Expression and functionality of the trkA proto-oncogene product/NGF receptor in undifferentiated hematopoietic cells.
The expression of the low-affinity NGF receptor (p75) and the trkA proto-oncogene product was analyzed in a series of human hematopoietic cell lines at protein and RNA levels. We did not detect any form of NGF receptor in cell lines displaying a myelomonocytic phenotype (HL60 and U937). In contrast, cells displaying a more immature erythroleukemic phenotype (TF1 and K562) expressed TrkA in the absence of detectable p75. Scatchard analysis showed a single high-affinity site for NGF (kd = 10(-10) mol/L), with a copy number ranging from 300 to 3,000 sites per cell depending on the studied cell line. In addition, NGF induced autophosphorylation of TrkA and could substitute for granulocyte-monocyte colony-stimulating factor to trigger the proliferation of the TF1 cell line, with a half-maximal signal observed at 50 pmol/L, indicating that p75 is not required for DNA synthesis in this cell line. The physiologic relevance of NGF in early hematopoiesis was confirmed by showing that 12% to 15% of progenitor blood cells from mice treated with 5-fluorouracil expressed TrkA and that these cells could be induced to proliferate and differentiate in response to NGF in association with macrophage colony-stimulating factor. Our study demonstrates for the first time that trkA proto-oncogene expression and activation is not restricted to the nervous system, but is also an important element in early hematopoiesis.
Chevalier
S
S
Neurobiologie et immunopathologie des maladies du système nerveux, INSERM U298, CHRU Angers, France.
Praloran
V
V
Smith
C
C
MacGrogan
D
D
Ip
N Y
NY
Yancopoulos
G D
GD
Brachet
P
P
Pouplard
A
A
Gascan
H
H
D000818:Animals; D002460:Cell Line; D006410:Hematopoiesis; D006801:Humans; D004915:Leukemia, Erythroblastic, Acute / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D009414:Nerve Growth Factors / Q000378:metabolism / Q000494:pharmacology; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000032:analysis* / Q000235:genetics / Q000502:physiology; D012333:RNA, Messenger / Q000032:analysis; D020794:Receptor Protein-Tyrosine Kinases / Q000032:analysis* / Q000235:genetics / Q000502:physiology; D020917:Receptor, trkA; D017475:Receptors, Nerve Growth Factor / Q000032:analysis* / Q000235:genetics / Q000502:physiology
C000715470:MAS1 protein, human; D009414:Nerve Growth Factors; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D017475:Receptors, Nerve Growth Factor; D020794:Receptor Protein-Tyrosine Kinases; D020917:Receptor, trkA