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Overduin M, Bhat R. Recognition and remodeling of endosomal zones by sorting nexins. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2024; 1866:184305. [PMID: 38408696 DOI: 10.1016/j.bbamem.2024.184305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2023] [Revised: 02/05/2024] [Accepted: 02/18/2024] [Indexed: 02/28/2024]
Abstract
The proteolipid code determines how cytosolic proteins find and remodel membrane surfaces. Here, we investigate how this process works with sorting nexins Snx1 and Snx3. Both proteins form sorting machines by recognizing membrane zones enriched in phosphatidylinositol 3-phosphate (PI3P), phosphatidylserine (PS) and cholesterol. This co-localized combination forms a unique "lipid codon" or lipidon that we propose is responsible for endosomal targeting, as revealed by structures and interactions of their PX domain-based readers. We outline a membrane recognition and remodeling mechanism for Snx1 and Snx3 involving this code element alongside transmembrane pH gradients, dipole moment-guided docking and specific protein-protein interactions. This generates an initial membrane-protein assembly (memtein) that then recruits retromer and additional PX proteins to recruit cell surface receptors for sorting to the trans-Golgi network (TGN), lysosome and plasma membranes. Post-translational modification (PTM) networks appear to regulate how the sorting machines form and operate at each level. The commonalities and differences between these sorting nexins show how the proteolipid code orchestrates parallel flows of molecular information from ribosome emergence to organelle genesis, and illuminates a universally applicable model of the membrane.
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Affiliation(s)
- Michael Overduin
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada.
| | - Rakesh Bhat
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada
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Utsumi T, Matsuzaki K, Kiwado A, Tanikawa A, Kikkawa Y, Hosokawa T, Otsuka A, Iuchi Y, Kobuchi H, Moriya K. Identification and characterization of protein N-myristoylation occurring on four human mitochondrial proteins, SAMM50, TOMM40, MIC19, and MIC25. PLoS One 2018; 13:e0206355. [PMID: 30427857 PMCID: PMC6235283 DOI: 10.1371/journal.pone.0206355] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2018] [Accepted: 10/11/2018] [Indexed: 11/29/2022] Open
Abstract
Previously, we showed that SAMM50, a mitochondrial outer membrane protein, is N-myristoylated, and this lipid modification is required for the proper targeting of SAMM50 to mitochondria. In this study, we characterized protein N-myristoylation occurring on four human mitochondrial proteins, SAMM50, TOMM40, MIC19, and MIC25, three of which are components of the mitochondrial intermembrane space bridging (MIB) complex, which plays a critical role in the structure and function of mitochondria. In vitro and in vivo metabolic labeling experiments revealed that all four of these proteins were N-myristoylated. Analysis of intracellular localization of wild-type and non-myristoylated G2A mutants of these proteins by immunofluorescence microscopic analysis and subcellular fractionation analysis indicated that protein N-myristoylation plays a critical role in mitochondrial targeting and membrane binding of two MIB components, SAMM50 and MIC19, but not those of TOMM40 and MIC25. Immunoprecipitation experiments using specific antibodies revealed that MIC19, but not MIC25, was a major N-myristoylated binding partner of SAMM50. Immunoprecipitation experiments using a stable transformant of MIC19 confirmed that protein N-myristoylation of MIC19 is required for the interaction between MIC19 and SAMM50, as reported previously. Thus, protein N-myristoylation occurring on two mitochondrial MIB components, SAMM50 and MIC19, plays a critical role in the mitochondrial targeting and protein-protein interaction between these two MIB components.
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Affiliation(s)
- Toshihiko Utsumi
- Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Yamaguchi, Japan.,Department of Biological Chemistry, Faculty of Agriculture, Yamaguchi University, Yamaguchi, Japan
| | - Kanako Matsuzaki
- Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Yamaguchi, Japan
| | - Aya Kiwado
- Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Yamaguchi, Japan
| | - Ayane Tanikawa
- Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Yamaguchi, Japan
| | - Yuki Kikkawa
- Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Yamaguchi, Japan
| | - Takuro Hosokawa
- Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Yamaguchi, Japan
| | - Aoi Otsuka
- Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Yamaguchi, Japan
| | - Yoshihito Iuchi
- Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Yamaguchi, Japan
| | - Hirotsugu Kobuchi
- Department of Cell Chemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan
| | - Koko Moriya
- Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Yamaguchi, Japan
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