Activated FcgammaRII and signalling molecules revealed in rafts by ultra-structural observations of plasma-membrane sheets.
To reveal topography of FcgammaRII components of the receptor-signalling complex, large plasma-membrane sheets were obtained by cell cleavage and analysed by immuno-electron microscopy. Non-activated FcgammaRII was dispersed in the plane of the plasma membrane and only rarely was localized in the proximity of Lyn, an Src family tyrosine kinase, and CD55, a glycosylphosphatidylinositol-anchored protein. After FcgammaRII activation by cross-linking with antibodies, clusters of an electron-dense material acquiring about 86% of FcgammaRII and reaching up to 300 nm in diameter were formed within 5 min. These structures also accommodated about 85% of Lyn and 63% of CD55 labels that were located in close vicinity of gold particles attributed to the cross-linked FcgammaRII . The electron-dense structures were also abundant in tyrosine phosphorylated proteins. At their margins PIP2 was preferentially located. Based on a concentration of Lyn, CD55 and activated FcgammaRII , the electron-dense structures seem to reflect coalescent membrane rafts.
Strzelecka-Kiliszek
Agnieszka
A
Department of Cell Biology, Nencki Institute of Experimental Biology, Warsaw, Poland.
Korzeniowski
Marek
M
Kwiatkowska
Katarzyna
K
Mrozińska
Kazimiera
K
Sobota
Andrzej
A
D000911:Antibodies, Monoclonal; D015703:Antigens, CD / Q000378:metabolism* / Q000648:ultrastructure; D018958:CD55 Antigens / Q000378:metabolism* / Q000648:ultrastructure; D002460:Cell Line; D006801:Humans; D021962:Membrane Microdomains / Q000378:metabolism* / Q000648:ultrastructure; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000737:chemistry / Q000378:metabolism; D017452:Receptors, IgG / Q000378:metabolism* / Q000648:ultrastructure; D019061:src-Family Kinases / Q000378:metabolism* / Q000648:ultrastructure
D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D018958:CD55 Antigens; C080568:Fc gamma receptor IIA; D019269:Phosphatidylinositol 4,5-Diphosphate; D017452:Receptors, IgG; C060902:lyn protein-tyrosine kinase; D019061:src-Family Kinases