title: Calcium modulation of monoclonal antibody binding to phosphatidylinositol phosphate.
abstract: The binding characteristics of two monoclonal antibodies (mAb) to phosphatidylinositol-4-phosphate (PIP) were examined: a murine IgM mAb to PIP; and a human IgG mAb (4E10) that binds both to HIV-1 envelope protein and also to neutral and anionic phospholipids, including PIP. Binding of each mAb to pure PIP was inhibited by Ca(2+) as determined by ELISA. When studied by surface plasmon resonance, liposomes containing PIP could be stripped (i.e., removed) by either Ca(2+) or phosphorylated haptens after binding of the liposomes to the murine anti-PIP antibody attached to a BIAcore chip. In contrast, the binding of liposomal PIP to 4E10 was irreversible and could not be stripped. We therefore conclude that Ca(2+) and phosphate can modulate the initial binding of both types of antibodies to PIP. However, 4E10 binds to liposomal PIP in a two-stage process involving first Ca(2+)-modulated binding to the PIP polar headgroup, followed by irreversible binding to liposomal hydrophobic groups.
authors.affiliation: Henry M. Jackson Foundation for Military Medical Research, USA.
authors.forename: Zoltan
authors.initials: Z
authors.lastname: Beck
authors.forename: Nicos
authors.initials: N
authors.lastname: Karasavvas
authors.forename: James
authors.initials: J
authors.lastname: Tong
authors.forename: Gary R
authors.initials: GR
authors.lastname: Matyas
authors.forename: Mangala
authors.initials: M
authors.lastname: Rao
authors.forename: Carl R
authors.initials: CR
authors.lastname: Alving
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D001665:Binding Sites; D002118:Calcium / Q000494:pharmacology*; D002413:Cations, Divalent; D004305:Dose-Response Relationship, Drug; D004492:Edetic Acid / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D015497:HIV-1 / Q000276:immunology / Q000378:metabolism; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D007075:Immunoglobulin M / Q000276:immunology / Q000378:metabolism*; D008081:Liposomes / Q000276:immunology / Q000378:metabolism; D051379:Mice; D018129:Phosphatidylinositol Phosphates / Q000276:immunology / Q000378:metabolism*; D010743:Phospholipids / Q000276:immunology / Q000378:metabolism; D014759:Viral Envelope Proteins / Q000276:immunology / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D002413:Cations, Divalent; D007075:Immunoglobulin M; D008081:Liposomes; D018129:Phosphatidylinositol Phosphates; D010743:Phospholipids; D014759:Viral Envelope Proteins; C037178:phosphatidylinositol 4-phosphate; D004492:Edetic Acid; D002118:Calcium