The glycosyl-phosphatidylinositol (GPI)-anchored glycoprotein Thy-1 is one of the most abundant molecules expressed on the surface of rat mast cells and rat basophilic leukemia (RBL) cells. The finding that Thy-1 from detergent-solubilized RBL-2H3 cells forms complexes with src-related protein-tyrosine kinase p56/p53lyn suggested that this kinase may play a key role in Thy-1-mediated mast-cell activation. The molecular mechanism of this activation is, however, unknown. Here we show that in RBL-2H3-derived cells extracted by the standard procedure with several non-ionic detergents, the majority of Thy-1 and p56/p53lyn were not released into postnuclear supernatant but remained associated with the detergent-resistant cytoskeletal/nuclear fraction. Pretreatment of the cells with the cholesterol-complexing agents, saponin or digitonin, resulted in complete solubilization of Thy-1 and p56/p53lyn in non-ionic detergents and dissociation of the complexes; this implies that cholesterol plays a crucial role in stabilization of the complexes. This conclusion was supported by double immunofluorescence colocalization experiments which also allowed us to estimate the size of the insoluble complexes to be about 0.1 micron. Sequential treatment with saponin and Nonidet P-40 was used to fractionate tyrosine-phosphorylated proteins during Thy-1-mediated activation of RBL-2H3 cells. Among the soluble cytoplasmic proteins the most dramatic change in tyrosine phosphorylation was found in pp72, whereas pp40 and pp33 were found mainly in the membrane fraction. Our data suggest that surface aggregation of GPI-anchored Thy-1 molecules leads to aggregation of p56/p53lyn kinase located in the same membrane microdomain, followed by transphosphorylation of both soluble and membrane-bound substrates.

• MeSH
• antigeny Thy-1 imunologie   MeSH
• buněčná membrána imunologie   MeSH
• cholesterol fyziologie   MeSH
• detergenty MeSH
• elektroforéza v polyakrylamidovém gelu MeSH
• fluorescenční protilátková technika MeSH
• krysa rodu Rattus MeSH
• lidé MeSH
• mastocyty imunologie   MeSH
• molekulární sekvence - údaje MeSH
• myši MeSH
• precipitinové testy MeSH
• sekvence nukleotidů MeSH
• skupina kinas odvozených od src-genu metabolismus   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• lidé MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• antigeny Thy-1 MeSH
• cholesterol MeSH
• detergenty MeSH
• lyn protein-tyrosine kinase MeSH Prohlížeč
• skupina kinas odvozených od src-genu MeSH

The T-lymphocyte co-receptors of MHC glycoproteins CD4 and CD8 are known to be associated with the protein tyrosine kinase Lck via cysteine-containing sequences in the cytoplasmic domains of CD4 and CD8 and in the N-terminal domain of Lck. Here we demonstrate that a fraction of CD4 and CD8 molecules are associated with very large, detergent-resistant complexes containing several glycosylphosphatidylinositol-anchored proteins, (glyco)lipids, and protein tyrosine kinases Lck and Fyn but apparently no other major transmembrane proteins. Association of Lck and Fyn with these large complexes is, in contrast to simple CD4/CD8-Lck complexes, not sensitive to alkylation with iodoacetamide. These large complexes therefore represent an alternative way of association of CD4 and CD8 with the protein tyrosine kinases, which may play a role in signaling through these receptors.

• MeSH
• antigeny CD4 analýza   MeSH
• antigeny CD8 analýza   MeSH
• buněčná membrána chemie   MeSH
• glykosylfosfatidylinositoly MeSH
• lidé MeSH
• lymfocyty chemie   MeSH
• nádorové proteiny * MeSH
• tyrosinkinasa p56(lck), specifická pro lymfocyty MeSH
• tyrosinkinasy analýza   klasifikace   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• antigeny CD4 MeSH
• antigeny CD8 MeSH
• FRK protein, human MeSH Prohlížeč
• glykosylfosfatidylinositoly MeSH
• nádorové proteiny * MeSH
• tyrosinkinasa p56(lck), specifická pro lymfocyty MeSH
• tyrosinkinasy MeSH