Cell surface receptors for ecotropic murine retroviruses: Mobile membrane proteins that mediate binding and slow endocytosis of the viral envelope glycoprotein

David Kabat

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

The gp70 envelope glycoproteins of ecotropic murine leukemia viruses bind to receptors that occur only on mouse and rat cells and on interspecies hybrid cells that contain mouse chromosome 5. A substantial fraction of the gp70 that was bound specifically by these criteria remained undegraded and accessible to extracellular labeling reagents for many hours. Accordingly, cells with ecotropic receptors could be labeled specifically. As seen by immunofluorescence microscopy, the gp70-receptor complexes were uniformly dispersed on mouse fibroblast plasma membranes. These complexes were mobile, and they aggregated into patches when crosslinked by antibodies at 37°, but not when membrane lipid fluidity was frozen at 0°. Ecotropic receptors still bound gp70 specifically after cells were fixed with 3.7% formaldehyde, but these receptors could not be patched, indicating that they were nondiffusible. Viable cells slowly endocytosed gp70-receptor complexes at 37° (approximate half-life 5-7 hr) and the gp70 was then proteolytically degraded in lysosomes. In the presence of 20 μM chloroquine, a lysosomal inhibitor, undegraded gp70 was seen to slowly accumulate in these intracellular organelles. These results suggest that ecotropic receptors mediate a slow internalization of attached ligand. Long-lived binding of gp70 onto surfaces of uninfected cells may explain important features of viral-induced leukemia, the host immune response, and immunosuppression.

Original languageEnglish (US)
Pages (from-to)467-474
Number of pages8
JournalVirology
Volume171
Issue number2
DOIs
StatePublished - 1989

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Cell Surface Receptors
Retroviridae
Endocytosis
Protein Binding
Glycoproteins
Membrane Proteins
Murine Leukemia Viruses
Chromosomes, Human, Pair 5
Membrane Fluidity
Hybrid Cells
Chloroquine
Membrane Lipids
Lysosomes
Fluorescence Microscopy
Organelles
Immunosuppression
Formaldehyde
Half-Life
Leukemia
Fibroblasts

ASJC Scopus subject areas

  • Virology
  • Infectious Diseases

Cite this

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abstract = "The gp70 envelope glycoproteins of ecotropic murine leukemia viruses bind to receptors that occur only on mouse and rat cells and on interspecies hybrid cells that contain mouse chromosome 5. A substantial fraction of the gp70 that was bound specifically by these criteria remained undegraded and accessible to extracellular labeling reagents for many hours. Accordingly, cells with ecotropic receptors could be labeled specifically. As seen by immunofluorescence microscopy, the gp70-receptor complexes were uniformly dispersed on mouse fibroblast plasma membranes. These complexes were mobile, and they aggregated into patches when crosslinked by antibodies at 37°, but not when membrane lipid fluidity was frozen at 0°. Ecotropic receptors still bound gp70 specifically after cells were fixed with 3.7{\%} formaldehyde, but these receptors could not be patched, indicating that they were nondiffusible. Viable cells slowly endocytosed gp70-receptor complexes at 37° (approximate half-life 5-7 hr) and the gp70 was then proteolytically degraded in lysosomes. In the presence of 20 μM chloroquine, a lysosomal inhibitor, undegraded gp70 was seen to slowly accumulate in these intracellular organelles. These results suggest that ecotropic receptors mediate a slow internalization of attached ligand. Long-lived binding of gp70 onto surfaces of uninfected cells may explain important features of viral-induced leukemia, the host immune response, and immunosuppression.",
author = "David Kabat",
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AB - The gp70 envelope glycoproteins of ecotropic murine leukemia viruses bind to receptors that occur only on mouse and rat cells and on interspecies hybrid cells that contain mouse chromosome 5. A substantial fraction of the gp70 that was bound specifically by these criteria remained undegraded and accessible to extracellular labeling reagents for many hours. Accordingly, cells with ecotropic receptors could be labeled specifically. As seen by immunofluorescence microscopy, the gp70-receptor complexes were uniformly dispersed on mouse fibroblast plasma membranes. These complexes were mobile, and they aggregated into patches when crosslinked by antibodies at 37°, but not when membrane lipid fluidity was frozen at 0°. Ecotropic receptors still bound gp70 specifically after cells were fixed with 3.7% formaldehyde, but these receptors could not be patched, indicating that they were nondiffusible. Viable cells slowly endocytosed gp70-receptor complexes at 37° (approximate half-life 5-7 hr) and the gp70 was then proteolytically degraded in lysosomes. In the presence of 20 μM chloroquine, a lysosomal inhibitor, undegraded gp70 was seen to slowly accumulate in these intracellular organelles. These results suggest that ecotropic receptors mediate a slow internalization of attached ligand. Long-lived binding of gp70 onto surfaces of uninfected cells may explain important features of viral-induced leukemia, the host immune response, and immunosuppression.

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