Search results for "Vesicular Transport"
showing 10 items of 55 documents
Loss of endocytic clathrin-coated pits upon acute depletion of phosphatidylinositol 4,5-bisphosphate.
2007
Phosphatidylinositol 4,5-bisphosphate [PI(4,5) P 2 ], a phosphoinositide concentrated predominantly in the plasma membrane, binds endocytic clathrin adaptors, many of their accessory factors, and a variety of actin-regulatory proteins. Here we have used fluorescent fusion proteins and total internal reflection fluorescence microscopy to investigate the effect of acute PI(4,5) P 2 breakdown on the dynamics of endocytic clathrin-coated pit components and of the actin regulatory complex, Arp2/3. PI(4,5) P 2 breakdown was achieved by the inducible recruitment to the plasma membrane of an inositol 5-phosphatase module through the rapamycin/FRB/FKBP system or by treatment with ionomycin. PI(4,5)…
The Co‐mutational Spectrum Determines the Therapeutic Response in Murine FGFR2 Fusion‐Driven Cholangiocarcinoma
2021
Background and aims Intrahepatic cholangiocarcinoma (ICC) is the second most common primary liver cancer and a highly lethal malignancy. Chemotherapeutic options are limited, but a considerable subset of patients harbors genetic lesions for which targeted agents exist. Fibroblast growth factor receptor 2 (FGFR2) fusions belong to the most frequent and therapeutically relevant alterations in ICC, and the first FGFR inhibitor was recently approved for the treatment of patients with progressed, fusion-positive ICC. Response rates of up to 35% indicate that FGFR-targeted therapies are beneficial in many but not all patients. Thus far, no established biomarkers exist that predict resistance or r…
Mapping the protein composition oftrans-Golgi network (TGN)-derived carrier vesicles from polarized MDCK cells
1998
In polarized MDCK cells, proteins and lipids are sorted in the trans-Golgi network /TGN) and packaged into different vesicular carriers that are delivered to the apical or basolateral cell surface. To gain insight into the sorting and trafficking machinery, we have previously isolated TGN-derived carrier vesicles from perforated MDCK cells. The composition of immuno-isolated apical and basolateral carriers was mapped by two-dimensional (2-D) gel electrophoresis. Here we describe the identification of several components of the vesicle fraction by using three different methods. 2-D gel comigration was performed with carrier vesicles isolated from metabolically labeled MDCK cells and human epi…
Identification of novel interaction partners for Vlgr1b/GPR98 - a key component of the periciliary Usher syndrome protein network in photoreceptor ce…
2012
The human Usher syndrome (USH) is the most common form of combined hereditary deaf-blindness. Three clinical subtypes (USH1-3) are differentiated based on severity, age of onset and progression of the symptoms. Mutations in the GPR98 gene encoding the USH2C protein Vlgr1b or GPR98 cause USH2, the most common form of USH. The G-protein coupled receptor Vlgr1b was previously identified as a component of the periciliary USH protein network, crucial for ciliary cargo transport in photoreceptors. Nonetheless, the exact role of Vlgr1b in this and other cellular processes remains to be elucidated. To learn more about its involvement in cellular functions we searched for novel interaction partners …
Cohen syndrome is associated with major glycosylation defects
2014
International audience; Cohen syndrome (CS) is a rare autosomal recessive disorder with multisytemic clinical features due to mutations in the VPS13B gene, which has recently been described encoding a mandatory membrane protein involved in Golgi integrity. As the Golgi complex is the place where glycosylation of newly synthesized proteins occurs, we hypothesized that VPS13B deficiency, responsible of Golgi apparatus disturbance, could lead to glycosylation defects and/or mysfunction of this organelle, and thus be a cause of the main clinical manifestations of CS. The glycosylation status of CS serum proteins showed a very unusual pattern of glycosylation characterized by a significant accum…
Hepatitis B subviral envelope particles use the COPII machinery for intracellular transport via selective exploitation of Sec24A and Sec23B
2020
Hepatitis B virus (HBV) is a leading cause of liver disease. Its success as a human pathogen is related to the immense production of subviral envelope particles (SVPs) contributing to viral persistence by interfering with immune functions. To explore cellular pathways involved in SVP formation and egress, we investigated host-pathogen interactions. Yeast-based proteomics revealed Sec24A, a component of the coat protein complex II (COPII), as an interaction partner of the HBV envelope S domain. To understand how HBV co-opts COPII as a proviral machinery, we studied roles of key Sec proteins in HBV-expressing liver cells. Silencing of Sar1, Sec23, and Sec24, which promote COPII assembly conco…
Hepatitis B virus maturation is sensitive to functional inhibition of ESCRT-III, Vps4, and gamma 2-adaptin.
2007
ABSTRACT Hepatitis B virus (HBV) is an enveloped DNA virus that presumably buds at intracellular membranes of infected cells. HBV budding involves two endocytic host proteins, the ubiquitin-interacting adaptor γ2-adaptin and the Nedd4 ubiquitin ligase. Here, we demonstrate that HBV release also requires the cellular machinery that generates internal vesicles of multivesicular bodies (MVBs). In order to perturb the MVB machinery in HBV-replicating liver cells, we used ectopic expression of dominant-negative mutants of different MVB components, like the ESCRT-III complex-forming CHMP proteins and the Vps4 ATPases. Upon coexpression of mutated CHMP3, CHMP4B, or CHMP4C forms, as well as of ATPa…
The Complex Regulatory Role of Cytomegalovirus Nuclear Egress Protein pUL50 in the Production of Infectious Virus
2021
The regulation of the nucleocytoplasmic release of herpesviral capsids is defined by the process of nuclear egress. Due to their large size, nuclear capsids are unable to traverse via nuclear pores, so that herpesviruses evolved to develop a vesicular transport pathway mediating their transition through both leaflets of the nuclear membrane. This process involves regulatory proteins, which support the local distortion of the nuclear envelope. For human cytomegalovirus (HCMV), the nuclear egress complex (NEC) is determined by the pUL50-pUL53 core that initiates multicomponent assembly with NEC-associated proteins and capsids. Hereby, pUL50 serves as a multi-interacting determinant that recru…
Adaptive suppression of the ATF4–CHOP branch of the unfolded protein response by toll-like receptor signalling
2009
The endoplasmic reticulum (ER) unfolded protein response (UPR) restores equilibrium to the ER, but prolonged expression of the UPR effector CHOP (GADD153) is cytotoxic. We found that CHOP expression induced by ER stress was suppressed by prior engagement of toll-like receptor (TLR) 3 or 4 through a TRIF-dependent pathway. TLR engagement did not suppress phosphorylation of PERK or eIF-2alpha, which are upstream of CHOP, but phospho-eIF-2alpha failed to promote translation of the CHOP activator ATF4. In mice subjected to systemic ER stress, pretreatment with low dose lipopolysaccharide (LPS), a TLR4 ligand, suppressed CHOP expression and apoptosis in splenic macrophages, renal tubule cells an…
Release of IL-12 by dendritic cells activated by TLR ligation is dependent on MyD88 signaling, whereas TRIF signaling is indispensable for TLR synerg…
2010
Abstract Synergistic activation of dendritic cells by combinations of TLR ligands requires both MyD88- and TRIF-dependent signaling. Recently, it has been shown that certain combinations of TLR ligands act in synergy to induce the release of IL-12 by DCs. In this study, we sought to define the critical parameters underlying TLR synergy. Our data show that TLR ligands act synergistically if MyD88- and TRIF-dependent ligands are combined. TLR4 uses both of these adaptor molecules, thus activation via TLR4 proved to be a synergistic event on its own. TLR synergy did not affect all aspects of DC activation but enhanced primarily the release of certain cytokines, particularly IL-12, whereas the …