title: Involvement of the pertussis toxin-sensitive GTP-binding protein in regulation of expression and function of granulocyte complement receptor type 1 and type 3.
abstract: Human polymorphonuclear leukocytes (PMN) express receptors for complement (C) C3b and C3bi termed CR1 and CR3, respectively. The addition of PMA or fMLP to PMN enhances the capacity of these receptors to promote binding of C3b- and C3bi-coated erythrocytes. fMLP-dependent increase of the binding of these ligand-coated erythrocytes was completely abolished by prior exposure of the PMN to pertussis toxin (IAP). GTP-binding protein (Gi alpha) was ADP-ribosylated and dysfunctional by this treatment. On the other hand, PMA-dependent binding of these ligands, as well as control binding, was inhibited only slightly, if at all, by the IAP treatment. The levels of C receptor expression on cell surface were determined by flow cytometry using monoclonal antibody against CR1 and those against the alpha and beta chains of CR3 (CR3 is composed of alpha and beta chain). Upon exposure of PMN to the chemotactic factor or PMA, or upon incubation of the cells at 37 degrees C, the surface expression of CR1 and CR3 alpha was increased. IAP also blocked an fMLP-induced increase of CR1 and CR3 alpha, but did not block the temperature- or PMA-dependent increase of these receptors. Opsonized zymosan (SOZ), another ligand for CR3, also led to an increase of both CR1 and CR3 alpha. Neither PMA nor SOZ brought about an increase of the surface expression of CR3 beta, but fMLP caused a slight increase of CR3 beta in an IAP-sensitive manner. Based on the IAP-sensitivity of the receptor expression, therefore, it appears that at least two separate mechanisms are operative in the control of C receptors. In addition, the alpha and beta chains of CR3 are regulated independently. The present data offer evidence suggesting that C receptor functions are in part regulated through a GTP-binding protein via modulation of their surface expression.
authors.affiliation: Ui Laboratory, Institute of Physical and Chemical Research, Wako-shi, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Hazeki
authors.forename: T
authors.initials: T
authors.lastname: Seya
authors.forename: O
authors.initials: O
authors.lastname: Hazeki
authors.forename: M
authors.initials: M
authors.lastname: Ui
mesh_terms: D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000502:physiology*; D006098:Granulocytes / Q000166:cytology / Q000502:physiology*; D006801:Humans; D066298:In Vitro Techniques; D016177:Macrophage-1 Antigen / Q000502:physiology*; D037342:Pertussis Toxin; D017463:Receptors, Complement 3b / Q000502:physiology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D015854:Up-Regulation; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
chemical_list: D016177:Macrophage-1 Antigen; D017463:Receptors, Complement 3b; D010566:Virulence Factors, Bordetella; D000246:Adenosine Diphosphate Ribose; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D013755:Tetradecanoylphorbol Acetate