SIGNALING EVENTS FOLLOWING THE INTERACTION OF THE NEURONAL ADHESION MOLECULE F3 WITH THE N-TERMINAL DOMAIN OF TENASCIN-R

Interaction between the extracellular matrix protein tenascin-R and th e neuronal adhesion molecule F3 might be involved in the formation of neuronal networks, In this study, the fragment of tenascin-R comprisin g epithelial growth factor (EGF)-like repeats and the cysteine-rich NH 2 terminal stretch (EGF-L), known to be inhibitory for growing neurite s and repellent for growth cones, was used to investigate the signalin g events following the F3/EGF-L interaction, We addressed this questio n using an in vitro test with F3-transfected Chinese hamster ovary (CH O) cells that allowed us to measure the kinetics, magnitude and specif icity of the repellent effect resulting from the specific F3/EGF-L int eraction, We showed that the repellent effect was counteracted by addi tion of the serine/threonine kinase and -phosphatase modulators (staur osporine, okadaic acid and H7) but not by modulators of tyrosine kinas e or -phosphatases, This result indicates that the intracellular signa ls activated bg the repellent effect involve a serine/threonine kinase pathway Furthermore, the repellent effect of the EGF-L fragment for g rowth cones of cultured cerebellar neurons was also abolished by the i dentical modulators of serine/threonine kinase and -phosphatases. The inhibition of neurite outgrowth from hippocampal neurons by EGF-L was abolished in the presence of the serine threonine-kinase inhibitor H7, These results strongly suggest that the F3/tenascin-R interaction thr ough EGF-L involves an intracellular activation of serine/threonine ki nase(s) in all F3-expressing cells tested, (C) 1997 Wiley-Liss, Inc.