Divergent pathways in COS-7 cells mediate defective internalization and intracellular routing of truncated G-CSFR forms in SCN/AML.
BACKGROUND
Expression of truncated G-CSFR forms in patients with SCN/AML induces hyperproliferation and prolonged cell survival. Previously, we showed that ligand internalization is delayed and degradation of truncated G-CSFR forms is defective in patients with SCN/AML.


RESULTS
In this study, we investigated the potential roles of dileucine and tyrosine-based motifs within the cytoplasmic domain of the G-CSFR in modulating ligand/receptor internalization. Using standard binding assays with radiolabeled ligand and COS-7 cells, substitutions in the dileucine motif or deletion of tyrosine residues in the G-CSFR did not alter internalization. Attachment of the transferrin receptor YTRF internalization motif to a truncated G-CSFR form from a patient with SCN/AML corrected defective internalization, but not receptor degradation suggesting that receptor internalization and degradation occur independently via distinct domains and/or processes.


CONCLUSIONS
Our data suggest that distinct domains within the G-CSFR mediate separate processes for receptor internalization and degradation. Our findings using standard binding assays differ from recently published data utilizing flow cytometry.
Pulmonary, Allergy, Critical Care and Sleep Medicine, The Ohio State University, Columbus, Ohio, United States of America.
Melissa G
MG
Hunter
Morgan
M
McLemore
Daniel C
DC
Link
Megan
M
Loveland
Alexander
A
Copelan
Belinda R
BR
Avalos
D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D002522:Chlorocebus aethiops; D017931:DNA Primers; D004705:Endocytosis; D015470:Leukemia, Myeloid, Acute / Q000378:metabolism* / Q000473:pathology; D008024:Ligands; D016297:Mutagenesis, Site-Directed; D016188:Receptors, Granulocyte Colony-Stimulating Factor / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism
D017931:DNA Primers; D008024:Ligands; D016188:Receptors, Granulocyte Colony-Stimulating Factor; D014443:Tyrosine