title: Granulocyte-macrophage colony-stimulating factor increases synthesis and expression of CR1 and CR3 by human peripheral blood neutrophils.
abstract: Polymorphonuclear leukocytes (PMN) constitutively synthesize various plasma membrane proteins including CR1(3) (CD35), CR3 (or Mac-1) alpha-chain (CD11b) and MHC class I. PMN are also able to up-regulate rapidly the expression of CR1 and CR3 to the plasma membrane in response to agonists such as FMLP. To determine whether constitutive PMN translation was static or up-regulatable, PMN were cultured in the presence or absence of the cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF) for 8 h. CR1, CR3 and class I proteins immunoprecipitated from lysates of 35S-methionine pulse-labeled PMN were resolved by SDS-PAGE, fluorographed and quantified by densitometry. GM-CSF-treated PMN synthesized 4.5-fold more class I protein, 3.7-fold more CR1, 2.4-fold more CD11b and 3.4-fold more CR3 beta-chain (CD18), compared with untreated control cells. Actinomycin D treatment of replicate samples of PMN decreased the amount of these proteins synthesized by each group of PMN from 30 to 90%, implying that continued translation was required for the increases in protein synthesis. Nascent CR and class I proteins were inserted into the plasma membrane of PMN, thereby supplementing the molecules already expressed on the cell surface. In addition to these longer term effects of GM-CSF, we observed its acute up-regulatory effects on PMN. GM-CSF induced a five- to 12-fold increase in the expression of CR1 and CR3 on the PMN cell surface within 30 min. These increases were both dose- and time-dependent with maximum up-regulation occurring at 25 pM and at 30 min. In contrast to the long term biosynthetic events, this rapid up-regulation was not dependent on protein synthesis but was due instead to mobilization of CR from intracellular compartments similar to those up-regulated by FMLP. These results demonstrate that PMN can respond to microenvironmental stimuli such as GM-CSF both by rapidly up-regulating and increasing translation and expression of functionally important plasma membrane proteins.
authors.affiliation: Department of Medicine, Harvard Medical School, Boston, MA.
authors.forename: E
authors.initials: E
authors.lastname: Neuman
authors.forename: J W
authors.initials: JW
authors.lastname: Huleatt
authors.forename: R M
authors.initials: RM
authors.lastname: Jack
mesh_terms: D018821:CD18 Antigens; D002462:Cell Membrane / Q000378:metabolism; D003609:Dactinomycin / Q000494:pharmacology; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology*; D015395:Histocompatibility Antigens Class I / Q000096:biosynthesis / Q000276:immunology; D006801:Humans; D016177:Macrophage-1 Antigen / Q000032:analysis / Q000096:biosynthesis* / Q000276:immunology; D008565:Membrane Proteins / Q000096:biosynthesis; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism*; D011951:Receptors, Complement / Q000096:biosynthesis* / Q000276:immunology; D017463:Receptors, Complement 3b; D016028:Receptors, Leukocyte-Adhesion / Q000032:analysis
chemical_list: D018821:CD18 Antigens; D015395:Histocompatibility Antigens Class I; D016177:Macrophage-1 Antigen; D008565:Membrane Proteins; D011951:Receptors, Complement; D017463:Receptors, Complement 3b; D016028:Receptors, Leukocyte-Adhesion; D003609:Dactinomycin; D009240:N-Formylmethionine Leucyl-Phenylalanine; D016178:Granulocyte-Macrophage Colony-Stimulating Factor