Abnormal response to granulocyte colony-stimulating factor (G-CSF) in canine cyclic hematopoiesis is not caused by altered G-CSF receptor expression.
A decrease in responsiveness to granulocyte colony-stimulating factor (G-CSF) has been implicated in the pathophysiology of cyclic hematopoiesis. Using the canine model of cyclic neutropenia, we examined the response of neutrophil precursors to G-CSF in vitro and G-CSF receptor expression in neutrophils from grey collie dogs to determine whether the abnormal response observed to G-CSF in vivo in this disorder is present at the level of the progenitor cell and is caused by defective G-CSF receptor expression. Bone marrow mononuclear cells from grey collie dogs required sevenfold higher G-CSF concentrations than normal dog cells to achieve half-maximal colony growth [56 pmol/L v 8 pmol/L). Receptor binding assays with 125I-labeled G-CSF and Scatchard analyses of the equilibrium binding data were consistent with expression of a single class of high-affinity receptors for G-CSF on neutrophils from both normal dogs and grey collies with similar receptor numbers (56 to 446 sites/cell v 78 to 199 sites/cell) and binding affinities (28 to 206 pmol/L v 84 to 195 pmol/L). Chemical cross-linking studies identified a G-CSF binding protein of approximately 120 kD on neutrophils from grey collies, similar in size to that on normal dog neutrophils. No abnormal G-CSF receptor mRNA transcripts were detected in neutrophils from grey collie dogs by Northern blot analysis. Treatment of both normal and grey collie neutrophils with G-CSF rapidly induced tyrosine phosphorylation of an 80-kD protein that behaved like canine c-rel. These results demonstrate that the abnormal responsiveness to G-CSF in canine cyclic hematopoiesis is present in neutrophil precursors and is not associated with demonstrable alterations in the number, binding affinity, or overall size of the G-CSF receptor in neutrophils, or with defective tyrosine phosphorylation of p80. These data suggest that cyclic hematopoiesis is caused by a defect in the G-CSF signal transduction pathway at a point distal to G-CSF receptor binding that does not involve the early biochemical events leading to p80 tyrosine phosphorylation.
Avalos
B R
BR
Department of Internal Medicine, Ohio State University, Columbus 43210.
Broudy
V C
VC
Ceselski
S K
SK
Druker
B J
BJ
Griffin
J D
JD
Hammond
W P
WP
D000818:Animals; D001854:Bone Marrow Cells; D004283:Dog Diseases / Q000378:metabolism*; D004285:Dogs; D015870:Gene Expression; D016179:Granulocyte Colony-Stimulating Factor / Q000378:metabolism*; D006410:Hematopoiesis; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000378:metabolism; D010507:Periodicity; D019000:Phosphotyrosine; D012333:RNA, Messenger / Q000235:genetics; D016188:Receptors, Granulocyte Colony-Stimulating Factor / Q000378:metabolism*; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism
D012333:RNA, Messenger; D016188:Receptors, Granulocyte Colony-Stimulating Factor; D016179:Granulocyte Colony-Stimulating Factor; D019000:Phosphotyrosine; D014443:Tyrosine