PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Adaptor Protein Complex beta Subunits”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4Linked to original sources
PubMed2002

Colocalisation of the protein tyrosine phosphatases PTP-SL and PTPBR7 with beta4-adaptin in neuronal cells.

The mouse gene Ptprr encodes the neuronal protein tyrosine phosphatases PTP-SL and PTPBR7. These proteins differ in their N-terminal domains, with PTP-SL being a cytosolic, membrane-associated phosphatase and PTPBR7 a type I transmembrane protein. In this study, we further explored the nature of the PTP-SL-associated vesicles in neuronal cells using a panel of organelle markers and noted a comparable subcellular distribution for PTP-SL and the beta4-adaptin subunit of the AP4 complex. PTP-SL, PTPBR7 and beta4-adaptin are localised at the Golgi apparatus and at vesicles throughout the cytoplasm. Immunohistochemical analysis demonstrated that PTP-SL, PTPBR7 and beta4-adaptin are all endogenously expressed in brain. Interestingly, coexpression of PTP-SL and beta4-adaptin leads to an altered subcellular localisation for PTP-SL. Instead of the Golgi and vesicle-type staining pattern, still observable for beta4-adaptin, PTP-SL is now distributed throughout the cytoplasm. Although beta4-adaptin was found to interact with the phosphatase domain of PTP-SL and PTPBR7 in the yeast two-hybrid system, it failed to do so in transfected neuronal cells. Our data suggest that the tyrosine phosphatases PTP-SL and PTPBR7 may be involved in the formation and transport of AP4-coated vesicles or in the dephosphorylation of their transmembrane cargo molecules at or near the Golgi apparatus.

Adaptor Protein Complex beta Subunits↗
PubMed2006

Innate immunity defects in Hermansky-Pudlak type 2 syndrome.

Adaptor protein-3 (AP-3) is an ubiquitous cytoplasmic complex that shuttles cargo proteins from the trans-Golgi and a tubular-endosomal compartment to endosome-lysosome-related organelles. Lack of the beta3A subunit of this complex causes Hermansky-Pudlak syndrome type 2, an autosomal recessive disease characterized by partial albinism, prolonged bleeding tendency, and immunodeficiency. To investigate the pathogenesis of immunodeficiency, we studied natural killer (NK) cells and neutrophil functions in 2 previously unreported siblings affected by Hermansky-Pudlak type 2 syndrome. In both patients we observed a dramatic reduction of cytolytic activity of freshly isolated and of IL-2-activated NK cells. Levels of perforin were reduced in unstimulated NK cells, thereby accounting for the impairment of NK cytolitic activity. In addition, analysis of neutrophils in these patients demonstrated that intracellular elastase content was largely reduced while CD63 expression on plasma membrane was substantially increased. Taken together, these observations suggest that type 2 Hermansky-Pudlak syndrome is characterized by defects of innate immunity.

Adaptor Protein Complex 3↗
PubMed2002

Differential roles of arrestin-2 interaction with clathrin and adaptor protein 2 in G protein-coupled receptor trafficking.

The non-visual arrestins, arrestin-2 and arrestin-3, play a critical role in regulating the signaling and trafficking of many G protein-coupled receptors (GPCRs). Molecular insight into the role of arrestins in GPCR trafficking has suggested that arrestin interaction with clathrin, beta(2)-adaptin (the beta-subunit of the adaptor protein AP2), and phosphoinositides contributes to this process. In the present study, we have attempted to better define the molecular basis and functional role of arrestin-2 interaction with clathrin and beta(2)-adaptin. Site-directed mutagenesis revealed that the C-terminal region of arrestin-2 mediated beta(2)-adaptin and clathrin interaction with Phe-391 and Arg-395 having an essential role in beta(2)-adaptin binding and LIELD (residues 376-380) having an essential role in clathrin binding. Interestingly, arrestin-2-R169E, an activated form of arrestin that binds to GPCRs in a phosphorylation-independent manner, has significantly enhanced binding to beta(2)-adaptin and clathrin. This suggests that receptor-induced conformational changes in the C-terminal tail of arrestin-2 will likely play a major role in mediating arrestin interaction with clathrin-coated pits. In an effort to clarify the role of these interactions in GPCR trafficking we generated arrestin mutants that were completely and selectively defective in either clathrin (arrestin-2-DeltaLIELD) or beta(2)-adaptin (arrestin-2-F391A) interaction. Analysis of these mutants in COS-1 cells revealed that arrestin/clathrin interaction was essential for agonist-promoted internalization of the beta(2)-adrenergic receptor, while arrestin/beta(2)-adaptin interaction appeared less critical. Arrestin-2 mutants defective in both clathrin and beta(2)-adaptin binding functioned as effective dominant negatives in HEK293 cells and significantly attenuated beta(2)-adrenergic receptor internalization. These mutants should prove useful in better defining the role of arrestins in mediating receptor trafficking.

Adaptor Protein Complex beta Subunits↗
PubMed1996

Structure of the promoter and genomic organization of the human beta'-adaptin gene (BAM22) from chromosome 22q12.

Adaptins are major structural components of heterotetrameric protein complexes called adaptors, which are essential in intracellular receptor transport via clathrin-coated vesicles. beta-adaptins constitute one of three known classes (alpha, beta, gamma) of adaptins, including beta and beta' subtypes. We previously cloned the human beta'-adaptin gene (BAM22) (GDB symbol, ADTB1) from chromosome 22q12 and proposed its involvement in the development of meningiomas. Here we describe the genomic organization of this gene, which consists of 22 exons spanning over approximately 100 kb. We also report results from point mutation screening of 7 randomly chosen exons analyzed in 110 sporadic meningiomas. As part of the genomic characterization of the BAM22 locus, we sequenced 40 kb covering exons 1-4 and 12 kb upstream from the start of gene transcription. Analysis of the sequence suggests that the BAM22 gene has a CG-rich promoter.

Adaptor Protein Complex 1↗
PubMed1995

Beta-NAP, a cerebellar degeneration antigen, is a neuron-specific vesicle coat protein.

We have identified a target antigen in autoimmune cerebellar degeneration, beta-NAP, that is closely related to the beta-adaptin and beta-COP coat proteins. Beta-NAP is a nonclathrin-associated phosphoprotein expressed exclusively in neurons, from E12 through adulthood. Beta-NAP is present in the neuronal soma and nerve terminal as soluble and membrane-bound pools and is associated with a discrete set of nerve-terminal vesicles. These results establish beta-NAP as a neuron-specific vesicle coat protein. We propose a model in which beta-NAP mediates vesicle transport between the soma and the axon terminus and suggest that beta-NAP may represent a general class of coat proteins that mediates apical transport in polarized cells.

Adaptor Protein Complex 3↗
PubMed2006

Beta-adaptin: key molecule for microglial scavenger receptor function under oxidative stress.

Scavenger receptors internalize chemically modified low density lipoprotein particles (ac-LDL) and other ligands through the process of receptor-mediated endocytosis. During this investigation using amyloid-beta as a natural ligand for the SR, we studied under a ligand-induced oxidative stress condition, changes in protein expression of several adaptor proteins important in the organization of the endocytic machinery in microglia and macrophages. Differential expression experiments of beta-adaptin, alpha-adaptin, SR-AI, and SR-BI in RAW (macrophages) and EOC (microglia) cells were performed according to dosage and exposure time to amyloid-beta. Our results show that according to dosage, amyloid-beta produces an oxidative stress state that importantly affects the availability of beta-adaptin. Under these conditions, RT-PCR assays show that beta-adaptin mRNA is normally synthesized, reason why protein translation or protein structure of beta-adaptin might be altered. These observations might have impact in the understanding of the mechanisms microglia employ to process amyloid-beta in the brain.

Adaptor Protein Complex beta Subunits↗
PubMed2004

Leishmania major: clathrin and adaptin complexes of an intra-cellular parasite.

To investigate the role of clathrin-mediated trafficking during the Leishmania lifecycle, open reading frames encoding clathrin heavy chain and the beta-adaptins, major components of the adaptor complexes, have been analysed both in silico and experimentally. The Leishmania genome encodes three beta-adaptins, which arose at a time predating speciation of these divergent trypanosomatids. Unlike Trypanosoma brucei, both clathrin heavy chain and beta-adaptin1 are constitutively expressed throughout the Leishmania life cycle. Clathrin relocalises in amastigotes relative to promastigotes, consistent with developmental alterations to the morphology of the endo-membrane system.

Adaptor Protein Complex beta Subunits↗
PubMed1999

Hippocampal auditory gating in the hyperactive mocha mouse.

The mouse mutants mocha (mh) and mocha2J (mh2J) result from separate mutations in the same gene (AP-3 delta) that arose independently on different backgrounds of inbred strains. They exhibit a neurological phenotype that includes hyperactivity, an epileptiform EEG and changes in the basic function of the hippocampus. Depth electrode recordings of hippocampal auditory evoked potentials revealed that the response to the first of two paired tones was significantly enhanced in mocha and mocha2J, as compared with littermate controls. The pronounced theta rhythm characteristic of unanesthetized mocha mice was not observed in these chloral-hydrate anesthetized mice, whereas spike discharge activity was frequently present in the recordings.

Acoustic Stimulation↗
PubMed2002

Using new genetic tools to study the pathogenesis of Blastomyces dermatitidis.

Fungal pathogens have emerged as a public health menace owing to the expanding population of vulnerable patients and a heightened exposure to fungi in our environment, particularly for the systemic dimorphic fungi that inhabit soil worldwide. A better understanding of these invaders and their pathogenic mechanisms is badly needed to further research into therapeutic options. Advances in the molecular tools available for genetic manipulation of Blastomyces dermatitidis have enhanced our ability to study this poorly understood dimorphic fungal pathogen. Recent refinements in gene-transfer techniques, new selection markers, reliable reporter fusions and successes in gene targeting have shed light upon the importance of the mycelium-to-yeast transition and the crucial and complex role the BAD1 adhesin plays in pathogenesis.

Adaptor Protein Complex beta Subunits↗
PubMed2003

Glycine binding primes NMDA receptor internalization.

NMDA (N-methyl-d-aspartate) receptors (NMDARs) are a principal subtype of excitatory ligand-gated ion channel with prominent roles in physiological and disease processes in the central nervous system. Recognition that glycine potentiates NMDAR-mediated currents as well as being a requisite co-agonist of the NMDAR subtype of 'glutamate' receptor profoundly changed our understanding of chemical synaptic communication in the central nervous system. The binding of both glycine and glutamate is necessary to cause opening of the NMDAR conductance pore. Although binding of either agonist alone is insufficient to cause current flow through the channel, we report here that stimulation of the glycine site initiates signalling through the NMDAR complex, priming the receptors for clathrin-dependent endocytosis. Glycine binding alone does not cause the receptor to be endocytosed; this requires both glycine and glutamate site activation of NMDARs. The priming effect of glycine is mimicked by the NMDAR glycine site agonist d-serine, and is blocked by competitive glycine site antagonists. Synaptic as well as extrasynaptic NMDARs are primed for internalization by glycine site stimulation. Our results demonstrate transmembrane signal transduction through activating the glycine site of NMDARs, and elucidate a model for modulating cell-cell communication in the central nervous system.

Adaptor Protein Complex beta Subunits↗
PubMed2003

Adaptor protein 3-dependent microtubule-mediated movement of lytic granules to the immunological synapse.

Hermansky-Pudlak syndrome (HPS) is a rare autosomal recessive disease characterized by platelet defects and oculocutaneous albinism. Individuals with HPS type 2 (HPS2) lack the cytosolic adaptor protein 3 (AP-3) involved in lysosomal sorting, and are also immunodeficient. Here we characterize an HPS2 mutation and demonstrate that AP-3 deficiency leads to a loss of cytotoxic T lymphocyte (CTL)-mediated cytotoxicity. Although the lysosomal protein CD63 was mislocalized to the plasma membrane, perforin and granzymes were correctly localized to the lytic granules in AP-3-deficient CTLs. However, the lytic granules of AP-3-deficient CTLs were enlarged and were unable to move along microtubules and dock within the secretory domain of the immunological synapse. These data show that AP-3 is essential for polarized secretion from CTLs.

Adaptor Protein Complex 3↗
PubMed1998

ATM binds to beta-adaptin in cytoplasmic vesicles.

Inherited mutations in the ATM gene lead to a complex clinical phenotype characterized by neuronal degeneration, oculocutaneous telangiectasias, immune dysfunction, and cancer predisposition. Using the yeast two-hybrid system, we demonstrate that ataxia telangiectasia mutated (ATM) binds to beta-adaptin, one of the components of the AP-2 adaptor complex, which is involved in clathrin-mediated endocytosis of receptors. The interaction between ATM and beta-adaptin was confirmed in vitro, and coimmunoprecipitation and colocalization studies show that the proteins also associate in vivo. ATM also interacts in vitro with beta-NAP, a neuronal-specific beta-adaptin homolog that was identified as an autoantigen in a patient with cerebellar degeneration. Our data describing the association of ATM with beta-adaptin in vesicles indicate that ATM may play a role in intracellular vesicle and/or protein transport mechanisms.

Adaptor Protein Complex 3↗
PubMed2002

Neuronal leucine-rich repeat protein-3 amplifies MAPK activation by epidermal growth factor through a carboxyl-terminal region containing endocytosis motifs.

Neuronal leucine-rich repeat protein-3 (NLRR-3) belongs to the LRR superfamily. Expression of rat NLRR-3 gene isolated from c-Ha-ras transgenic rat tumor is regulated mainly through the Ras-MAPK signaling pathway. NLRR-3 was found to enhance phosphorylation of MAPK when COS-7 cells were transfected with NLRR-3 and stimulated with a low concentration (0.01 ng/ml) of epidermal growth factor (EGF), but the amplification of MAPK phosphorylation by NLRR-3 was no longer observed when the carboxyl-terminal 30 amino acid stretch containing clathrin-mediated endocytosis motifs was deleted. A green fluorescent protein-tagged NLRR-3 localized at the plasma membrane was efficiently internalized in COS-7 cells, but internalization of a carboxyl-terminal-deleted version (NLRRDeltaC) was less efficient. The presence of clathrin-adaptor protein complexes containing NLRR-3 in brain lysate was confirmed by immunoprecipitation and glutathione S-transferase pull-down experiments, and affinity column chromatography revealed that the carboxyl-terminal region of NLRR-3 interacts with beta-adaptin. We propose that NLRR-3 potentiates Ras-MAPK signaling by facilitating internalization of EGF in clathrin-coated vesicles.

3T3 Cells↗
PubMed2002

Regulation of arrestin-3 phosphorylation by casein kinase II.

Arrestins play an important role in regulating the function of G protein-coupled receptors including receptor desensitization, internalization, down-regulation, and signaling via nonreceptor tyrosine kinases and mitogen-activated protein kinases. Previous studies have revealed that arrestins themselves are also subject to regulation. In the present study, we focused on identifying potential mechanisms involved in regulating the function of arrestin-3. Using metabolic labeling, phosphoamino acid analysis, and mutagenesis studies, we found that arrestin-3 is constitutively phosphorylated at Thr-382 and becomes dephosphorylated upon beta(2)-adrenergic receptor activation in COS-1 cells. Casein kinase II (CKII) appears to be the major kinase mediating arrestin-3 phosphorylation, since 1) Thr-382 is contained within a canonical consensus sequence for CKII phosphorylation and 2) wild type arrestin-3 but not a T382A mutant is phosphorylated by CKII in vitro. Functional analysis reveals that mutants mimicking the phosphorylated (T382E) and dephosphorylated (T382A or T382V) states of arrestin-3 promote beta(2)-adrenergic receptor internalization and bind clathrin, beta-adaptin, and Src to comparable levels as wild type arrestin-3. This suggests that the phosphorylation of arrestin-3 does not directly regulate interaction with endocytic (clathrin, beta-adaptin) or signaling (Src) components and is in contrast to arrestin-2, where phosphorylation appears to regulate interaction with clathrin and Src. However, additional analysis reveals that arrestin-3 phosphorylation may regulate formation of a large arrestin-3-containing protein complex. Differences between the regulatory roles of arrestin-2 and -3 phosphorylation may contribute to the different cellular functions of these proteins in G protein-coupled receptor signaling and regulation.

Adaptor Protein Complex beta Subunits↗
PubMed1996

Transferrin receptor containing the SDYQRL motif of TGN38 causes a reorganization of the recycling compartment but is not targeted to the TGN.

The SDYQRL motif of the cytoplasmic domain of TGN38 is involved in targeting TGN38 from endosomes to the TGN. To create a system for studying this pathway, we replaced the native transferrin receptor (TR) internalization motif (YTRF) with the SDYQRL TGN-targeting motif. The advantages of using TR as a reporter molecule include the ability to monitor trafficking, in both biochemical and microscopy experiments, using the natural ligand transferrin. When expressed in CHO cells, the SDYQRL-TR construct accumulated in juxtanuclear tubules and vesicles that are in the vicinity of the TGN. The SDYQRL-TR-containing structures, however, do not colocalize with TGN markers (e.g., NBD ceramide), and therefore the SDYQRL motif is not sufficient to target the TR to the TGN. The morphology of the SDYQRL-TR-containing juxtanuclear structures is different from the recycling compartment found in cells expressing the wild-type TR. In addition, the SDYQRL-TR-containing juxtanuclear compartment is more acidic than the recycling compartment in cells expressing the wild-type TR. The juxtanuclear compartment, however, is a bona fide recycling compartment since SDYQRL-TR was recycled back to the cell surface at a rate comparable to the wild-type TR, and sphingomyelin and cellubrevin, both of which label all compartments of the endocytic recycling pathway, colocalize with SDYQRL-TR in the juxtanuclear structures. These findings demonstrate that expression of the SDYQRL-TR construct alters the morphology and pH of endocytic recycling compartments rather than selectively affecting the intracellular trafficking pathway of the SDYQRL-TR construct. Therefore, the SDYQRL trafficking motif is not simply a molecular address that targets proteins to the TGN, but it can play an active role in determining the physical characteristics of endosomal compartments.

Acids↗
PubMed2003

Cophosphorylation of amphiphysin I and dynamin I by Cdk5 regulates clathrin-mediated endocytosis of synaptic vesicles.

It has been thought that clathrin-mediated endocytosis is regulated by phosphorylation and dephosphorylation of many endocytic proteins, including amphiphysin I and dynamin I. Here, we show that Cdk5/p35-dependent cophosphorylation of amphiphysin I and dynamin I plays a critical role in such processes. Cdk5 inhibitors enhanced the electric stimulation-induced endocytosis in hippocampal neurons, and the endocytosis was also enhanced in the neurons of p35-deficient mice. Cdk5 phosphorylated the proline-rich domain of both amphiphysin I and dynamin I in vitro and in vivo. Cdk5-dependent phosphorylation of amphiphysin I inhibited the association with beta-adaptin. Furthermore, the phosphorylation of dynamin I blocked its binding to amphiphysin I. The phosphorylation of each protein reduced the copolymerization into a ring formation in a cell-free system. Moreover, the phosphorylation of both proteins completely disrupted the copolymerization into a ring formation. Finally, phosphorylation of both proteins was undetectable in p35-deficient mice.

Adaptor Protein Complex beta Subunits↗