scholarly journals Sorting Nexin 17 Accelerates Internalization Yet Retards Degradation of P-selectin

2004 ◽  
Vol 15 (7) ◽  
pp. 3095-3105 ◽  
Author(s):  
Ross Williams ◽  
Thomas Schlüter ◽  
Marnie S. Roberts ◽  
Peter Knauth ◽  
Ralf Bohnensack ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Plasma Membrane ◽  
Golgi Apparatus ◽  
Cell Surface ◽  
Mammalian Cells ◽  
Tight Control ◽  
Yeast Two Hybrid ◽  
Sorting Nexin ◽  
Key Steps ◽  
Two Hybrid

The transient appearance of P-selectin on the surface of endothelial cells helps recruit leukocytes into sites of inflammation. The tight control of cell surface P-selectin on these cells depends on regulated exocytosis of Weibel-Palade bodies where the protein is stored and on its rapid endocytosis. After endocytosis, P-selectin is either sorted via endosomes and the Golgi apparatus for storage in Weibel-Palade bodies or targeted to lysosomes for degradation. A potential player in this complex endocytic itinerary is SNX17, a member of the sorting nexin family, which has been shown in a yeast two-hybrid assay to bind P-selectin. Here, we show that overexpression of SNX17 in mammalian cells can influence two key steps in the endocytic trafficking of P-selectin. First, it promotes the endocytosis of P-selectin from the plasma membrane. Second, it inhibits the movement of P-selectin into lysosomes, thereby reducing its degradation.

Mammalian GPI-anchor modifications and the enzymes involved

2020 ◽  
Vol 48 (3) ◽  
pp. 1129-1138 ◽  
Author(s):  
Yi-Shi Liu ◽  
Morihisa Fujita
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Golgi Apparatus ◽  
Cell Surface ◽  
Lipid Rafts ◽  
Mammalian Cells ◽  
Gpi Anchor ◽  
C Terminus ◽  
Lipid Moiety ◽  
Human Proteins

Glycosylphosphatidylinositol (GPI) is a glycolipid added to the C-terminus of a large variety of proteins in eukaryotes, thereby anchoring these proteins to the cell surface. More than 150 different human proteins are modified with GPI, and GPI-anchored proteins (GPI-APs) play critical roles in embryogenesis, neurogenesis, immunity, and fertilization. GPI-APs are biosynthesized in the endoplasmic reticulum (ER) and transported to the plasma membrane via the Golgi apparatus. During transport, GPI-APs undergo structural remodeling that is important for the efficient folding and sorting of GPI-APs. Asparagine-linked glycan-dependent folding and deacylation by PGAP1 work together to ensure that correctly folded GPI-APs are transported from the ER to the Golgi. Remodeling of the GPI lipid moiety is critical for the association of GPI-APs with lipid rafts. On the cell surface, certain GPI-APs are cleaved by GPI cleavage enzymes and released from the membrane, a key event in processes such as spermatogenesis and neurogenesis. In this review, we discuss the enzymes involved in GPI-AP biosynthesis and the fate of GPI-APs in mammalian cells, with a focus on the assembly, folding, degradation, and cleavage of GPI-APs.

scholarly journals The Catenin p120ctnInteracts with Kaiso, a Novel BTB/POZ Domain Zinc Finger Transcription Factor

1999 ◽  
Vol 19 (5) ◽  
pp. 3614-3623 ◽  
Author(s):  
Juliet M. Daniel ◽  
Albert B. Reynolds
Keyword(s):  
Transcription Factor ◽  
Monoclonal Antibodies ◽  
Cell Adhesion ◽  
Mammalian Cells ◽  
Yeast Two Hybrid ◽  
Amino Terminal ◽  
Juxtamembrane Region ◽  
Carboxy Terminal ◽  
Two Hybrid ◽  
E Cadherin

ABSTRACT p120 ctn is an Armadillo repeat domain protein with structural similarity to the cell adhesion cofactors β-catenin and plakoglobin. All three proteins interact directly with the cytoplasmic domain of the transmembrane cell adhesion molecule E-cadherin; β-catenin and plakoglobin bind a carboxy-terminal region in a mutually exclusive manner, while p120 binds the juxtamembrane region. Unlike β-catenin and plakoglobin, p120 does not interact with α-catenin, the tumor suppressor adenomatous polyposis coli (APC), or the transcription factor Lef-1, suggesting that it has unique binding partners and plays a distinct role in the cadherin-catenin complex. Using p120 as bait, we conducted a yeast two-hybrid screen and identified a novel transcription factor which we named Kaiso. Kaiso’s deduced amino acid sequence revealed an amino-terminal BTB/POZ protein-protein interaction domain and three carboxy-terminal zinc fingers of the C2H2 DNA-binding type. Kaiso thus belongs to a rapidly growing family of POZ-ZF transcription factors that include the Drosophila developmental regulators Tramtrak and Bric à brac, and the human oncoproteins BCL-6 and PLZF, which are causally linked to non-Hodgkins’ lymphoma and acute promyelocytic leukemia, respectively. Monoclonal antibodies to Kaiso were generated and used to immunolocalize the protein and confirm the specificity of the p120-Kaiso interaction in mammalian cells. Kaiso specifically coprecipitated with a variety of p120-specific monoclonal antibodies but not with antibodies to α- or β-catenin, E-cadherin, or APC. Like other POZ-ZF proteins, Kaiso localized to the nucleus and was associated with specific nuclear dots. Yeast two-hybrid interaction assays mapped the binding domains to Arm repeats 1 to 7 of p120 and the carboxy-terminal 200 amino acids of Kaiso. In addition, Kaiso homodimerized via its POZ domain but it did not heterodimerize with BCL-6, which heterodimerizes with PLZF. The involvement of POZ-ZF proteins in development and cancer makes Kaiso an interesting candidate for a downstream effector of cadherin and/or p120 signaling.

scholarly journals Caenorhabditis elegans SMG-2 Selectively Marks mRNAs Containing Premature Translation Termination Codons

2007 ◽  
Vol 27 (16) ◽  
pp. 5630-5638 ◽  
Author(s):  
Lisa Johns ◽  
Andrew Grimson ◽  
Sherry L. Kuchma ◽  
Carrie Loushin Newman ◽  
Philip Anderson
Keyword(s):  
Caenorhabditis Elegans ◽  
Mammalian Cells ◽  
Translation Termination ◽  
Yeast Two Hybrid ◽  
Eukaryotic Mrnas ◽  
Nonsense Mediated Mrna Decay ◽  
Endogenous Genes ◽  
Alternatively Spliced ◽  
Two Hybrid ◽  
Premature Translation Termination

ABSTRACT Eukaryotic mRNAs containing premature translation termination codons (PTCs) are rapidly degraded by a process termed “nonsense-mediated mRNA decay” (NMD). We examined protein-protein and protein-RNA interactions among Caenorhabditis elegans proteins required for NMD. SMG-2, SMG-3, and SMG-4 are orthologs of yeast (Saccharomyces cerevisiae) and mammalian Upf1, Upf2, and Upf3, respectively. A combination of immunoprecipitation and yeast two-hybrid experiments indicated that SMG-2 interacts with SMG-3, SMG-3 interacts with SMG-4, and SMG-2 interacts indirectly with SMG-4 via shared interactions with SMG-3. Such interactions are similar to those observed in yeast and mammalian cells. SMG-2-SMG-3-SMG-4 interactions require neither SMG-2 phosphorylation, which is abolished in smg-1 mutants, nor SMG-2 dephosphorylation, which is reduced or eliminated in smg-5 mutants. SMG-2 preferentially associates with PTC-containing mRNAs. We monitored the association of SMG-2, SMG-3, and SMG-4 with mRNAs of five endogenous genes whose mRNAs are alternatively spliced to either contain or not contain PTCs. SMG-2 associates with both PTC-free and PTC-containing mRNPs, but it strongly and preferentially associates with (“marks”) those containing PTCs. SMG-2 marking of PTC-mRNPs is enhanced by SMG-3 and SMG-4, but SMG-3 and SMG-4 are not detectably associated with the same mRNPs. Neither SMG-2 phosphorylation nor dephosphorylation is required for selective association of SMG-2 with PTC-containing mRNPs, indicating that SMG-2 is phosphorylated only after premature terminations have been discriminated from normal terminations. We discuss these observations with regard to the functions of SMG-2 and its phosphorylation during NMD.

scholarly journals Mammalian Homologue of the Caenorhabditis elegans UNC-76 Protein Involved in Axonal Outgrowth Is a Protein Kinase C ζ–interacting Protein

1999 ◽  
Vol 144 (3) ◽  
pp. 403-411 ◽  
Author(s):  
Shun'ichi Kuroda ◽  
Noritaka Nakagawa ◽  
Chiharu Tokunaga ◽  
Kenji Tatematsu ◽  
Katsuyuki Tanizawa
Keyword(s):  
Plasma Membrane ◽  
Protein Kinase C ◽  
Caenorhabditis Elegans ◽  
Protein Kinase ◽  
Rat Brain ◽  
Axonal Outgrowth ◽  
Yeast Two Hybrid ◽  
Interacting Protein ◽  
Kinase C ◽  
Two Hybrid

By the yeast two-hybrid screening of a rat brain cDNA library with the regulatory domain of protein kinase C ζ (PKCζ) as a bait, we have cloned a gene coding for a novel PKCζ-interacting protein homologous to the Caenorhabditis elegans UNC-76 protein involved in axonal outgrowth and fasciculation. The protein designated FEZ1 (fasciculation and elongation protein zeta-1) consisting of 393 amino acid residues shows a high Asp/Glu content and contains several regions predicted to form amphipathic helices. Northern blot analysis has revealed that FEZ1 mRNA is abundantly expressed in adult rat brain and throughout the developmental stages of mouse embryo. By the yeast two-hybrid assay with various deletion mutants of PKC, FEZ1 was shown to interact with the NH2-terminal variable region (V1) of PKCζ and weakly with that of PKCε. In the COS-7 cells coexpressing FEZ1 and PKCζ, FEZ1 was present mainly in the plasma membrane, associating with PKCζ and being phosphorylated. These results indicate that FEZ1 is a novel substrate of PKCζ. When the constitutively active mutant of PKCζ was used, FEZ1 was found in the cytoplasm of COS-7 cells. Upon treatment of the cells with a PKC inhibitor, staurosporin, FEZ1 was translocated from the cytoplasm to the plasma membrane, suggesting that the cytoplasmic translocation of FEZ1 is directly regulated by the PKCζ activity. Although expression of FEZ1 alone had no effect on PC12 cells, coexpression of FEZ1 and constitutively active PKCζ stimulated the neuronal differentiation of PC12 cells. Combined with the recent finding that a human FEZ1 protein is able to complement the function of UNC-76 necessary for normal axonal bundling and elongation within axon bundles in the nematode, these results suggest that FEZ1 plays a crucial role in the axon guidance machinery in mammals by interacting with PKCζ.

scholarly journals Mechanotransduction in an extracted cell model: Fyn drives stretch- and flow-elicited PECAM-1 phosphorylation

2008 ◽  
Vol 182 (4) ◽  
pp. 753-763 ◽  
Author(s):  
Yi-Jen Chiu ◽  
Elena McBeath ◽  
Keigi Fujiwara
Keyword(s):  
Endothelial Cells ◽  
Plasma Membrane ◽  
Adhesion Molecule ◽  
Mammalian Cells ◽  
Kinase Inhibitors ◽  
Vascular Endothelial Cells ◽  
Cell Model ◽  
Vascular Endothelial ◽  
Small Interfering Rnas ◽  
Essential Components

Mechanosensing followed by mechanoresponses by cells is well established, but the mechanisms by which mechanical force is converted into biochemical events are poorly understood. Vascular endothelial cells (ECs) exhibit flow- and stretch-dependent responses and are widely used as a model for studying mechanotransduction in mammalian cells. Platelet EC adhesion molecule 1 (PECAM-1) is tyrosine phosphorylated when ECs are exposed to flow or when PECAM-1 is directly pulled, suggesting that it is a mechanochemical converter. We show that PECAM-1 phosphorylation occurs when detergent-extracted EC monolayers are stretched, indicating that this phosphorylation is mechanically triggered and does not require the intact plasma membrane and soluble cytoplasmic components. Using kinase inhibitors and small interfering RNAs, we identify Fyn as the PECAM-1 kinase associated with the model. We further show that stretch- and flow-induced PECAM-1 phosphorylation in intact ECs is abolished when Fyn expression is down-regulated. We suggest that PECAM-1 and Fyn are essential components of a PECAM-1–based mechanosensory complex in ECs.

scholarly journals Cell surface recycling in yeast: mechanisms and machineries

2016 ◽  
Vol 44 (2) ◽  
pp. 474-478 ◽  
Author(s):  
Chris MacDonald ◽  
Robert C. Piper
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Plasma Membrane ◽  
Membrane Protein ◽  
Cell Surface ◽  
Mammalian Cells ◽  
Genetic System ◽  
Integral Membrane Protein ◽  
Protein Activity ◽  
Yeast Saccharomyces Cerevisiae ◽  
Central Process

Sorting internalized proteins and lipids back to the cell surface controls the supply of molecules throughout the cell and regulates integral membrane protein activity at the surface. One central process in mammalian cells is the transit of cargo from endosomes back to the plasma membrane (PM) directly, along a route that bypasses retrograde movement to the Golgi. Despite recognition of this pathway for decades we are only beginning to understand the machinery controlling this overall process. The budding yeast Saccharomyces cerevisiae, a stalwart genetic system, has been routinely used to identify fundamental proteins and their modes of action in conserved trafficking pathways. However, the study of cell surface recycling from endosomes in yeast is hampered by difficulties that obscure visualization of the pathway. Here we briefly discuss how recycling is likely a more prevalent process in yeast than is widely appreciated and how tools might be built to better study the pathway.

scholarly journals Internalization of Monomeric Lipopolysaccharide Occurs after Transfer Out of Cell Surface Cd14

1999 ◽  
Vol 190 (4) ◽  
pp. 509-522 ◽  
Author(s):  
Thierry Vasselon ◽  
Eric Hailman ◽  
Rolf Thieringer ◽  
Patricia A. Detmers
Keyword(s):  
Plasma Membrane ◽  
Green Fluorescent Protein ◽  
Golgi Apparatus ◽  
Cell Surface ◽  
Enhanced Green Fluorescent Protein ◽  
Fluorescent Protein ◽  
Soluble Cd14 ◽  
Stable Transfectants ◽  
Intracellular Vesicles ◽  
Green Fluorescent

Lipopolysaccharide (LPS) fluorescently labeled with boron dipyrromethane (BODIPY) first binds to the plasma membrane of CD14-expressing cells and is subsequently internalized. Intracellular LPS appears in small vesicles near the cell surface and later in larger, punctate structures identified as the Golgi apparatus. To determine if membrane (m)CD14 directs the movement of LPS to the Golgi apparatus, an mCD14 chimera containing enhanced green fluorescent protein (mCD14–EGFP) was used to follow trafficking of mCD14 and BODIPY–LPS in stable transfectants. The chimera was expressed strongly on the cell surface and also in a Golgi complex–like structure. mCD14–EGFP was functional in mediating binding of and responses to LPS. BODIPY–LPS presented to the transfectants as complexes with soluble CD14 first colocalized with mCD14–EGFP on the cell surface. However, within 5–10 min, the BODIPY–LPS distributed to intracellular vesicles that did not contain mCD14–EGFP, indicating that mCD14 did not accompany LPS during endocytic movement. These results suggest that monomeric LPS is transferred out of mCD14 at the plasma membrane and traffics within the cell independently of mCD14. In contrast, aggregates of LPS were internalized in association with mCD14, suggesting that LPS clearance occurs via a pathway distinct from that which leads to signaling via monomeric LPS.

scholarly journals FLIP Protects against Hypoxia/Reoxygenation-Induced Endothelial Cell Apoptosis by Inhibiting Bax Activation

2005 ◽  
Vol 25 (11) ◽  
pp. 4742-4751 ◽  
Author(s):  
Xue Wang ◽  
Yong Wang ◽  
Jinglan Zhang ◽  
Hong Pyo Kim ◽  
Stefan W. Ryter ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Cell Death ◽  
Plasma Membrane ◽  
Golgi Apparatus ◽  
Death Receptor ◽  
Mouse Lung ◽  
Caspase 8 ◽  
Apoptotic Pathways ◽  
Disc Formation ◽  
Hypoxia Reoxygenation

ABSTRACT Hypoxia/reoxygenation causes cell death, yet the underlying regulatory mechanisms remain partially understood. Recent studies demonstrate that hypoxia/reoxygenation can activate death receptor and mitochondria-dependent apoptotic pathways, involving Bid and Bax mitochondrial translocation and cytochrome c release. Using mouse lung endothelial cells (MLEC), we examined the role of FLIP, an inhibitor of caspase 8, in hypoxia/reoxygenation-induced cell death. FLIP protected MLEC against hypoxia/reoxygenation by blocking both caspase 8/Bid and Bax/mitochondrial apoptotic pathways. FLIP inhibited Bax activation in wild-type and Bid−/− MLEC, indicating independence from the caspase 8/Bid pathway. FLIP also inhibited the expression and activation of protein kinase C (PKC) (α, ζ) during hypoxia/reoxygenation and promoted an association of inactive forms of PKC with Bax. Surprisingly, FLIP expression also inhibited death-inducing signal complex (DISC) formation in the plasma membrane and promoted the accumulation of the DISC in the Golgi apparatus. FLIP expression also upregulated Bcl-XL, an antiapoptotic protein. In conclusion, FLIP decreased DISC formation in the plasma membrane by blocking its translocation from the Golgi apparatus and inhibited Bax activation through a novel PKC-dependent mechanism. The inhibitory effects of FLIP on Bax activation and plasma membrane DISC formation may play significant roles in protecting endothelial cells from the lethal effects of hypoxia/reoxygenation.

Interaction of the synaptic protein PICK1 (protein interacting with C kinase 1) with the non-voltage gated sodium channels BNC1 (brain Na+ channel 1) and ASIC (acid-sensing ion channel)

2002 ◽  
Vol 361 (3) ◽  
pp. 443-450 ◽  
Author(s):  
Alesia M. HRUSKA-HAGEMAN ◽  
John A. WEMMIE ◽  
Margaret P. PRICE ◽  
Michael J. WELSH
Keyword(s):  
Ion Channel ◽  
Mammalian Cells ◽  
Hippocampal Neurons ◽  
Sequence Similarity ◽  
Expression System ◽  
Pdz Domain ◽  
Mammalian Brain ◽  
Na Channel ◽  
Yeast Two Hybrid ◽  
Two Hybrid

Neuronal members of the degenerin/epithelial Na+ channel (DEG/ENaC) family of cation channels include the mammalian brain Na+ channel 1 (BNC1), acid-sensing ion channel (ASIC) and dorsal-root acid-sensing ion channel (DRASIC). Their response to acidic pH, their sequence similarity to nematode proteins involved in mechanotransduction and their modulation by neuropeptides suggest that they may function as receptors for a number of different stimuli. Using the yeast two-hybrid assay, we found that the PDZ domain-containing protein PICK1 (protein interacting with C kinase) interacts specifically with the C-termini of BNC1 and ASIC, but not DRASIC or the related αENaC or βENaC. In both the yeast two-hybrid system and mammalian cells, deletion of the BNC1 and ASIC C-termini abolished the interaction with PICK1. Likewise, mutating the PDZ domain in PICK1 abolished its interaction with BNC1 and ASIC. In addition, in a heterologous expression system PICK1 altered the distribution of BNC1 channels; this effect was dependent on the PDZ domain of PICK1 and the C-terminus of BNC1. We found crude synaptosomal fractions of brain to be enriched in ASIC, suggesting a possible synaptic localization. Moreover, in transfected hippocampal neurons ASIC co-localized with PICK1 in a punctate pattern at synapses. These data suggest that PICK1 binds ASIC and BNC1 via its PDZ domain. This interaction may be important for the localization and/or function of these channels in both the central and peripheral nervous systems.

scholarly journals The Rotavirus Enterotoxin NSP4 Directly Interacts with the Caveolar Structural Protein Caveolin-1

2006 ◽  
Vol 80 (6) ◽  
pp. 2842-2854 ◽  
Author(s):  
Rebecca D. Parr ◽  
Stephen M. Storey ◽  
DeAnne M. Mitchell ◽  
Avery L. McIntosh ◽  
Minglong Zhou ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Laser Scanning ◽  
Nonstructural Protein ◽  
Direct Interaction ◽  
Cell Periphery ◽  
Structural Protein ◽  
Yeast Two Hybrid ◽  
Ussing Chambers ◽  
Caveolin 1 ◽  
Two Hybrid

ABSTRACT Rotavirus nonstructural protein 4 (NSP4) is known to function as an intracellular receptor at the endoplasmic reticulum (ER) critical to viral morphogenesis and is the first characterized viral enterotoxin. Exogenously added NSP4 induces diarrhea in rodent pups and stimulates secretory chloride currents across intestinal segments as measured in Ussing chambers. Circular dichroism studies further reveal that intact NSP4 and the enterotoxic peptide (NSP4114-135) that is located within the extended, C-terminal amphipathic helix preferentially interact with caveola-like model membranes. We now show colocalization of NSP4 and caveolin-1 in NSP4-transfected and rotavirus-infected mammalian cells in reticular structures surrounding the nucleus (likely ER), in the cytosol, and at the cell periphery by laser scanning confocal microscopy. A direct interaction between NSP4 residues 112 to 140 and caveolin-1 was determined by the Pro-Quest yeast two-hybrid system with full-length NSP4 and seven overlapping deletion mutants as bait, caveolin-1 as prey, and vice versa. Coimmunoprecipitation of NSP4-caveolin-1 complexes from rotavirus-infected mammalian cells demonstrated that the interaction occurs during viral infection. Finally, binding of caveolin-1 from mammalian cell lysates to Sepharose-bound, NSP4-specific synthetic peptides confirmed the yeast two-hybrid data and further delineated the binding domain to amino acids 114 to 135. We propose that the association of NSP4 and caveolin-1 contributes to NSP4 intracellular trafficking from the ER to the cell surface and speculate that exogenously added NSP4 stimulates signaling molecules located in caveola microdomains.

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