Biology subjects

Iguchi, M.

Publications and source records attributed to Iguchi, M..

3 recordsLinked to original sources

bioRxiv2024

ER sensing of lipid metabolism drives PRA family-dependent regulation of COPII vesicle transport

Newly synthesized secretory proteins and many lipids are transported from the endoplasmic reticulum (ER) to the Golgi prior to their ultimate destinations. The ER-to-Golgi transport must be tightly regulated during adaptation to environmental stress. However, the sensing mechanism and regulatory pathways governing the consecutive formation, budding and transportation of COPII vesicles from the ER remain insufficiently explored. Here, we present evidence indicating that COPII-mediated vesicle transport is transcriptionally controlled through the phosphatidic acid-dependent Opi1-Ino2/Ino4 regulatory circuit. Our analysis indicates that YIP3, a target gene of Ino2/Ino4, exerts a negative regulatory impact on COPII-mediated vesicle transport. Furthermore, we demonstrated that Ino2/Ino4 but not Yip3 modulates Sar1 activation, the initial step in COPII vesicle formation, whereas Yip3 hinders Sec16 assembly on the ER membrane, thereby implying that Ino2/Ino4 governs COPII-mediated trafficking at multiple steps. Thus, this study provides the first evidence for an ER sensing system that transcriptionally fine-tunes multiple steps of anterograde vesicular transport in response to alterations in lipid composition of the ER membrane.

cell biology↗

bioRxiv2023

MFSD1 in complex with its accessory subunit GLMP functions as a general dipeptide uniporter in lysosomes

Lysosomal degradation of macromolecules in lysosomes produces diverse small metabolites exported by specific transporters for reuse in biosynthetic pathways. Here, we deorphanized the Major Facilitator Superfamily Domain Containing 1 (MFSD1) protein, which forms a tight complex with the Glycosylated Lysosomal Membrane Protein (GLMP) in the lysosomal membrane. Untargeted metabolomics analysis of MFSD1-deficient mouse lysosomes revealed an increase in cationic dipeptides. Purified MFSD1 selectively bound diverse dipeptides, while electrophysiological, isotope tracer, and fluorescence-based studies in Xenopus oocytes and proteoliposomes showed that MFSD1/GLMP acts as a uniporter for cationic and neutral dipeptides. Cryo-EM structure of the dipeptide-bound MFSD1/GLMP complex in outward-open conformation characterized the heterodimer interface and, in combination with molecular dynamics simulations, provided a structural basis for its selectivity towards diverse dipeptides. Together, our data identify MFSD1 as a general lysosomal dipeptide uniporter, providing an alternative route to recycle lysosomal proteolysis products when lysosomal amino acid exporters are overloaded.

biochemistry↗

bioRxiv2022

Golgi-IP, a novel tool for multimodal analysis of Golgi molecular content

The Golgi is a membrane-bound organelle that is essential for protein and lipid biosynthesis. It represents a central trafficking hub that sorts proteins and lipids to various destinations or for secretion from the cell. The Golgi has emerged as a docking platform for cellular signalling pathways including LRRK2 kinase whose deregulation leads to Parkinson disease. Golgi dysfunction is associated with a broad spectrum of diseases including cancer, neurodegeneration, and cardiovascular diseases. To allow the study of the Golgi at high resolution, we report a rapid immunoprecipitation technique (Golgi-IP) to isolate intact Golgi mini-stacks for subsequent analysis of their content. By fusing the Golgi resident protein TMEM115 to three tandem HA epitopes (GolgiTAG), we purified the Golgi using Golgi-IP with minimal contamination from other compartments. We then established an analysis pipeline using liquid chromatography coupled with mass spectrometry to characterize the human Golgi proteome, metabolome and lipidome. Subcellular proteomics confirmed known Golgi proteins and identified novel ones. Metabolite profiling established the first known human Golgi metabolome and revealed the selective enrichment of uridine-diphosphate (UDP) sugars and their derivatives, which is consistent with their roles in protein and lipid glycosylation. Furthermore, targeted metabolomics validated SLC35A2 as the subcellular transporter for UDP-hexose. Finally, lipidomics analysis showed that phospholipids including phosphatidylcholine, phosphatidylinositol and phosphatidylserine are the most abundant Golgi lipids and that glycosphingolipids are enriched in this compartment. Altogether, our work establishes a comprehensive molecular map of the human Golgi and provides a powerful method to study the Golgi with high precision in health and disease states. SignificanceThe Golgi is central to protein and lipid processing. It senses and responds to diverse cell states to allow trafficking of macromolecules based on cellular demands. Traditional techniques for purifying the Golgi shaped our understanding of its functions, however such methods are too slow to preserve the labile Golgi metabolome and transient protein interactions. Here, we overcome this issue through the development of a method for the rapid capture of intact Golgi from human cells using organelle-specific immunoprecipitation (Golgi-IP). Using high resolution mass spectrometry, we demonstrate that our approach allows the unbiased characterization of the Golgi proteome, metabolome and lipidome. Thus, we believe that the Golgi-IP will be useful for the study of the Golgi in health and disease states.

cell biology↗