THE GLYPIATED NEURONAL CELL-ADHESION MOLECULE CONTACTIN F11 COMPLEXESWITH SRC-FAMILY PROTEIN-TYROSINE KINASE FYN/

Glycosyl phosphatidylinositol-anchored glycoproteins of the immunoglob ulin superfamily play an important role in the formation of neuronal n etworks during development. The mechanism whereby neuronal GPI-linked molecules transduce recognition signals remains to be established. Ana lysis of detergent-resistant immune-complexes reveals that the glypiat ed neuronal cell adhesion molecule contactin/F11 specifically complexe s with the cytoplasmic, nonreceptor type src-family tyrosine kinase Fy n. Antibody-mediated cross-linking of contactin/F11 on embryonic chick neuronal cells leads to an increase of the Fyn-activity coprecipitate d with contactin/F11, and elevates phosphorylation of an additional 75 /80 K component within the contactin/F11-immune-complex. Additionally, binding of ligands, i.e., contactin/F11-specific antibody or tenascin -R, a natural ligand of contactin/F11, to the surface of HeLa transfec tants expressing contactin/F11, causes capping of contactin/F11 and a concomitant change in the distribution of the intracellular kinase Fyn , thus confirming their physical association. This indicates that cont actin/F11-mediated signaling requires Fyn.