scholarly journals Regulation of Hook1-mediated endosomal sorting of clathrin-independent cargo by γ-taxilin

2021 ◽  
Author(s):  
Satoru Higashi ◽  
Tomohiko Makiyama ◽  
Hiroshi Sakane ◽  
Satoru Nogami ◽  
Hiromichi Shirataki
Keyword(s):  
Molecular Mechanism ◽  
Hela Cells ◽  
Terminal Region ◽  
Cellular Functions ◽  
Recycling Endosomes ◽  
Endosomal Sorting ◽  
Cargo Proteins ◽  
Tubular Formation

In clathrin-independent endocytosis, Hook1, a microtubule- and cargo-tethering protein, participates in sorting of cargo proteins such as CD98 and CD147 into recycling endosomes. However, the molecular mechanism that regulates Hook1-mediated endosomal sorting is not fully understood. Here, we found that γ-taxilin is a novel regulator of Hook1-mediated endosomal sorting. γ-Taxilin depletion promoted both CD98-positive tubular formation and CD98 recycling. Conversely, overexpression of γ-taxilin inhibited the CD98-positive tubular formation. Depletion of Hook1, or Rab10 or Rab22a (which are both involved in Hook1-mediated endosomal sorting), attenuated the effect of γ-taxilin depletion on the CD98-positive tubular formation. γ-Taxilin depletion promoted CD147-mediated spreading of HeLa cells, suggesting that γ-taxilin may be a pivotal player in various cellular functions in which Hook1-mediated cargo proteins are involved. γ-Taxilin bound to the C-terminal region of Hook1 and inhibited its interaction with CD98; the latter interaction is necessary for sorting CD98. We suggest that γ-taxilin negatively regulates the sorting of Hook1-mediated cargo proteins into recycling endosomes by interfering with the interactions between Hook1 and the cargo proteins.

scholarly journals The cryo-EM structure of the bacterial flagellum cap complex suggests a molecular mechanism for filament elongation

2019 ◽  
Author(s):  
Natalie S. Al-Otaibi ◽  
Aidan J. Taylor ◽  
Daniel P. Farrell ◽  
Svetomir B. Tzokov ◽  
Frank DiMaio ◽  
...  
Keyword(s):  
Molecular Mechanism ◽  
Campylobacter Jejuni ◽  
Bacterial Cell ◽  
Molecular Basis ◽  
Molecular Model ◽  
Molecular Motor ◽  
Terminal Region ◽  
Bacterial Flagellum ◽  
Filament Assembly ◽  
Oligomeric Assembly

AbstractThe bacterial flagellum is a remarkable molecular motor, present at the surface of many bacteria, whose primary function is to allow motility through the rotation of a long filament protruding from the bacterial cell. A cap complex, consisting of an oligomeric assembly of the protein FliD, is localized at the tip of the flagellum, and is essential for filament assembly, as well as adherence to surfaces in some bacteria. However, the structure of the intact cap complex, and the molecular basis for its interaction with the filament, remains elusive. Here we report the cryo-EM structure of the Campylobacter jejuni cap complex. This structure reveals that FliD is pentameric, with the N-terminal region of the protomer forming an unexpected extensive set of contacts across several subunits, that contribute to FliD oligomerization. We also demonstrate that the native C. jejuni flagellum filament is 11-stranded and propose a molecular model for the filament-cap interaction.

scholarly journals A TOCA/CDC-42/PAR/WAVE functional module required for retrograde endocytic recycling

2015 ◽  
Vol 112 (12) ◽  
pp. E1443-E1452 ◽  
Author(s):  
Zhiyong Bai ◽  
Barth D. Grant
Keyword(s):  
Functional Module ◽  
Small Gtpase ◽  
Recycling Endosome ◽  
Vesicle Budding ◽  
Recycling Endosomes ◽  
Physiological Importance ◽  
Golgi Transport ◽  
Early Endosomes ◽  
Cargo Proteins ◽  
Signaling Receptors

Endosome-to-Golgi transport is required for the function of many key membrane proteins and lipids, including signaling receptors, small-molecule transporters, and adhesion proteins. The retromer complex is well-known for its role in cargo sorting and vesicle budding from early endosomes, in most cases leading to cargo fusion with the trans-Golgi network (TGN). Transport from recycling endosomes to the TGN has also been reported, but much less is understood about the molecules that mediate this transport step. Here we provide evidence that the F-BAR domain proteins TOCA-1 and TOCA-2 (Transducer of Cdc42 dependent actin assembly), the small GTPase CDC-42 (Cell division control protein 42), associated polarity proteins PAR-6 (Partitioning defective 6) and PKC-3/atypical protein kinase C, and the WAVE actin nucleation complex mediate the transport of MIG-14/Wls and TGN-38/TGN38 cargo proteins from the recycling endosome to the TGN in Caenorhabditis elegans. Our results indicate that CDC-42, the TOCA proteins, and the WAVE component WVE-1 are enriched on RME-1–positive recycling endosomes in the intestine, unlike retromer components that act on early endosomes. Furthermore, we find that retrograde cargo TGN-38 is trapped in early endosomes after depletion of SNX-3 (a retromer component) but is mainly trapped in recycling endosomes after depletion of CDC-42, indicating that the CDC-42–associated complex functions after retromer in a distinct organelle. Thus, we identify a group of interacting proteins that mediate retrograde recycling, and link these proteins to a poorly understood trafficking step, recycling endosome-to-Golgi transport. We also provide evidence for the physiological importance of this pathway in WNT signaling.

scholarly journals TBC1D24 regulates recycling of clathrin-independent cargo proteins mediated by tubular recycling endosomes

2020 ◽  
Vol 528 (1) ◽  
pp. 220-226
Author(s):  
Nguyen Thi Kim Nguyen ◽  
Norihiko Ohbayashi ◽  
Yasunori Kanaho ◽  
Yuji Funakoshi
Keyword(s):  
Recycling Endosomes ◽  
Cargo Proteins

scholarly journals Inhibition of Transferrin Recycling and Endosome Tubulation by Phospholipase A2Antagonists

2001 ◽  
Vol 276 (50) ◽  
pp. 47361-47370 ◽  
Author(s):  
Paul de Figueiredo ◽  
Anne Doody ◽  
Renée S. Polizotto ◽  
Daniel Drecktrah ◽  
Salli Wood ◽  
...  
Keyword(s):  
Cell Surface ◽  
Molecular Mechanism ◽  
Golgi Complex ◽  
Broad Spectrum ◽  
Tubule Formation ◽  
Recycling Endosomes ◽  
Low Concentrations ◽  
A Cell ◽  
Recycling Pathway ◽  
Lines Of Evidence

We report here that a broad spectrum of phospholipase A2(PLA2) antagonists produce a concentration-dependent, differential block in the endocytic recycling pathway of transferrin (Tf) and Tf receptors (TfRs) but have no acute affect on Tf uptake from the cell surface. At low concentrations of antagonists (∼1 μm), Tf and TfR accumulated in centrally located recycling endosomes, whereas at higher concentrations (∼10 μm), Tf-TfR accumulated in peripheral sorting endosomes. Several independent lines of evidence suggest that this inhibition of recycling may result from the inhibition of tubule formation. First, BFA-stimulated endosome tubule formation was similarly inhibited by PLA2antagonists. Second, endocytosed tracers were found in larger spherical endosomes in the presence of PLA2antagonists. And third, endosome tubule formation in a cell-free, cytosol-dependent reconstitution system was equally sensitive PLA2antagonists. These results are consistent with the conclusion that endosome membrane tubules are formed by the action of a cytoplasmic PLA2and that PLA2-dependent tubules are involved in intracellular recycling of Tf and TfR. When taken together with previous studies on the Golgi complex, these results also indicate that an intracellular PLA2activity provides a novel molecular mechanism for inducing tubule formation from multiple organelles.

scholarly journals Identification of the Helicobacter pylori VacA Toxin Domain Active in the Cell Cytosol

1998 ◽  
Vol 66 (12) ◽  
pp. 6014-6016 ◽  
Author(s):  
Marina de Bernard ◽  
Daniela Burroni ◽  
Emanuele Papini ◽  
Rino Rappuoli ◽  
John Telford ◽  
...  
Keyword(s):  
Helicobacter Pylori ◽  
Hela Cells ◽  
Terminal Region ◽  
Endocytic Pathway ◽  
Amino Terminal ◽  
Toxin Molecule ◽  
Intracellular Activity ◽  
Cell Cytosol ◽  
C And N ◽  
Late Stages

ABSTRACT Cells exposed to Helicobacter pylori toxin VacA develop large vacuoles which originate from massive swelling of membranous compartments at late stages of the endocytic pathway. When expressed in the cytosol, VacA induces vacuolization as it does when added from outside. This and other evidence indicate that VacA is a toxin capable of entering the cell cytosol, where it displays its activity. In this study, we have used cytosolic expression to identify the portion of the toxin molecule responsible for the vacuolating activity. VacA mutants with deletions at the C and N termini were generated, and their activity was analyzed upon expression in HeLa cells. We found that the vacuolating activity of VacA resides in the amino-terminal region, the whole of which is required for its intracellular activity.

Molecular mechanism of inhibitory effects of C-phycocyanin combined with all-trans-retinoic acid on the growth of HeLa cells in vitro

Tumor Biology ◽  
2014 ◽  
Vol 35 (6) ◽  
pp. 5619-5628 ◽  
Author(s):  
Fan Yang ◽  
Bing Li ◽  
Xian-Ming Chu ◽  
Cong-Yi Lv ◽  
Ying-Jie Xu ◽  
...  
Keyword(s):  
Retinoic Acid ◽  
Molecular Mechanism ◽  
Hela Cells ◽  
Inhibitory Effects ◽  
Trans Retinoic Acid ◽  
All Trans Retinoic Acid

scholarly journals EPI64 interacts with Slp1/JFC1 to coordinate Rab8a and Arf6 membrane trafficking

2012 ◽  
Vol 23 (4) ◽  
pp. 701-715 ◽  
Author(s):  
David E. Hokanson ◽  
Anthony P. Bretscher
Keyword(s):  
Hela Cells ◽  
Membrane Trafficking ◽  
Binding Proteins ◽  
Cell Function ◽  
Terminal Region ◽  
Cytoskeletal Organization ◽  
Vacuole Formation ◽  
Gtp Binding ◽  
Distinctive Phenotype ◽  
In Cells

Cell function requires the integration of cytoskeletal organization and membrane trafficking. Small GTP-binding proteins are key regulators of these processes. We find that EPI64, an apical microvillar protein with a Tre-2/Bub2/Cdc16 (TBC) domain that stabilizes active Arf6 and has RabGAP activity, regulates Arf6-dependent membrane trafficking. Expression of EPI64 in HeLa cells induces the accumulation of actin-coated vacuoles, a distinctive phenotype seen in cells expressing constitutively active Arf6. Expression of EPI64 with defective RabGAP activity does not induce vacuole formation. Coexpression of Rab8a suppresses the vacuole phenotype induced by EPI64, and EPI64 expression lowers the level of Rab8-GTP in cells, strongly suggesting that EPI64 has GAP activity toward Rab8a. JFC1, an effector for Rab8a, colocalizes with and binds directly to a C-terminal region of EPI64. Together this region and the N-terminal TBC domain of EPI64 are required for the accumulation of vacuoles. Through analysis of mutants that uncouple JFC1 from either EPI64 or from Rab8-GTP, our data suggest a model in which EPI64 binds JFC1 to recruit Rab8a-GTP for deactivation by the RabGAP activity of EPI64. We propose that EPI64 regulates membrane trafficking both by stabilizing Arf6-GTP and by inhibiting the recycling of membrane through the tubular endosome by decreasing Rab8a-GTP levels.

scholarly journals Evidence for an interaction between Golli and STIM1 in store-operated calcium entry

2010 ◽  
Vol 430 (3) ◽  
pp. 453-460 ◽  
Author(s):  
Ciara M. Walsh ◽  
Mary K. Doherty ◽  
Alexei V. Tepikin ◽  
Robert D. Burgoyne
Keyword(s):  
Hela Cells ◽  
Underlying Mechanism ◽  
Binding Assays ◽  
Cellular Functions ◽  
Store Depletion ◽  
Store Operated Calcium Entry ◽  
Oligodendrocyte Precursor ◽  
Ca2 Channels

SOCCs (store-operated Ca2+ channels) are highly selective ion channels that are activated upon release of Ca2+ from intracellular stores to regulate a multitude of diverse cellular functions. It was reported previously that Golli-BG21, a member of the MBP (myelin basic protein) family of proteins, regulates SOCE (store-operated Ca2+ entry) in T-cells and oligodendrocyte precursor cells, but the underlying mechanism for this regulation is unknown. In the present study we have discovered that Golli can directly interact with the ER (endoplasmic reticulum) Ca2+-sensing protein STIM1 (stromal interaction molecule 1). Golli interacts with the C-terminal domain of STIM1 in both in vitro and in vivo binding assays and this interaction may be modulated by the intracellular Ca2+ concentration. Golli also co-localizes with full-length STIM1 and Orai1 complexes in HeLa cells following Ca2+ store depletion. Overexpression of Golli reduces SOCE in HeLa cells, but this inhibition is overcome by overexpressing STIM1. We therefore suggest that Golli binds to STIM1–Orai1 complexes to negatively regulate the activity of SOCCs.

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