquitinated receptors (cargo) to endosomes requires the recruitment of adaptor proteins that exhibit ubiquitin-binding domains for recognition and transport. Tom1 is an adaptor protein that not only associates with ubiquitinated cargo but also represents a phosphoinositide effector during specific bacterial infections. This phosphoinositide-binding property is associated with its N-terminal Vps27, Hrs, STAM (VHS) domain. Despite its biological relevance, there are no resonance assignments of Tom1 VHS available that can fully characterize its molecular interactions. Here, we report the nearly complete 1H, 15N, and 13C backbone resonance assignments of the VHS domain of human Tom1.
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Affiliation(s)
- Jeffrey F Ellena
- Biomolecular Magnetic Resonance Facility, University of Virginia, Charlottesville, VA, 22904, USA
| | - Wen Xiong
- Protein Signaling Domains Laboratory, Department of Biological Sciences, Biocomplexity Institute and Center for Soft Matter and Biological Physics, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Xiaolin Zhao
- Protein Signaling Domains Laboratory, Department of Biological Sciences, Biocomplexity Institute and Center for Soft Matter and Biological Physics, Virginia Tech, Blacksburg, VA, 24061, USA
| | | | - Daniel G S Capelluto
- Protein Signaling Domains Laboratory, Department of Biological Sciences, Biocomplexity Institute and Center for Soft Matter and Biological Physics, Virginia Tech, Blacksburg, VA, 24061, USA.
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