Synthesis, post-translational processing, and autocrine transforming activity of a carboxylterminal truncated form of colony stimulating factor-1.
The mononuclear phagocyte colony stimulating factor encoded by a 1.6 kilobase pair human cDNA is synthesized as a homodimeric transmembrane glycoprotein that is released from the plasma membrane by proteolysis. Premature termination of the CSF-1 coding sequence upstream of its carboxylterminal transmembrane-spanning segment and expression of the truncated CSF-1 cDNA in either bovine papilloma virus or retrovirus vectors led to the synthesis of a soluble, biologically active growth factor that was rapidly secreted from cells. Like the full-length CSF-1 precursor, the truncated polypeptide was rapidly assembled through disulfide bonds immediately after synthesis and acquired asparagine-linked oligosaccharide chains that underwent progressive post-translational modifications during intracellular transport. Soluble CSF-1 encoded by the truncated cDNA stimulated the formation of bone marrow-derived mouse macrophage colonies in semisolid medium and induced transformation of mouse NIH-3T3 cells when coexpressed with the human c-fms proto-oncogene product (CSF-1 receptor). Compared to results obtained with the full-length CSF-1 cDNA, the efficiency of transformation obtained with the truncated CSF-1 gene was reduced, in spite of the fact that transfected cultures produced similar levels of the extracellular growth factor. The results indicate that CSF-1 amino acid residues 1-158 (together with the aminoterminal signal peptide at residues -32 to -1) are sufficient for biological activity and that CSF-1 cDNAs encoding either membrane-bound or soluble precursors are active in autocrine transformation.
Heard
J M
JM
Department of Tumor Cell Biology, St. Jude Children's Research Hospital, Memphis, TN 38105.
Roussel
M F
MF
Rettenmier
C W
CW
Sherr
C J
CJ
D000818:Animals; D002471:Cell Transformation, Neoplastic; D003001:Cloning, Molecular; D003115:Colony-Stimulating Factors / Q000378:metabolism* / Q000494:pharmacology; D005822:Genetic Vectors; D006031:Glycosylation; D006801:Humans; D066298:In Vitro Techniques; D008562:Membrane Glycoproteins / Q000378:metabolism; D051379:Mice; D011499:Protein Processing, Post-Translational; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000502:physiology; D016186:Receptor, Macrophage Colony-Stimulating Factor; D012995:Solubility; D013329:Structure-Activity Relationship
D003115:Colony-Stimulating Factors; C000715470:MAS1 protein, human; D008562:Membrane Glycoproteins; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D016186:Receptor, Macrophage Colony-Stimulating Factor