scholarly journals Domains of the Rsp5 Ubiquitin-Protein Ligase Required for Receptor-mediated and Fluid-Phase Endocytosis

2001 ◽  
Vol 12 (2) ◽  
pp. 421-435 ◽  
Author(s):  
Rebecca Dunn ◽  
Linda Hicke
Keyword(s):  
Plasma Membrane ◽  
Point Mutations ◽  
Fluid Phase ◽  
Endocytic Pathway ◽  
Receptor Internalization ◽  
Temperature Sensitive ◽  
C2 Domain ◽  
Ww Domains ◽  
Amino Terminal ◽  
Regulatory Event

Yeast Rsp5p and its mammalian homologue, Nedd4, arehect domain ubiquitin-protein ligases (E3s) required for the ubiquitin-dependent endocytosis of plasma membrane proteins. Because ubiquitination is sufficient to induce internalization, E3-mediated ubiquitination is a key regulatory event in plasma membrane protein endocytosis. Rsp5p is an essential, multidomain protein containing an amino-terminal C2 domain, three WW protein-protein interaction domains, and a carboxy-terminal hect domain that carries E3 activity. In this study, we demonstrate that Rsp5p is peripherally associated with membranes and provide evidence that Rsp5p functions as part of a multimeric protein complex. We define the function of Rsp5p and its domains in the ubiquitin-dependent internalization of the yeast α-factor receptor, Ste2p. Temperature-sensitive rsp5 mutants were unable to ubiquitinate or to internalize Ste2p at the nonpermissive temperature. Deletion of the entire C2 domain had no effect on α-factor internalization; however, point mutations in any of the three WW domains impaired both receptor ubiquitination and internalization. These observations indicate that the WW domains play a role in the important regulatory event of selecting phosphorylated proteins as endocytic cargo. In addition, mutations in the C2 and WW1 domains had more severe defects on transport of fluid-phase markers to the vacuole than on receptor internalization, suggesting that Rsp5p functions at multiple steps in the endocytic pathway.

scholarly journals Recycling pathways of glucosylceramide in BHK cells: distinct involvement of early and late endosomes

1992 ◽  
Vol 103 (4) ◽  
pp. 1139-1152
Author(s):  
J.W. Kok ◽  
K. Hoekstra ◽  
S. Eskelinen ◽  
D. Hoekstra
Keyword(s):  
Plasma Membrane ◽  
Intracellular Ph ◽  
Brefeldin A ◽  
Fluid Phase ◽  
Endocytic Pathway ◽  
Late Endosomes ◽  
Early Endosomes ◽  
Recycling Pathway ◽  
Golgi Network ◽  
Extensive Involvement

Recycling pathways of the sphingolipid glucosylceramide were studied by employing a fluorescent analog of glucosylceramide, 6(-)[N-(7-nitro-2,1,3-benzoxadiazol-4-yl)amino]hexanoylglucosyl sphingosine (C6-NBD-glucosylceramide). Direct recycling of the glycolipid from early endosomes to the plasma membrane occurs, as could be shown after treating the cells with the microtubule-disrupting agent nocodazole, which causes inhibition of the glycolipid's trafficking from peripheral early endosomes to centrally located late endosomes. When the microtubuli are intact, at least part of the glucosylceramide is transported from early to late endosomes together with ricin. Interestingly, also N-(lissamine rhodamine B sulfonyl)phosphatidylethanolamine (N-Rh-PE), a membrane marker of the fluid-phase endocytic pathway, is transported to this endosomal compartment. However, in contrast to both ricin and N-Rh-PE, the glucosylceramide can escape from this organelle and recycle to the plasma membrane. Monensin and brefeldin A have little effect on this recycling pathway, which would exclude extensive involvement of early Golgi compartments in recycling. Hence, the small fraction of the glycolipid that colocalizes with transferrin (Tf) in the Golgi area might directly recycle via the trans-Golgi network. When the intracellular pH was lowered to 5.5, recycling was drastically reduced, in accordance with the impeding effect of low intracellular pH on vesicular transport during endocytosis and in the biosynthetic pathway. Our results thus demonstrate the existence of at least two recycling pathways for glucosylceramide and indicate the relevance of early endosomes in recycling of both proteins and lipids.

Ligand-stimulated beta 2-adrenergic receptor internalization via the constitutive endocytic pathway into rab5-containing endosomes

1995 ◽  
Vol 108 (9) ◽  
pp. 2983-2991 ◽  
Author(s):  
R.H. Moore ◽  
N. Sadovnikoff ◽  
S. Hoffenberg ◽  
S. Liu ◽  
P. Woodford ◽  
...  
Keyword(s):  
Transferrin Receptor ◽  
Adrenergic Receptor ◽  
Fluid Phase ◽  
Small Gtpase ◽  
Endocytic Pathway ◽  
Receptor Internalization ◽  
Beta Agonist ◽  
Hek293 Cells ◽  
Fluid Phase Endocytosis ◽  
Beta 2

The small GTPase rab5 appears to be rate-limiting for the constitutive internalization of transferrin receptor and for fluid-phase endocytosis. However, it is unknown whether rab5 regulates receptors whose internalization is stimulated by the binding of ligand, and whether such receptors change the underlying rate of the endocytic pathways they utilize. As a model for ligand-stimulated endocytosis, we used transfected HEK293 cells expressing high levels of an epitope-tagged human beta 2-adrenergic receptor. Nearly all receptors were on the cell surface in the absence of agonist, but within ten minutes of agonist addition > 50% of receptors internalized and colocalized extensively with rab5. Hypertonic sucrose blocked beta 2-adrenergic receptor internalization, as well as that of transferrin receptor, suggesting a clathrin-mediated process. In contrast, an inhibitor of potocytosis had little effect upon beta 2-adrenergic receptor internalization, suggesting that this process did not require active caveolae. Consistent with this finding, caveolin was not detectable in the 12 beta 6 line, as assessed by western blotting with a polyclonal anti-caveolin antibody. Stimulated receptor internalization did not affect the rate or capacity of the constitutive endocytic pathway since there was no detectable increase in fluid-phase endocytosis after addition of beta-agonist, nor was there a significant change in the amount of surface transferrin receptor. Altogether, these data suggest that beta 2-adrenergic receptors internalize by a clathrin-mediated and rab5-regulated constitutive endocytic pathway. Further, agonist-stimulated receptor internalization has no detectable effect upon the function of this pathway.

scholarly journals Yeast P4-ATPases Drs2p and Dnf1p Are Essential Cargos of the NPFXD/Sla1p Endocytic Pathway

2007 ◽  
Vol 18 (2) ◽  
pp. 487-500 ◽  
Author(s):  
Ke Liu ◽  
Zhaolin Hua ◽  
Joshua A. Nepute ◽  
Todd R. Graham
Keyword(s):  
Plasma Membrane ◽  
Protein Transport ◽  
Endocytic Pathway ◽  
Temperature Sensitive ◽  
Wild Type ◽  
Sensitive Mutant ◽  
C Terminus ◽  
P Type ◽  
Golgi Network ◽  
Endocytic Pathways

Drs2p family P-type ATPases (P4-ATPases) are required in multiple vesicle-mediated protein transport steps and are proposed to be phospholipid translocases (flippases). The P4-ATPases Drs2p and Dnf1p cycle between the exocytic and endocytic pathways, and here we define endocytosis signals required by these proteins to maintain a steady-state localization to internal organelles. Internalization of Dnf1p from the plasma membrane uses an NPFXD endocytosis signal and its recognition by Sla1p, part of an endocytic coat/adaptor complex with clathrin, Pan1p, Sla2p/End4p, and End3p. Drs2p has multiple endocytosis signals, including two NPFXDs near the C terminus and PEST-like sequences near the N terminus that may mediate ubiquitin (Ub)-dependent endocytosis. Drs2p localizes to the trans-Golgi network in wild-type cells and accumulates on the plasma membrane when both the Ub- and NPFXD-dependent endocytic mechanisms are inactivated. Surprisingly, the pan1-20 temperature-sensitive mutant is constitutively defective for Ub-dependent endocytosis but is not defective for NPFXD-dependent endocytosis at the permissive growth temperature. To sustain viability of pan1-20, Drs2p must be endocytosed through the NPFXD/Sla1p pathway. Thus, Drs2p is an essential endocytic cargo in cells compromised for Ub-dependent endocytosis. These results demonstrate an essential role for endocytosis in retrieving proteins back to the Golgi, and they define critical cargos of the NPFXD/Sla1p system.

scholarly journals Nef-mediated Clathrin-coated Pit Formation

1997 ◽  
Vol 139 (1) ◽  
pp. 37-47 ◽  
Author(s):  
Michelangelo Foti ◽  
Aram Mangasarian ◽  
Vincent Piguet ◽  
Daniel P. Lew ◽  
Karl-Heinz Krause ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Cytoplasmic Tail ◽  
Fluid Phase ◽  
Receptor Internalization ◽  
Coat Proteins ◽  
Membrane Area ◽  
Sequence Of Events ◽  
Early Protein ◽  
Functional Consequences ◽  
Cluster Of Differentiation

The sequence of events leading to clathrin-coated pit (CCP) nucleation on the cell surface and to the incorporation of receptors into these endocytic structures is still imperfectly understood. In particular, the question remains as to whether receptor tails initiate the assembly of the coat proteins or whether receptors migrate into preformed CCP. This question was approached through a dissection of the mechanisms implemented by Nef, an early protein of human and simian immunodeficiency virus (HIV and SIV, respectively), to accelerate the endocytosis of cluster of differentiation antigen type 4 (CD4), the major receptor for these viruses. Results collected showed that: (a) Nef promotes CD4 internalization via an increased association of CD4 with CCP; (b) the Nef-mediated increase of CD4 association with CCP is related to a doubling of the plasma membrane area occupied by clathrin-coated structures; (c) this increased CCP number at the plasma membrane has functional consequences preferentially on CD4 uptake and does not significantly affect transferrin receptor internalization or fluid-phase endocytosis; (d) the presence of a CD4 cytoplasmic tail including a critical dileucine motif is required to induce CCP formation via Nef; and (e) when directly anchored to the cytoplasmic side of the plasma membrane, Nef itself can promote CCP formation. Taken together, these observations lead us to propose that CD4 can promote CCP generation via the connector molecule Nef. In this model, Nef interacts on one side with CD4 through a dileucine-based motif present on CD4 cytoplasmic tail and on the other side with components of clathrin-coated surface domain (i.e., adaptins). These Nef-generated complexes would then initiate the nucleation of CCP.

scholarly journals A Myosin I Is Involved in Membrane Recycling from Early Endosomes

2000 ◽  
Vol 150 (5) ◽  
pp. 1013-1026 ◽  
Author(s):  
Eva M. Neuhaus ◽  
Thierry Soldati
Keyword(s):  
Plasma Membrane ◽  
Fluid Phase ◽  
Surface Proteins ◽  
Endocytic Pathway ◽  
Membrane Recycling ◽  
Myosin I ◽  
Early Endosomes ◽  
Butanedione Monoxime ◽  
Microscopy Method ◽  
Membrane Components

Geometry-based mechanisms have been proposed to account for the sorting of membranes and fluid phase in the endocytic pathway, yet little is known about the involvement of the actin–myosin cytoskeleton. Here, we demonstrate that Dictyostelium discoideum myosin IB functions in the recycling of plasma membrane components from endosomes back to the cell surface. Cells lacking MyoB (myoA−/B−, and myoB− cells) and wild-type cells treated with the myosin inhibitor butanedione monoxime accumulated a plasma membrane marker and biotinylated surface proteins on intracellular endocytic vacuoles. An assay based on reversible biotinylation of plasma membrane proteins demonstrated that recycling of membrane components is severely impaired in myoA/B null cells. In addition, MyoB was specifically found on magnetically purified early pinosomes. Using a rapid-freezing cryoelectron microscopy method, we observed an increased number of small vesicles tethered to relatively early endocytic vacuoles in myoA−/B− cells, but not to later endosomes and lysosomes. This accumulation of vesicles suggests that the defects in membrane recycling result from a disordered morphology of the sorting compartment.

scholarly journals Eps15 Is Recruited to the Plasma Membrane upon Epidermal Growth Factor Receptor Activation and Localizes to Components of the Endocytic Pathway during Receptor Internalization

1999 ◽  
Vol 10 (2) ◽  
pp. 417-434 ◽  
Author(s):  
Maria Rosaria Torrisi ◽  
Lavinia Vittoria Lotti ◽  
Francesca Belleudi ◽  
Roberto Gradini ◽  
Anna Elisabetta Salcini ◽  
...  
Keyword(s):  
Epidermal Growth Factor Receptor ◽  
Plasma Membrane ◽  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Growth Factor Receptor ◽  
Adaptor Protein ◽  
Receptor Activation ◽  
Endocytic Pathway ◽  
Receptor Internalization ◽  
Epidermal Growth

Eps15 is a substrate for the tyrosine kinase of the epidermal growth factor receptor (EGFR) and is characterized by the presence of a novel protein:protein interaction domain, the EH domain. Eps15 also stably binds the clathrin adaptor protein complex AP-2. Previous work demonstrated an essential role for eps15 in receptor-mediated endocytosis. In this study we show that, upon activation of the EGFR kinase, eps15 undergoes dramatic relocalization consisting of 1) initial relocalization to the plasma membrane and 2) subsequent colocalization with the EGFR in various intracellular compartments of the endocytic pathway, with the notable exclusion of coated vesicles. Relocalization of eps15 is independent of its binding to the EGFR or of binding of the receptor to AP-2. Furthermore, eps15 appears to undergo tyrosine phosphorylation both at the plasma membrane and in a nocodazole-sensitive compartment, suggesting sustained phosphorylation in endocytic compartments. Our results are consistent with a model in which eps15 undergoes cycles of association:dissociation with membranes and suggest multiple roles for this protein in the endocytic pathway.

scholarly journals The C2 domain of the ubiquitin ligase Rsp5 is required for ubiquitination of the endocytic protein Rvs167 upon change of nitrogen source

2020 ◽  
Vol 20 (7) ◽  
Author(s):  
Ryoya Tanahashi ◽  
Tira Siti Nur Afiah ◽  
Akira Nishimura ◽  
Daisuke Watanabe ◽  
Hiroshi Takagi
Keyword(s):  
Plasma Membrane ◽  
Amino Acid ◽  
Nitrogen Source ◽  
Ubiquitin Ligase ◽  
Membrane Binding ◽  
C2 Domain ◽  
Amino Acid Permease ◽  
Amino Terminal ◽  
Endocytic Protein ◽  
Biochemical Analyses

ABSTRACT Ubiquitination is a key signal for endocytosis of proteins on the plasma membrane. The ubiquitin ligase Rsp5 of Saccharomyces cerevisiae, which contains an amino-terminal membrane-binding C2 domain, three substrate-recognizing tryptophan-tryptophan (WW) domains and a carboxyl-terminal catalytic homologous to the E6-AP carboxyl terminus (HECT) domain, can ubiquitinate plasma membrane proteins directing them for endocytosis. Here, we examined the roles of the C2 domain in endocytosis for the downregulation of the general amino acid permease Gap1, which is one of nitrogen-regulated permeases in S. cerevisiae. First, we constructed several rsp5 mutants producing Rsp5 variants without the C2 domain or with amino acid changes of membrane-binding lysine residues. These mutants showed defects in endocytosis of Gap1 in response to a preferred nitrogen source. Intriguingly, we found that ubiquitination of Gap1 in these mutant cells was highly similar to that in wild-type cells during endocytosis. These results indicate that the C2 domain is essential for endocytosis but not for ubiquitination of substrates such as Gap1. Moreover, genetic and biochemical analyses showed that the endocytic protein Rvs167 was ubiquitinated via Rsp5 and the C2 domain was required for efficient ubiquitination in response to a preferred nitrogen source. Here, we propose a mechanism for the C2 domain-mediated endocytosis of plasma membrane permeases.

Traffic to the endocytic compartment of plants

1989 ◽  
Vol 47 ◽  
pp. 754-755
Author(s):  
L. R. Griffing ◽  
R. D. Record ◽  
H. H. Mollenhauer
Keyword(s):  
Plasma Membrane ◽  
Golgi Complex ◽  
Fluid Phase ◽  
Multivesicular Body ◽  
Endocytic Pathway ◽  
Cationized Ferritin ◽  
Plant Protoplasts ◽  
Whole Cells ◽  
Membrane Bound ◽  
And Function

The endocytic pathway of plants has been identified and partially characterized using nonspecific membrane-bound and fluid phase probes . The function of endocytosis in plants is, however, unknown. We shall describe how ultrastructural histochemistry, immunocytochemical analyses and fluorescence imaging have been used to explore the physiology and function of the endocytic pathway in plant protoplasts and whole cells.Cationized ferritin (CF) can be used as a marker of plasma membrane uptake in plant protoplasts. Several different organelles become labeled upon exposure of protoplasts to CF: clathrin-coated vesicles (CV), the partially coated reticulum (PCR), the Golgi complex (GC), the multivesicular body (MVB), and the vacuole (V). These organelles also participate in the pathways of secretion and delivery of protein to the lysosome (vacuole). What are the sites of overlap/divergence among the secretory, endocytic and lysosomal pathways in these cells?

An LI and ML motif in the cytoplasmic tail of the MHC-associated invariant chain mediate rapid internalization

1994 ◽  
Vol 107 (7) ◽  
pp. 2021-2032 ◽  
Author(s):  
B. Bremnes ◽  
T. Madsen ◽  
M. Gedde-Dahl ◽  
O. Bakke
Keyword(s):  
Plasma Membrane ◽  
Mhc Class Ii ◽  
Transmembrane Protein ◽  
Point Mutations ◽  
Cytoplasmic Tail ◽  
Class Ii ◽  
Endocytic Pathway ◽  
Invariant Chain ◽  
Chimeric Proteins ◽  
Endosomal Pathway

Invariant chain (Ii) is a transmembrane protein that associates with the MHC class II molecules in the endoplasmic reticulum. Two regions of the 30 residue cytoplasmic tail of Ii contain sorting information able to direct Ii to the endocytic pathway. The full-length cytoplasmic tail of Ii and the two tail regions were fused to neuraminidase (NA) forming chimeric proteins (INA). Ii is known to form trimers and when INA was transfected into COS cells it assembled as a tetramer like NA. The INA molecules were targeted to the endosomal pathway and cotransfection with Ii showed that both molecules appeared in the same vesicles. By labelling the INA fusion proteins with iodinated antibody it was found that molecules with either endocytosis signal were expressed at the plasma membrane and internalized rapidly. Point mutations revealed that an LI motif within the first region of the cytoplasmic tail and an ML motif in the second region were essential for efficient internalization. The region containing the LI motif is required for Ii to induce large endosomes but a functional LI internalization motif was not fundamental for this property. The cytoplasmic tail of Ii is essential for efficient targeting of the class II molecules to endosomes and the dual LI and ML motif may thus be responsible for directing these molecules to the endosomal pathway, possibly via the plasma membrane.

The contractile vacuole network of Dictyostelium as a distinct organelle: its dynamics visualized by a GFP marker protein

1999 ◽  
Vol 112 (22) ◽  
pp. 3995-4005 ◽  
Author(s):  
D. Gabriel ◽  
U. Hacker ◽  
J. Kohler ◽  
A. Muller-Taubenberger ◽  
J.M. Schwartz ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Transmembrane Protein ◽  
Fluid Phase ◽  
Endocytic Pathway ◽  
Contractile Vacuole ◽  
Specific Marker ◽  
Sharp Separation ◽  
Cell Fractions ◽  
Entire Network

The contractile vacuole system is an osmoregulatory organelle composed of cisternae and interconnecting ducts. Large cisternae act as bladders that periodically fuse with the plasma membrane, forming pores to expel water. To visualize the entire network in vivo and to identify constituents of the vacuolar complex in cell fractions, we introduced a specific marker into Dictyostelium cells, GFP-tagged dajumin. The C-terminal, GFP-tagged region of this transmembrane protein is responsible for sorting to the contractile vacuole complex. Dajumin-GFP negligibly associates with the plasma membrane, indicating its retention during discharge of the bladder. Fluorescent labeled cell-surface constituents are efficiently internalized by endocytosis, while no significant cycling through the contractile vacuole is observed. Endosomes loaded with yeast particles or a fluid-phase marker indicate sharp separation of the endocytic pathway from the contractile vacuole compartment. Even after dispersion of the contractile vacuole system during mitosis, dajumin-GFP distinguishes the vesicles from endosomes, and visualizes post-mitotic re-organization of the network around the nucleus. Highly discriminative sorting and membrane fusion mechanisms are proposed to account for the sharp separation of the contractile vacuole and endosomal compartments. Evidence for a similar compartment in other eukaryotic cells is discussed.

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