TYROSINE PHOSPHORYLATION AND PROTRUSIVE STRUCTURES OF THE GROWTH CONE

Protein-tyrosine kinase, such as those of the trk and Eph families, se rve as membrane receptors for extracellular cues which regulate the ra te and direction of growth of numerous groups of axons. Certain cytopl asmic protein-tyrosine kinases, such as src, are also abundant in grow th cones. But. how protein-tyrosine phosphorylation regulates the grow th cone is poorly understood. We discuss here potential roles for tyro sine phosphorylation in the protrusive structures of the growth cone, especially filopodia, which are important in detecting cues. A particu lar focus is the integrin receptor for substrate-bound growth promoter s like laminin. Changes in tyrosine phosphorylation may be important i n both facilitating and mediating the interaction of Filopodia with th ese growth promoters.