Subunit H of the V-ATPase Involved in Endocytosis Shows Homology to β-Adaptins

The vacuolar ATPase (V-ATPase) is a multisubunit enzyme that facilitates the acidification of intracellular compartments in eukaryotic cells and plays an important role in receptor-mediated endocytosis, intracellular trafficking processes, and protein degradation. In this study we show that the C-terminal fragment of 350 residues of the regulatory subunit H (V1H) of the V-ATPase shares structural and functional homologies with the β-chains of adaptor protein complexes. Moreover, the fragment is similar to a region in the β-subunit of COPI coatomer complexes, which suggests the existence of a shared domain in these three different families of proteins. For β-adaptins, this fragment binds to cytoplasmic di-leucine–based sorting motifs such as in HIV-1 Nef that mediate endocytic trafficking. Expression of this fragment in cells blocks the internalization of transmembrane proteins, which depend on di-leucine–based motifs, whereas mutation of the consensus sequence GEY only partly diminishes the recognition of the sorting motif. Based on recent structural analysis, our results suggest that the di-leucine-binding domain consists of a HEAT or ARM repeat protein fold.

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Interactions of HIV-1 Nef with the μ Subunits of Adaptor Protein Complexes 1, 2, and 3: Role of the Dileucine-Based Sorting Motif

Virology ◽

10.1006/viro.2000.0277 ◽

2000 ◽

Vol 271 (1) ◽

pp. 9-17 ◽

Cited By ~ 76

Author(s):

Heather M. Craig ◽

Thipparthi R. Reddy ◽

Nanette L. Riggs ◽

Philip P. Dao ◽

John C. Guatelli

Keyword(s):

Protein Complexes ◽

Adaptor Protein ◽

Sorting Motif ◽

Hiv 1

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Phosphoserine acidic cluster motifs in the cytoplasmic domains of transmembrane proteins bind distinct basic regions on the μ subunits of clathrin adaptor protein complexes

10.1101/286633 ◽

2018 ◽

Author(s):

Rajendra Singh ◽

Charlotte Stoneham ◽

Christopher Lim ◽

Xiaofei Jia ◽

Javier Guenaga ◽

...

Keyword(s):

Protein Trafficking ◽

Transmembrane Proteins ◽

Adaptor Protein ◽

Cellular Protein ◽

Membrane Lipid ◽

Dependent Manner ◽

Cytoplasmic Domains ◽

Clathrin Adaptor ◽

Hiv 1

AbstractProtein trafficking in the endosomal system involves the recognition of specific signals within the cytoplasmic domains (CDs) of transmembrane proteins by clathrin adaptors. One such signal is the phosphoserine acidic cluster (PSAC), the prototype of which is in the endoprotease Furin. How PSACs are recognized by clathrin adaptors has been controversial. We reported previously that HIV-1 Vpu, which modulates cellular immunoreceptors, contains a PSAC that binds to the µ subunits of clathrin adaptor protein (AP) complexes. Here, we show that the CD of Furin binds the µ subunits of AP-1 and AP-2 in a phosphorylation-dependent manner. Moreover, we identify a PSAC in a cytoplasmic loop of the cellular transmembrane Serinc3, an inhibitor of the infectivity of retroviruses. The two serines within the PSAC of Serinc3 are phosphorylated by casein kinase II and mediate interaction with the µ subunits in vitro. The sites of these serines vary among mammals in a manner consistent with host-pathogen conflict, yet the Serinc3-PSAC seems dispensible for anti-HIV activity and for counteraction by HIV-1 Nef. The CDs of Vpu, Furin, and the PSAC-containing loop of Serinc3 each bind the μ subunit of AP-2 (µ2) with similar affinities, but they appear to utilize different basic regions on µ2. The Serinc3 loop requires a region previously reported to bind the acidic plasma membrane lipid phosphatidylinositol-4,5-bisphosphate. These data suggest that the PSACs within different proteins recognize different basic regions on the µ surface, providing the potential to inhibit the activity of viral proteins without necessarily affecting cellular protein trafficking.

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S-Palmitoylation determines TMEM55B-dependent positioning of lysosomes

Journal of Cell Science ◽

10.1242/jcs.258566 ◽

2021 ◽

Author(s):

Sönke Rudnik ◽

Saskia Heybrock ◽

Paul Saftig ◽

Markus Damme

Keyword(s):

Molecular Motors ◽

Protein Complexes ◽

Critical Role ◽

Adaptor Protein ◽

Retrograde Transport ◽

Microtubule Motors ◽

Lysosomal Sorting ◽

Sorting Motif ◽

Spatio Temporal

The spatio-temporal cellular distribution of lysosomes depends on active transport mainly driven by microtubule-motors such as kinesins and dynein. Different protein complexes attach these molecular motors to their vesicular cargo: TMEM55B, as an integral lysosomal membrane protein, is a component of such a complex mediating the retrograde transport of lysosomes by establishing an interaction with the cytosolic scaffold protein JIP4 and dynein/dynactin. Here we show that TMEM55B and its paralog TMEM55A are S-palmitoylated proteins and lipidated at multiple cysteine-residues. Mutation of all cysteines in TMEM55B prevents S-palmitoylation and causes the retention of the mutated protein in the Golgi-apparatus. Consequently, non-palmitoylated TMEM55B is no longer able to modulate lysosomal positioning and the perinuclear clustering of lysosomes. Additional mutagenesis of the dileucine-based lysosomal sorting motif in non-palmitoylated TMEM55B leads to partial missorting to the plasma membrane instead of retention in the Golgi, implicating a direct effect of S-palmitoylation on the adaptor-protein-dependent sorting of TMEM55B. Our data suggest a critical role of S-palmitoylation on the trafficking of TMEM55B and TMEM55B-dependent lysosomal positioning.

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The Adaptor Protein Complex 1 limits E-cadherin endocytosis during epithelial morphogenesis

10.1101/2020.10.14.340372 ◽

2020 ◽

Author(s):

Miguel Ramírez Moreno ◽

Katy Boswell ◽

Natalia A. Bulgakova

Keyword(s):

Cell Death ◽

Intracellular Trafficking ◽

Apical Cell ◽

Transmembrane Proteins ◽

Adaptor Protein ◽

Epithelial Morphogenesis ◽

Compensatory Mechanism ◽

Epithelial Polarity ◽

Trafficking Defects ◽

E Cadherin

AbstractIntracellular trafficking regulates the distribution of transmembrane proteins including the key determinants of epithelial polarity and adhesion. The Adaptor Protein 1 (AP-1) complex is the key regulator of vesicle sorting, which binds a large number of specific cargos. We examined roles of the AP-1 complex in epithelial morphogenesis, using the Drosophila wing as a paradigm. We found that AP-1 knockdown leads to ectopic folds caused by trafficking defects of integrins. This occurs concurrently with an increase in the apical cell area and induction of cell death due to defects in E-cadherin trafficking. We discovered a distinct pool of AP-1 localizes at the apical Adherens Junctions, where it limits internalization of E-cadherin from the cell surface. Upon AP-1 knockdown, the accompanying hyperinternalization of E-cadherin induces cell death by an uncharacterised mechanism with a potential tumour-suppressive role. Simultaneously, cells increase expression of E-cadherin in a compensatory mechanism to maintain cell-cell adhesion.

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HIV-1 Nef Stabilizes the Association of Adaptor Protein Complexes with Membranes

Journal of Biological Chemistry ◽

10.1074/jbc.m210115200 ◽

2002 ◽

Vol 278 (10) ◽

pp. 8725-8732 ◽

Cited By ~ 50

Author(s):

Katy Janvier ◽

Heather Craig ◽

Douglas Hitchin ◽

Ricardo Madrid ◽

Nathalie Sol-Foulon ◽

...

Keyword(s):

Protein Complexes ◽

Adaptor Protein ◽

Hiv 1

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Structural basis of HIV-1 Vpu-mediated BST2 antagonism via hijacking of the clathrin adaptor protein complex 1

eLife ◽

10.7554/elife.02362 ◽

2014 ◽

Vol 3 ◽

Cited By ~ 64

Author(s):

Xiaofei Jia ◽

Erin Weber ◽

Andrey Tokarev ◽

Mary Lewinski ◽

Maryan Rizk ◽

...

Keyword(s):

Cell Surface ◽

Membrane Trafficking ◽

Protein Complex ◽

Adaptor Protein ◽

Structural Basis ◽

Host Proteins ◽

Viral Protein U ◽

Sorting Motif ◽

Clathrin Adaptor ◽

Hiv 1

BST2/tetherin, an antiviral restriction factor, inhibits the release of enveloped viruses from the cell surface. Human immunodeficiency virus-1 (HIV-1) antagonizes BST2 through viral protein u (Vpu), which downregulates BST2 from the cell surface. We report the crystal structure of a protein complex containing Vpu and BST2 cytoplasmic domains and the core of the clathrin adaptor protein complex 1 (AP1). This, together with our biochemical and functional validations, reveals how Vpu hijacks the AP1-dependent membrane trafficking pathways to mistraffick BST2. Vpu mimics a canonical acidic dileucine-sorting motif to bind AP1 in the cytosol, while simultaneously interacting with BST2 in the membrane. These interactions enable Vpu to build on an intrinsic interaction between BST2 and AP1, presumably causing the observed retention of BST2 in juxtanuclear endosomes and stimulating its degradation in lysosomes. The ability of Vpu to hijack AP-dependent trafficking pathways suggests a potential common theme for Vpu-mediated downregulation of host proteins.

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Recognition of dileucine-based sorting signals from HIV-1 Nef and LIMP-II by the AP-1 γ–σ1 and AP-3 δ–σ3 hemicomplexes

The Journal of Cell Biology ◽

10.1083/jcb.200307157 ◽

2003 ◽

Vol 163 (6) ◽

pp. 1281-1290 ◽

Cited By ~ 165

Author(s):

Katy Janvier ◽

Yukio Kato ◽

Markus Boehm ◽

Jeremy R. Rose ◽

José A. Martina ◽

...

Keyword(s):

Transmembrane Proteins ◽

Adaptor Protein ◽

Integral Membrane Protein ◽

Negative Factor ◽

Sorting Signals ◽

Immunodeficiency Virus ◽

Sequence Requirements ◽

Hiv 1

The sorting of transmembrane proteins to endosomes and lysosomes is mediated by signals present in the cytosolic tails of the proteins. A subset of these signals conform to the [DE]XXXL[LI] consensus motif and mediate sorting via interactions with heterotetrameric adaptor protein (AP) complexes. However, the identity of the AP subunits that recognize these signals remains controversial. We have used a yeast three-hybrid assay to demonstrate that [DE]XXXL[LI]-type signals from the human immunodeficiency virus negative factor protein and the lysosomal integral membrane protein II interact with combinations of the γ and σ1 subunits of AP-1 and the δ and σ3 subunits of AP-3, but not the analogous combinations of AP-2 and AP-4 subunits. The sequence requirements for these interactions are similar to those for binding to the whole AP complexes in vitro and for function of the signals in vivo. These observations reveal a novel mode of recognition of sorting signals involving the γ/δ and σ subunits of AP-1 and AP-3.

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Adaptor protein complexes and intracellular transport

Bioscience Reports ◽

10.1042/bsr20140069 ◽

2014 ◽

Vol 34 (4) ◽

Cited By ~ 64

Author(s):

Sang Yoon Park ◽

Xiaoli Guo

Keyword(s):

Membrane Trafficking ◽

Intracellular Transport ◽

Protein Complexes ◽

Adaptor Protein ◽

Inherited Disorders ◽

Transport Pathways ◽

Vesicular Carriers ◽

Cargo Proteins ◽

Intracellular Compartments ◽

Secretory Transport

The AP (adaptor protein) complexes are heterotetrameric protein complexes that mediate intracellular membrane trafficking along endocytic and secretory transport pathways. There are five different AP complexes: AP-1, AP-2 and AP-3 are clathrin-associated complexes; whereas AP-4 and AP-5 are not. These five AP complexes localize to different intracellular compartments and mediate membrane trafficking in distinct pathways. They recognize and concentrate cargo proteins into vesicular carriers that mediate transport from a donor membrane to a target organellar membrane. AP complexes play important roles in maintaining the normal physiological function of eukaryotic cells. Dysfunction of AP complexes has been implicated in a variety of inherited disorders, including: MEDNIK (mental retardation, enteropathy, deafness, peripheral neuropathy, ichthyosis and keratodermia) syndrome, Fried syndrome, HPS (Hermansky–Pudlak syndrome) and HSP (hereditary spastic paraplegia).

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