Cloning of Drosophila beta-adaptin and its localization on expression in mammalian cells

1994 ◽  
Vol 107 (3) ◽  
pp. 709-718
Author(s):  
D.R. Camidge ◽  
B.M. Pearse
Keyword(s):  
Plasma Membrane ◽  
Mammalian Cells ◽  
Beta Subunits ◽  
Specific Interactions ◽  
Coated Pits ◽  
Cos Cells ◽  
Amino Terminal ◽  
Differential Interaction ◽  
Expression In Mammalian Cells ◽  
Choice Of Partner

A Drosophila cDNA (BAD1) encoding a structural and assembly-competent homologue of the mammalian coated pit beta-adaptins (beta and beta') has been cloned and sequenced. In its amino-terminal region (residues 1–575), the BAD1 sequence appears intermediate between that of the mammalian beta-adaptin and a predicted sequence, from cDNA 105a, which appears to code for a version of beta'-adaptin. To test its functional characteristics, a ‘myc’-tagged version of BAD1 was expressed in Cos cells. The BAD1 protein was detected most clearly in plasma membrane coated pits, where it colocalized with alpha-adaptin, although other coated pits were noted which apparently did not contain alpha-adaptin. However, these are probably gamma-adaptin containing pits, as BAD1 was also found colocalized with gamma-adaptin in Golgi coated pits in which, typically, alpha-adaptin is absent. Immunoprecipitation experiments confirmed that the BAD1 protein was present in both types of adaptor complex, unlike beta-adaptin which complexes with alpha-adaptin and beta'-adaptin which partners gamma-adaptin exclusively. In spite of this, BAD1 expression does not appear to mix alpha-adaptin and gamma-adaptin distribution amongst all the coated pits: thus the location of these adaptor complexes in mammalian cells does not depend on the differences between beta subunits but rather on membrane-specific interactions of other adaptor polypeptides. The differential interaction of beta with alpha-adaptin and beta' with gamma-adaptin in mammalian cells is likely to depend on the few non-conservative differences between their respective sequences and BAD1. Four of these (one with respect to beta and three versus 105a) are clustered in a particular region (residues 155 to 305), which may therefore represent a domain that influences the choice of partner adaptin.

Endosomal system of Paramecium: coated pits to early endosomes

1992 ◽  
Vol 101 (2) ◽  
pp. 449-461 ◽  
Author(s):  
R.D. Allen ◽  
C.C. Schroeder ◽  
A.K. Fok
Keyword(s):  
Plasma Membrane ◽  
Mammalian Cells ◽  
Fluid Phase ◽  
Early Endosome ◽  
Coated Vesicles ◽  
Striking Similarity ◽  
Coated Pits ◽  
Early Endosomes ◽  
Membrane Components ◽  
Endosomal System

A detailed morphological and tracer study of endocytosis via coated pits in Paramecium multimicronucleatum was undertaken to compare endocytic processes in a free-living protozoon with similar processes in higher organisms. Permanent pits at the cell surface enlarge, become coated and give rise to coated vesicles (188 +/− 41 nm in diameter) that enclose fluid-phase markers such as horseradish peroxidase (HRP). Both the pits and vesicles are labeled by the immunogold technique when a monoclonal antibody (mAb) raised against the plasma membrane of this cell is applied to cryosections. The HRP is delivered to an early endosome compartment, which also shares the plasma membrane antigen. The early endosome, as shown in quick-freeze deep-etch replicas of chemically unfixed cells, is a definitive non-reticular compartment composed of many individual flattened cisternal units of 0.2 to 0.7 microns diameter, each potentially bearing one or more approximately 80-nm-wide coated evaginations. These coated evaginations on the early endosomes contain HRP but are not labeled by the mAb. The coated evaginations pinch off to form a second group of coated vesicles (90 +/− 17 nm in diameter), which can be differentiated from those formed from coated pits by their smaller size, absence of plasma membrane antigen and their location somewhat deeper into the cytoplasm. This study shows a striking similarity between protozoons and mammalian cells in their overall early endosomal machinery and in the ability of early endosomes to sort cargo from plasma membrane components. The vesicles identified in this study form two distinct populations of putative shuttle vesicles, pre-endosomal (large) and early endosome-derived vesicles (small), which facilitate incoming and outgoing traffic from the early endosomes.

The delivery of endocytosed cargo to lysosomes

2009 ◽  
Vol 37 (5) ◽  
pp. 1019-1021 ◽  
Author(s):  
J. Paul Luzio ◽  
Michael D.J. Parkinson ◽  
Sally R. Gray ◽  
Nicholas A. Bright
Keyword(s):  
Plasma Membrane ◽  
Mammalian Cells ◽  
Late Endosome ◽  
Snare Complex ◽  
Coated Pits ◽  
Free System ◽  
Endosomal Sorting ◽  
Protein Receptor ◽  
Late Endosomes ◽  
Early Endosomes

In mammalian cells, endocytosed cargo that is internalized through clathrin-coated pits/vesicles passes through early endosomes and then to late endosomes, before delivery to lysosomes for degradation by proteases. Late endosomes are MVBs (multivesicular bodies) with ubiquitinated membrane proteins destined for lysosomal degradation being sorted into their luminal vesicles by the ESCRT (endosomal sorting complex required for transport) machinery. Cargo is delivered from late endosomes to lysosomes by kissing and direct fusion. These processes have been studied in live cell experiments and a cell-free system. Late endosome–lysosome fusion is preceded by tethering that probably requires mammalian orthologues of the yeast HOPS (homotypic fusion and vacuole protein sorting) complex. Heterotypic late endosome–lysosome membrane fusion is mediated by a trans-SNARE (soluble N-ethylmaleimide-sensitive factor-attachment protein receptor) complex comprising Syntaxin7, Vti1b, Syntaxin8 and VAMP7 (vesicle-associated membrane protein 7). This differs from the trans-SNARE complex required for homotypic late endosome fusion in which VAMP8 replaces VAMP7. VAMP7 is also required for lysosome fusion with the plasma membrane and its retrieval from the plasma membrane to lysosomes is mediated by its folded N-terminal longin domain. Co-ordinated interaction of the ESCRT, HOPS and SNARE complexes is required for cargo delivery to lysosomes.

Plasma membrane targetting, vesicular budding and release of galectin 3 from the cytoplasm of mammalian cells during secretion

1997 ◽  
Vol 110 (10) ◽  
pp. 1169-1178 ◽  
Author(s):  
B. Mehul ◽  
R.C. Hughes
Keyword(s):  
Plasma Membrane ◽  
Mammalian Cells ◽  
Protein Tyrosine Kinase ◽  
Signal Sequence ◽  
Buoyant Density ◽  
Membrane Domains ◽  
Transfected Cells ◽  
Amino Terminal ◽  
Galectin 3 ◽  
Plasma Membrane Domains

Galectin 3, a 30 kDa galactoside-binding protein distributed widely in epithelial and immune cells, contains no signal sequence and is externalized by a mechanism independent of the endoplasmic reticulum (ER)-Golgi complex. We show here that hamster galectin 3 overexpressed in transfected cos-7 cells is secreted at a very low rate. A chimaera of galectin 3 fused to the N-terminal acylation sequence of protein tyrosine kinase p56(lck), Nt-p56(lck)-galectin 3, which is myristoylated and palmitoylated and rapidly transported to plasma membrane domains, is efficiently released from transfected cells indicating that movement of cytoplasmic galectin 3 to plasma membrane domains is a rate limiting step in lectin secretion. N-terminal acylation is not sufficient for protein secretion since p56(lck) and the chimaera Nt-p56(lck)-CAT are not secreted from transfected cells. The amino-terminal half of galectin 3 is sufficient to direct export of a chimaeric CAT protein indicating that part of the signal for plasma membrane translocation lies in the N-terminal domains of the lectin. Immunofluorescence studies show that Nt-p56(lck)-galectin 3 aggregates underneath the plasma membrane and is released by membrane blebbing. Vesicles of low buoyant density isolated from conditioned medium are enriched in galectin 3. The lectin is initially protected from exogenous collagenase but is later released in soluble protease-sensitive form from the lectin-loaded vesicles. Using murine macrophages, which secrete their endogenous galectin 3 at a moderate rate especially in the presence of Ca2+-ionophores, we were also able to trap a galectin 3-loaded vesicular fraction which was released into the culture supernatant.

scholarly journals Open Reading Frame 1 of the Norwalk-Like Virus Camberwell: Completion of Sequence and Expression in Mammalian Cells

1999 ◽  
Vol 73 (12) ◽  
pp. 10531-10535 ◽  
Author(s):  
Ee Ling Seah ◽  
John A. Marshall ◽  
Peter J. Wright
Keyword(s):  
Mammalian Cells ◽  
Simian Virus 40 ◽  
Viral Proteins ◽  
Simian Virus ◽  
Cleavage Sites ◽  
Full Genome ◽  
Reading Frame ◽  
Cos Cells ◽  
Expression In Mammalian Cells ◽  
Open Reading Frame 1

ABSTRACT The ORF1 sequence was determined for Camberwell virus, a genogroup 2 Norwalk-like virus, completing the full genome of 7,555 nucleotides. ORF1 cDNA was cloned into a simian virus 40-based expression vector, and the viral proteins synthesized following transfection into COS cells were analyzed. By using antisera directed against the helicase, protease, or polymerase regions, eight polypeptides ranging in size from 19 to 117 kDa were detected by radioimmunoprecipitation. The cleavage sites determining the amino and carboxy termini of the 3C-like protease were identified at E1008/A and E1189/G, respectively.

scholarly journals The effects of Mitogenic and Metabolic cues on clathrin-mediated endocytosis

2021 ◽  
Author(s):  
Ralph Christian Delos Santos
Keyword(s):  
Plasma Membrane ◽  
Mammalian Cells ◽  
Energy Levels ◽  
Surface Proteins ◽  
Coated Pits ◽  
Calcium Signals ◽  
Cellular Energy ◽  
Software Analysis ◽  
Cellular Processes ◽  
Automated Software

The cell ‘surfaceome’ collectively describes proteins found on the plasma membrane (PM), which functions in fundamental cellular processes including growth and proliferation. The surfaceome undergoes dynamic remodeling via the addition/removal of surface proteins in response to changing environmental conditions. In mammalian cells, surfaceome remodeling is predominantly facilitated by clathrin-mediated endocytosis (CME) which involves the invagination and internalization of PM regions via clathrin-coated structures—removing proteins from the cell surface. As a major regulator of the surfaceome, it is important to understand the underlying mechanisms governing CME, given that its dysregulation has been implicated in human pathologies including neurologic and oncogenic disorders. Cellular cues including mitogenic (e.g. growth factors) and metabolic signals (e.g. cellular energy levels) induce diverse cellular processes (e.g. growth and proliferation) requiring surfaceome/PM remodeling. Precisely how mitogenic and metabolic signals may induce surfaceome remodeling however, is under-examined. As a major regulator of the surfaceome, CME is a likely mechanism through which cellular cues may remodel the PM. Poorly understood, I thus sought to investigate how mitogenic and metabolic signals may regulate CME. Mitogenic signaling by the epidermal growth factor receptor (EGFR) triggers PLCγ1-calcium signals, which I found a requirement for CME of EGFR—likely via calcium control of the Sjn1 protein. Consistently, using TIRF-M imaging coupled to automated software analysis, I demonstrate that inhibition of PLCγ1-calcium signals impairs the formation/assembly of GFR-containing clathrin structures. In addition, I hypothesize that PLCγ1-calcium signals also regulates the CME of other surface proteins given its robust control of Sjn1—which localizes broadly amongst clathrin-coated structures. AMPK is a cellular energy sensor activated by metabolic stress (e.g. starvation). Using TIRF-M imaging coupled to automated software analysis, I found that AMPK activation broadly reduces the formation/assembly of bona fide clathrin-coated pits, without impairing the internalization rates of CME cargoes (e.g. EGFR, TfR and β1-integrin). Furthermore, I found that AMPK may regulate CME throughcontrol of the Arf6 protein. Collectively, my findings uncover and provide novel mechanisms by which mitogenic (via EGFR-induced calcium signals) and metabolic signals (via AMPK control of Arf6) may induce regulation of CME—in eliciting global reorganization of the plasma membrane. 1,2,11–13,3–10

scholarly journals The effects of Mitogenic and Metabolic cues on clathrin-mediated endocytosis

2021 ◽  
Author(s):  
Ralph Christian Delos Santos
Keyword(s):  
Plasma Membrane ◽  
Mammalian Cells ◽  
Energy Levels ◽  
Surface Proteins ◽  
Coated Pits ◽  
Calcium Signals ◽  
Cellular Energy ◽  
Software Analysis ◽  
Cellular Processes ◽  
Automated Software

The cell ‘surfaceome’ collectively describes proteins found on the plasma membrane (PM), which functions in fundamental cellular processes including growth and proliferation. The surfaceome undergoes dynamic remodeling via the addition/removal of surface proteins in response to changing environmental conditions. In mammalian cells, surfaceome remodeling is predominantly facilitated by clathrin-mediated endocytosis (CME) which involves the invagination and internalization of PM regions via clathrin-coated structures—removing proteins from the cell surface. As a major regulator of the surfaceome, it is important to understand the underlying mechanisms governing CME, given that its dysregulation has been implicated in human pathologies including neurologic and oncogenic disorders. Cellular cues including mitogenic (e.g. growth factors) and metabolic signals (e.g. cellular energy levels) induce diverse cellular processes (e.g. growth and proliferation) requiring surfaceome/PM remodeling. Precisely how mitogenic and metabolic signals may induce surfaceome remodeling however, is under-examined. As a major regulator of the surfaceome, CME is a likely mechanism through which cellular cues may remodel the PM. Poorly understood, I thus sought to investigate how mitogenic and metabolic signals may regulate CME. Mitogenic signaling by the epidermal growth factor receptor (EGFR) triggers PLCγ1-calcium signals, which I found a requirement for CME of EGFR—likely via calcium control of the Sjn1 protein. Consistently, using TIRF-M imaging coupled to automated software analysis, I demonstrate that inhibition of PLCγ1-calcium signals impairs the formation/assembly of GFR-containing clathrin structures. In addition, I hypothesize that PLCγ1-calcium signals also regulates the CME of other surface proteins given its robust control of Sjn1—which localizes broadly amongst clathrin-coated structures. AMPK is a cellular energy sensor activated by metabolic stress (e.g. starvation). Using TIRF-M imaging coupled to automated software analysis, I found that AMPK activation broadly reduces the formation/assembly of bona fide clathrin-coated pits, without impairing the internalization rates of CME cargoes (e.g. EGFR, TfR and β1-integrin). Furthermore, I found that AMPK may regulate CME throughcontrol of the Arf6 protein. Collectively, my findings uncover and provide novel mechanisms by which mitogenic (via EGFR-induced calcium signals) and metabolic signals (via AMPK control of Arf6) may induce regulation of CME—in eliciting global reorganization of the plasma membrane. 1,2,11–13,3–10

scholarly journals Phosphoinositide–Ap-2 Interactions Required for Targeting to Plasma Membrane Clathrin-Coated Pits

1999 ◽  
Vol 146 (4) ◽  
pp. 755-764 ◽  
Author(s):  
Ibragim Gaidarov ◽  
James H. Keen
Keyword(s):  
Plasma Membrane ◽  
Mammalian Cells ◽  
Limited Proteolysis ◽  
Adaptor Protein ◽  
Dominant Negative ◽  
Coated Pits ◽  
Intact Cells ◽  
Α Subunit ◽  
General Role ◽  
Receptor Complexes

The clathrin-associated AP-2 adaptor protein is a major polyphosphoinositide-binding protein in mammalian cells. A high affinity binding site has previously been localized to the NH2-terminal region of the AP-2 α subunit (Gaidarov et al. 1996. J. Biol. Chem. 271:20922–20929). Here we used deletion and site- directed mutagenesis to determine that α residues 21–80 comprise a discrete folding and inositide-binding domain. Further, positively charged residues located within this region are involved in binding, with a lysine triad at positions 55–57 particularly critical. Mutant peptides and protein in which these residues were changed to glutamine retained wild-type structural and functional characteristics by several criteria including circular dichroism spectra, resistance to limited proteolysis, and clathrin binding activity. When expressed in intact cells, mutated α subunit showed defective localization to clathrin-coated pits; at high expression levels, the appearance of endogenous AP-2 in coated pits was also blocked consistent with a dominant-negative phenotype. These results, together with recent work indicating that phosphoinositides are also critical to ligand-dependent recruitment of arrestin-receptor complexes to coated pits (Gaidarov et al. 1999. EMBO (Eur. Mol. Biol. Organ.) J. 18:871–881), suggest that phosphoinositides play a critical and general role in adaptor incorporation into plasma membrane clathrin-coated pits.

Changes Occur in Plasma Membrane Turnover when K562 Leukemia Cells are Induced to Differentiate

1982 ◽  
Vol 40 ◽  
pp. 286-287
Author(s):  
L. M. Marshall
Keyword(s):  
Plasma Membrane ◽  
Membrane Proteins ◽  
Intracellular Transport ◽  
Parent Cell ◽  
Membrane Turnover ◽  
Coated Pits ◽  
Surface Distribution ◽  
Specific Proteins ◽  
Erythroleukemic Cell ◽  
Specific Membrane

A human erythroleukemic cell line, metabolically blocked in a late stage of erythropoiesis, becomes capable of differentiation along the normal pathway when grown in the presence of hemin. This process is characterized by hemoglobin synthesis followed by rearrangement of the plasma membrane proteins and culminates in asymmetrical cytokinesis in the absence of nuclear division. A reticulocyte-like cell buds from the nucleus-containing parent cell after erythrocyte specific membrane proteins have been sequestered into its membrane. In this process the parent cell faces two obstacles. First, to organize its erythrocyte specific proteins at one pole of the cell for inclusion in the reticulocyte; second, to reduce or abolish membrane protein turnover since hemoglobin is virtually the only protein being synthesized at this stage. A means of achieving redistribution and cessation of turnover could involve movement of membrane proteins by a directional lipid flow. Generation of a lipid flow towards one pole and accumulation of erythrocyte-specific membrane proteins could be achieved by clathrin coated pits which are implicated in membrane endocytosis, intracellular transport and turnover. In non-differentiating cells, membrane proteins are turned over and are random in surface distribution. If, however, the erythrocyte specific proteins in differentiating cells were excluded from endocytosing coated pits, not only would their turnover cease, but they would also tend to drift towards and collect at the site of endocytosis. This hypothesis requires that different protein species are endocytosed by the coated vesicles in non-differentiating than by differentiating cells.

Caveolin-1, galectin-3 and lipid raft domains in cancer cell signalling

2015 ◽  
Vol 57 ◽  
pp. 189-201 ◽  
Author(s):  
Jay Shankar ◽  
Cecile Boscher ◽  
Ivan R. Nabi
Keyword(s):  
Plasma Membrane ◽  
Lipid Rafts ◽  
Cancer Cell ◽  
Cellular Response ◽  
Spatial Organization ◽  
Essential Feature ◽  
Cell Signalling ◽  
Coated Pits ◽  
Signalling Molecules ◽  
Raft Domains

Spatial organization of the plasma membrane is an essential feature of the cellular response to external stimuli. Receptor organization at the cell surface mediates transmission of extracellular stimuli to intracellular signalling molecules and effectors that impact various cellular processes including cell differentiation, metabolism, growth, migration and apoptosis. Membrane domains include morphologically distinct plasma membrane invaginations such as clathrin-coated pits and caveolae, but also less well-defined domains such as lipid rafts and the galectin lattice. In the present chapter, we will discuss interaction between caveolae, lipid rafts and the galectin lattice in the control of cancer cell signalling.

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