THE ASSOCIATION OF THE PROTEIN-TYROSINE KINASES P56(LCK) AND P60(FYN)WITH THE GLYCOSYL PHOSPHATIDYLINOSITOL-ANCHORED PROTEINS THY-1 AND CD48 IN RAT THYMOCYTES IS DEPENDENT ON THE STATE OF CELLULAR ACTIVATION
D. Garnett et al., THE ASSOCIATION OF THE PROTEIN-TYROSINE KINASES P56(LCK) AND P60(FYN)WITH THE GLYCOSYL PHOSPHATIDYLINOSITOL-ANCHORED PROTEINS THY-1 AND CD48 IN RAT THYMOCYTES IS DEPENDENT ON THE STATE OF CELLULAR ACTIVATION, European Journal of Immunology, 23(10), 1993, pp. 2540-2544
Cell surface glycoproteins anchored to the plasma membrane via glycosy
lphosphatidylinositol (GPI) structures, and hence having no cytoplasmi
c domains, can nevertheless transmit activation signals in lymphocytes
. By immunoprecipitation from detergent lysates and in vitro immune co
mplex kinase reactions the GPI-anchored molecules Thy-1 and CD48 are s
hown to be associated with multimolecular complexes of phosphoproteins
including the protein tyrosine kinases p56lck and p60fyn in both rat
and mouse thymocytes. Moreover, the kinase activity associated with Th
y-1 on rat thymocytes is shown to be dependent on the activation state
of the cells, with stimulation by the lectin, concanavalin A, produci
ng a marked decrease in Thy-1-associated kinase activity. In such acti
vated cells, there is an increased association of kinase activity with
CD48, but this may be explained in terms of increased surface express
ion of CD48 and of increased total kinase activity. Additional phospho
proteins of 85, 36 and 32 kDa were consistently seen as components of
the complexes.