scholarly journals In migrating fibroblasts, recycling receptors are concentrated in narrow tubules in the pericentriolar area, and then routed to the plasma membrane of the leading lamella.

1994 ◽  
Vol 125 (6) ◽  
pp. 1265-1274 ◽  
Author(s):  
C R Hopkins ◽  
A Gibson ◽  
M Shipman ◽  
D K Strickland ◽  
I S Trowbridge
Keyword(s):  
Plasma Membrane ◽  
Chick Embryo ◽  
Cell Surface ◽  
Transferrin Receptor ◽  
Transferrin Receptors ◽  
Intracellular Processing ◽  
Recycling Pathway ◽  
Embryo Fibroblasts ◽  
Migrating Cells

By following the intracellular processing of recycling transferrin receptors and the selective sorting of a-2 macroglobulin in chick embryo fibroblasts, we have shown that the concentration of 60 nm diam tubules which surrounds the centrioles represents a distal compartment on the recycling pathway. In migrating cells transferrin receptor tracers can be loaded into this compartment and then chased to the cell surface. When they emerge the recycling transferrin receptors are distributed over the surface of the leading lamella.

scholarly journals Rapid endocytosis of the transferrin receptor in the absence of bound transferrin.

1985 ◽  
Vol 100 (2) ◽  
pp. 633-637 ◽  
Author(s):  
C Watts
Keyword(s):  
Cell Surface ◽  
Ligand Binding ◽  
Cell Line ◽  
Transferrin Receptor ◽  
Protein A ◽  
Transferrin Receptors ◽  
Coated Pits ◽  
Prolonged Incubation ◽  
Surface Receptors ◽  
Recycling Pathway

The rate of endocytosis of transferrin receptors, occupied or unoccupied with transferrin, was measured on the cell line K562. At 37 degrees C, receptors, radioiodinated on the cell surface at 4 degrees C, were internalized equally rapidly in the presence or absence of transferrin. In both cases, 50% of the labeled receptors became resistant to externally added trypsin in 5 min. An antitransferrin antibody was used to show directly that the receptors had entered the cells without bound transferrin. The distribution of the receptors on the cell surface was revealed by antibody and protein A-gold staining after prolonged incubation in the presence or absence of transferrin. The receptors were concentrated in coated pits under both conditions. The data suggest that endocytosis of transferrin receptors is not "triggered" by ligand binding and raise the possibility that ligand-induced down-regulation of surface receptors may not occur by this mechanism. Instead receptors may be recognized as being ligand-occupied, not at the cell surface, but at some other site in the recycling pathway such as the endosome.

scholarly journals Phorbol ester treatment increases the exocytic rate of the transferrin receptor recycling pathway independent of serine-24 phosphorylation.

1988 ◽  
Vol 106 (4) ◽  
pp. 1061-1066 ◽  
Author(s):  
T E McGraw ◽  
K W Dunn ◽  
F R Maxfield
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Cell Surface ◽  
Phorbol Ester ◽  
Cho Cells ◽  
Transferrin Receptor ◽  
Phosphorylation Site ◽  
Major Protein ◽  
Kinase C ◽  
Recycling Pathway

In Chinese hamster ovary (CHO) fibroblast cells the protein kinase C activating phorbol ester, phorbol myristate acetate (PMA), stimulates an increase in cell surface transferrin receptor (TR) expression by increasing the exocytic rate of the recycling pathway. The human TR expressed in CHO cells is similarly affected by PMA treatment. A mutant human TR in which the major protein kinase C phosphorylation site, serine 24, has been replaced with the non-phosphorylatable amino acid glycine has been constructed to investigate the role of receptor phosphorylation in the PMA induced up-regulation. The Gly-24-substituted receptor binds, internalizes, and recycles Tf. Furthermore, the altered receptor mediates cellular Fe accumulation from diferric-Tf, thereby fulfilling the receptor's major biological role. The Gly-24 TR behaves identically to the wild-type TR when cells are treated with PMA. Therefore, Ser-24 phosphorylation is not required for the PMA-induced redistribution of the human TR expressed in CHO cells. The increased TR expression on the cell surface after PMA treatment results from an increase in the rate of exocytosis of the recycling receptors. No change in the endocytic rate or the size of the recycling receptor pool was observed. These results indicate that the PMA effect on the TR surface expression may result from a more general perturbation of membrane trafficking rather than a specific modulation of the TR.

scholarly journals A novel class of clathrin-coated vesicles budding from endosomes.

1996 ◽  
Vol 132 (1) ◽  
pp. 21-33 ◽  
Author(s):  
W Stoorvogel ◽  
V Oorschot ◽  
H J Geuze
Keyword(s):  
Plasma Membrane ◽  
Microscopic Examination ◽  
Transferrin Receptor ◽  
Brefeldin A ◽  
Coated Vesicles ◽  
Integral Membrane Proteins ◽  
Transferrin Receptors ◽  
Receptor Recycling ◽  
Coated Pits ◽  
Novel Technique

Clathrin-coated vesicles transport selective integral membrane proteins from the plasma membrane to endosomes and from the TGN to endosomes. Recycling of proteins from endosomes to the plasma membrane occurs via unidentified vesicles. To study this pathway, we used a novel technique that allows for the immunoelectron microscopic examination of transferrin receptor-containing endosomes in nonsectioned cells. Endosomes were identified as separate discontinuous tubular-vesicular entities. Each endosome was decorated, mainly on the tubules, with many clathrin-coated buds. Endosome-associated clathrin-coated buds were discerned from plasma membrane-derived clathrin-coated vesicles by three criteria: size (60 nm and 100 nm, respectively), continuity with endosomes, and the lack of labeling for alpha-adaptin. They were also distinguished from TGN-derived clathrin-coated vesicles by their location at the periphery of the cell, size, and the lack of labeling for gamma-adaptin. In the presence of brefeldin A, a large continuous endosomal network was formed. Transferrin receptor recycling as well as the formation of clathrin-coated pits at endosomes was inhibited in the presence of brefeldin A. Together with the localization of transferrin receptors at endosome-associated buds, this indicates that a novel class of clathrin-coated vesicles serves an exit pathway from endosomes. The target organelles for endosome-derived clathrin-coated vesicles remain, however, to be identified.

scholarly journals GLUT4 Retention in Adipocytes Requires Two Intracellular Insulin-regulated Transport Steps

2002 ◽  
Vol 13 (7) ◽  
pp. 2421-2435 ◽  
Author(s):  
Anja Zeigerer ◽  
Michael A. Lampson ◽  
Ola Karylowski ◽  
David D. Sabatini ◽  
Milton Adesnik ◽  
...  
Keyword(s):  
Cell Surface ◽  
Transferrin Receptor ◽  
Glucose Transporter ◽  
Trafficking Pathway ◽  
Endosomal Recycling ◽  
Step Model ◽  
Recycling Pathway ◽  
Endosomal Pathway ◽  
Endosomal System ◽  
Regulated Trafficking

Insulin regulates glucose uptake into fat and muscle by modulating the distribution of the GLUT4 glucose transporter between the surface and interior of cells. The GLUT4 trafficking pathway overlaps with the general endocytic recycling pathway, but the degree and functional significance of the overlap are not known. In this study of intact adipocytes, we demonstrate, by using a compartment-specific fluorescence-quenching assay, that GLUT4 is equally distributed between two intracellular pools: the transferrin receptor-containing endosomes and a specialized compartment that excludes the transferrin receptor. These pools of GLUT4 are in dynamic communication with one another and with the cell surface. Insulin-induced redistribution of GLUT4 to the surface requires mobilization of both pools. These data establish a role for the general endosomal system in the specialized, insulin-regulated trafficking of GLUT4. Trafficking through the general endosomal system is regulated by rab11. Herein, we show that rab11 is required for the transport of GLUT4 from endosomes to the specialized compartment and for the insulin-induced translocation to the cell surface, emphasizing the importance of the general endosomal pathway in the specialized trafficking of GLUT4. Based on these findings we propose a two-step model for GLUT4 trafficking in which the general endosomal recycling compartment plays a specialized role in the insulin-regulated traffic of GLUT4. This compartment-based model provides the framework for understanding insulin-regulated trafficking at a molecular level.

Effect of proteases on activation of resting chick embryo fibroblasts and on cell surface proteins

Cell ◽  
1975 ◽  
Vol 6 (2) ◽  
pp. 137-147 ◽  
Author(s):  
Peter M. Blumberg ◽  
Phillips W. Robbins
Keyword(s):  
Chick Embryo ◽  
Cell Surface ◽  
Surface Proteins ◽  
Cell Surface Proteins ◽  
Embryo Fibroblasts

scholarly journals Genetic dissection of early endosomal recycling highlights a TORC1-independent role for Rag GTPases

2017 ◽  
Vol 216 (10) ◽  
pp. 3275-3290 ◽  
Author(s):  
Chris MacDonald ◽  
Robert C. Piper
Keyword(s):  
Plasma Membrane ◽  
Cell Surface ◽  
Surface Membrane ◽  
Physiological Role ◽  
Amino Acid Transporters ◽  
Genetic Dissection ◽  
Cellular Processes ◽  
Rag Gtpases ◽  
Endosomal Recycling ◽  
Recycling Pathway

Endocytosed cell surface membrane proteins rely on recycling pathways for their return to the plasma membrane. Although endosome-to-plasma membrane recycling is critical for many cellular processes, much of the required machinery is unknown. We discovered that yeast has a recycling route from endosomes to the cell surface that functions efficiently after inactivation of the sec7-1 allele of Sec7, which controls transit through the Golgi. A genetic screen based on an engineered synthetic reporter that exclusively follows this pathway revealed that recycling was subject to metabolic control through the Rag GTPases Gtr1 and Gtr2, which work downstream of the exchange factor Vam6. Gtr1 and Gtr2 control the recycling pathway independently of TORC1 regulation through the Gtr1 interactor Ltv1. We further show that the early-endosome recycling route and its control though the Vam6>Gtr1/Gtr2>Ltv1 pathway plays a physiological role in regulating the abundance of amino acid transporters at the cell surface.

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