Topography of plasma membrane microdomains and its consequences for mast cell signaling.
Thy-1 (CD90) is a glycoprotein bound to the plasma membrane by a GPI anchor. Aggregation of Thy-1 in mast cells and basophils induces activation events independent of the expression of Fcepsilon receptor I (FcepsilonRI). Although we and others have previously suggested that plasma membrane microdomains called lipid rafts are implicated in both Thy-1 and FcepsilonRI signaling, properties of these microdomains are still poorly understood. In this study we used rat basophilic leukemia cells and their transfectants expressing both endogenous Thy-1.1 and exogenous Thy-1.2 genes and analyzed topography of the Thy-1 isoforms and Thy-1-induced signaling events. Light microscopy showed that both Thy-1 isoforms were in the plasma membrane distributed randomly and independently. Electron microscopy on isolated membrane sheets and fluorescence resonance energy transfer analysis indicated cross-talk between Thy-1 isoforms and between Thy-1 and FcepsilonRI. This cross-talk was dependent on actin filaments. Thy-1 aggregates colocalized with two transmembrane adaptor proteins, non-T cell activation linker (NTAL) and linker for activation of T cells (LAT), which had been shown to inhabit different membrane microdomains. Thy-1 aggregation led to tyrosine phosphorylation of these two adaptors. The combined data indicate that aggregated GPI-anchored proteins can attract different membrane proteins in different clusters and thus can trigger different signaling pathways.
Heneberg
Petr
P
Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
Lebduska
Pavel
P
Dráberová
L'ubica
L
Korb
Jan
J
Dráber
Petr
P
D000199:Actins / Q000378:metabolism; D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000818:Animals; D031541:Fluorescence Resonance Energy Transfer; D015151:Immunoblotting; D008407:Mast Cells / Q000276:immunology / Q000378:metabolism* / Q000648:ultrastructure*; D021962:Membrane Microdomains / Q000648:ultrastructure*; D008565:Membrane Proteins / Q000378:metabolism; D016253:Microscopy, Immunoelectron; D010750:Phosphoproteins / Q000378:metabolism; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D051381:Rats; D020239:Receptor Cross-Talk; D017455:Receptors, IgE / Q000276:immunology / Q000378:metabolism; D015398:Signal Transduction / Q000276:immunology*; D018800:Thy-1 Antigens / Q000235:genetics / Q000378:metabolism*; D014162:Transfection
D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; C491734:Lat protein, mouse; D008565:Membrane Proteins; D010750:Phosphoproteins; D020033:Protein Isoforms; D017455:Receptors, IgE; D018800:Thy-1 Antigens