title: Macrophage proliferation is regulated through CSF-1 receptor tyrosines 544, 559, and 807.
abstract: Colony-stimulating factor-1 (CSF-1)-stimulated CSF-1 receptor (CSF-1R) tyrosine phosphorylation initiates survival, proliferation, and differentiation signaling pathways in macrophages. Either activation loop Y807F or juxtamembrane domain (JMD) Y559F mutations severely compromise CSF-1-regulated proliferation and differentiation. YEF, a CSF-1R in which all eight tyrosines phosphorylated in the activated receptor were mutated to phenylalanine, lacks in vitro kinase activity and in vivo CSF-1-regulated tyrosine phosphorylation. The addition of Tyr-807 alone to the YEF backbone (Y807AB) led to CSF-1-independent but receptor kinase-dependent proliferation, without detectable activation loop Tyr-807 phosphorylation. The addition of Tyr-559 alone (Y559AB) supported a low level of CSF-1-independent proliferation that was slightly enhanced by CSF-1, indicating that Tyr-559 has a positive Tyr-807-independent effect. Consistent with the postulated autoinhibitory role of the JMD Tyr-559 and its relief by ligand-induced Tyr-559 phosphorylation, the addition of Tyr-559 to the Y807AB background suppressed proliferation in the absence of CSF-1, but restored most of the CSF-1-stimulated proliferation. Full restoration of kinase activation and proliferation required the additional add back of JMD Tyr-544. Inhibitor experiments indicate that the constitutive proliferation of Y807AB macrophages is mediated by the phosphatidylinositol 3-kinase (PI3K) and ERK1/2 pathways, whereas proliferation of WT and Y559,807AB macrophages is, in addition, contributed to by Src family kinase (SFK)-dependent pathways. Thus Tyr-807 confers sufficient kinase activity for strong CSF-1-independent proliferation, whereas Tyr-559 maintains the receptor in an inactive state. Tyr-559 phosphorylation releases this restraint and may also contribute to the CSF-1-regulated proliferative response by activating Src family kinase.
authors.affiliation: Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
authors.forename: Wenfeng
authors.initials: W
authors.lastname: Yu
authors.forename: Jian
authors.initials: J
authors.lastname: Chen
authors.forename: Ying
authors.initials: Y
authors.lastname: Xiong
authors.forename: Fiona J
authors.initials: FJ
authors.lastname: Pixley
authors.forename: Yee-Guide
authors.initials: YG
authors.lastname: Yeung
authors.forename: E Richard
authors.initials: ER
authors.lastname: Stanley
mesh_terms: D000818:Animals; D049109:Cell Proliferation; D002470:Cell Survival; D003432:Cross-Linking Reagents / Q000494:pharmacology; D005786:Gene Expression Regulation; D006801:Humans; D008264:Macrophages / Q000166:cytology*; D051379:Mice; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D017434:Protein Structure, Tertiary; D016186:Receptor, Macrophage Colony-Stimulating Factor / Q000737:chemistry* / Q000502:physiology*; D015398:Signal Transduction; D013329:Structure-Activity Relationship; D014443:Tyrosine / Q000737:chemistry*
chemical_list: D003432:Cross-Linking Reagents; D014443:Tyrosine; D016186:Receptor, Macrophage Colony-Stimulating Factor