title: Differential interaction of the C3b/C4b receptor and MHC class I with the cytoskeleton of human neutrophils.
abstract: As measured by fluorescence microscopy and radioligand binding, C3b/C4b receptors (CR1) became attached to the detergent-insoluble cytoskeleton of human neutrophils when receptors were cross-linked by affinity-purified polyclonal F(ab')2 anti-CR1, dimeric C3b, or Fab monoclonal anti-CR1 followed by F(ab')2 goat anti-mouse F(ab')2. CR1 on neutrophils bearing monovalent anti-CR1 was not attached to the cytoskeleton. In contrast, cross-linked CR1 on erythrocytes and cross-linked MHC Class I on neutrophils were not cytoskeleton associated. A possible role for filamentous actin (F-actin) in the binding of cross-linked CR1 to neutrophil cytoskeleton was suggested by three observations. When neutrophils were differentially extracted with either Low Salt-detergent buffer or High Salt-detergent buffer, stained with FITC-phalloidin, and examined by fluorescent flow cytometry, the residual cytoskeletons generated with the former buffer were shown to contain polymerized F-actin, whereas cytoskeletons generated with the latter buffer were found to be depleted of F-actin. In parallel experiments, High Salt-detergent buffer was also found to release cross-linked CR1 from neutrophils. Second, depolymerization of F-actin by DNAse I released half of the cytoskeletal-associated cross-linked CR1. Third, immunoadsorbed neutrophil CR1, but not MHC Class I or erythrocyte CR1, specifically bound soluble 125I-actin. In addition, Fc receptor and CR3, other phagocytic membrane proteins of neutrophils, specifically bound 125I-actin. These data demonstrate that CR1 cross-linked on neutrophils becomes associated with detergent-insoluble cytoskeleton and that this interaction is mediated either directly or indirectly by actin.
mesh_terms: D000199:Actins / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism*; D003169:Complement Inactivator Proteins; D003599:Cytoskeleton / Q000378:metabolism*; D004705:Endocytosis; D006023:Glycoproteins; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000276:immunology; D008285:Major Histocompatibility Complex; D009504:Neutrophils / Q000378:metabolism* / Q000648:ultrastructure; D011951:Receptors, Complement / Q000378:metabolism*; D017463:Receptors, Complement 3b; D011961:Receptors, Fc / Q000378:metabolism
chemical_list: D000199:Actins; D002352:Carrier Proteins; D003169:Complement Inactivator Proteins; D006023:Glycoproteins; D007140:Immunoglobulin Fab Fragments; D011951:Receptors, Complement; D017463:Receptors, Complement 3b; D011961:Receptors, Fc