Dataset Information

Arfaptin-1 negatively regulates Arl1-mediated retrograde transport.

ABSTRACT: The small GTPase Arf-like protein 1 (Arl1) is well known for its role in intracellular vesicular transport at the trans-Golgi network (TGN). In this study, we used differential affinity chromatography combined with mass spectrometry to identify Arf-interacting protein 1b (arfaptin-1b) as an Arl1-interacting protein and characterized a novel function for arfaptin-1 (including the arfaptin-1a and 1b isoforms) in Arl1-mediated retrograde transport. Using a Shiga-toxin subunit B (STxB) transportation assay, we demonstrated that knockdown of arfaptin-1 accelerated the retrograde transport of STxB from the endosome to the Golgi apparatus, whereas Arl1 knockdown inhibited STxB transport compared with control cells. Arfaptin-1 overexpression, but not an Arl1 binding-defective mutant (arfaptin-1b-F317A), consistently inhibited STxB transport. Exogenous arfaptin-1 expression did not interfere with the localization of the Arl1-interacting proteins golgin-97 and golgin-245 to the TGN and vice versa. Moreover, we found that the N-terminal region of arfaptin-1 was involved in the regulation of retrograde transport. Our results show that arfaptin-1 acts as a negative regulator in Arl1-mediated retrograde transport and suggest that different functional complexes containing Arl1 form in distinct microdomains and are responsible for different functions.

SUBMITTER: Huang LH

PROVIDER: S-EPMC4366199 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Arfaptin-1 negatively regulates Arl1-mediated retrograde transport.

Huang Lien-Hung LH Lee Wei-Chung WC You Shu-Ting ST Cheng Chia-Chen CC Yu Chia-Jung CJ

PloS one 20150319 3

The small GTPase Arf-like protein 1 (Arl1) is well known for its role in intracellular vesicular transport at the trans-Golgi network (TGN). In this study, we used differential affinity chromatography combined with mass spectrometry to identify Arf-interacting protein 1b (arfaptin-1b) as an Arl1-interacting protein and characterized a novel function for arfaptin-1 (including the arfaptin-1a and 1b isoforms) in Arl1-mediated retrograde transport. Using a Shiga-toxin subunit B (STxB) transportatio ...[more]

PMID: 25789876

Similar Datasets

Project description:Ricin is a member of the ubiquitous family of plant and bacterial AB toxins that gain entry into the cytosol of host cells through receptor-mediated endocytosis and retrograde traffic through the trans-Golgi network (TGN) and endoplasmic reticulum (ER). While a few ricin toxin-specific neutralizing monoclonal antibodies (MAbs) have been identified, the mechanisms by which these antibodies prevent toxin-induced cell death are largely unknown. Using immunofluorescence confocal microscopy and a TGN-specific sulfation assay, we demonstrate that 24B11, a MAb against ricin's binding subunit (RTB), associates with ricin in solution or when prebound to cell surfaces and then markedly enhances toxin uptake into host cells. Following endocytosis, however, toxin-antibody complexes failed to reach the TGN; instead, they were shunted to Rab7-positive late endosomes and LAMP-1-positive lysosomes. Monovalent 24B11 Fab fragments also interfered with toxin retrograde transport, indicating that neither cross-linking of membrane glycoproteins/glycolipids nor the recently identified intracellular Fc receptor is required to derail ricin en route to the TGN. Identification of the mechanism(s) by which antibodies like 24B11 neutralize ricin will advance our fundamental understanding of protein trafficking in mammalian cells and may lead to the discovery of new classes of toxin inhibitors and therapeutics for biodefense and emerging infectious diseases. IMPORTANCE Ricin is the prototypic member of the AB family of medically important plant and bacterial toxins that includes cholera and Shiga toxins. Ricin is also a category B biothreat agent. Despite ongoing efforts to develop vaccines and antibody-based therapeutics against ricin, very little is known about the mechanisms by which antibodies neutralize this toxin. In general, it is thought that antibodies simply prevent toxins from attaching to cell surface receptors or promote their clearance through Fc receptor (FcR)-mediated uptake. In this report, however, we describe a neutralizing monoclonal antibody (MAb) against ricin's binding subunit (RTB) that not only associates with ricin after the toxin has bound to the cell's surface but actually enhances toxin uptake into host cells. Following endocytosis, the antibody-toxin complexes are then routed for degradation. The results of this study are important because they reveal a previously unappreciated role for B-subunit-specific antibodies in intracellular neutralization of ricin toxin.

Project description:The p53 homologue, p63, is critical for normal epidermal development. While overexpression of deltaNp63alpha has been reported in squamous cell cancers, the contribution of p63 to cancer pathogenesis remains unclear. We previously demonstrated that overexpressed deltaNp63alpha aberrantly maintains proliferation of primary epidermal keratinocytes under conditions that normally induce growth arrest and differentiation. To identify target genes impacted by dysregulated deltaNp63alpha that may contribute to squamous cancer development and progression, microarray analyses were performed. Herein we report that elevated deltaNp63alpha differentially regulates genes in primary mouse keratinocytes involved in a variety of cellular functions, including cell cycle regulation, differentiation, skin barrier formation and function, apoptosis, host defense/inflammation, adhesion, migration and invasion. Of note, multiple protease inhibitor mRNAs were coordinately downregulated under both proliferating and differentiating culture conditions. These downregulated genes include two serine protease inhibitors: maspin (serpinB5) and plasminogen activator inhibitor-2 (PAI-2; serpinB2), as well as a tissue inhibitor of metalloproteinase-3 (TIMP-3). Correspondingly, secreted levels of TIMP-3 and PAI-2 protein declined in the presence of dysregulated deltaNp63alpha, while secreted maspin protein levels remained stable. Intracellular maspin protein expression decreased in response to overexpressed deltaNp63alpha, as did intracellular PAI-2. Unlike PAI-2 and maspin, TIMP-3 protein was not detected intracellularly in control or deltaNp63alpha-overexpressing keratinocytes, supporting a solely extracellular function for TIMP-3. Electrophoretic mobility shift assays using a p53/p63 consensus DNA binding sequence from the maspin promoter revealed binding of an endogenous transcription factor(s) to the consensus sequence in normal keratinocytes that was disrupted by overexpressed deltaNp63alpha. This binding was also interrupted by the addition of a p73 antibody, but not antibodies to p63 or p53, and was absent in samples derived from p73(-/-) keratinocytes, confirming p73 as a constituent of the endogenous transcription factor complex. These data suggest protease inhibitors as novel targets of dysregulated deltaNp63alpha in cancer pathogenesis. Keratinocytes were transduced with adenoviruses encoding deltaNp63alpha. Keratinocytes were either maintained in low calcium conditions (0.05 mM for 24 hours) (n=6) or high calcium conditions (0.12 mM for 24 hours) (n=6). Control samples consisted of keratinocytes transduced with adenoviruses encoding beta-galactosidase also treated with low calcium (n=6) and high calcium (n=6) conditions. Twelve technical repeat microarray experiments were conducted, pairing high-calcium deltaNp63alpha samples with high-calcium beta-galactosidase samples (n=6) and low-calcium deltaNp63alpha samples with low-calcium beta-galactosidase samples (n=6). Six of the technical repeats were conducted as reverse-fluoro experiments.

Dataset Information

Arfaptin-1 negatively regulates Arl1-mediated retrograde transport.

Publications

Arfaptin-1 negatively regulates Arl1-mediated retrograde transport.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets