PROTEIN-TYROSINE PHOSPHORYLATION - IMPLICATIONS FOR SYNAPTIC FUNCTION

The phosphorylation of proteins on tyrosine residues, initially believ ed to be primarily involved in cell growth and differentiation, is now recognized as having a critical role in regulating the function of ma ture cells. The brain exhibits one of the highest levels of tyrosine k inase activity in the adult animal and the synaptic region is particul arly rich in tyrosine kinases and tyrosine phosphorylated proteins. Re cent studies have described the effects of tyrosine phosphorylation on the activities of a number of proteins which are potentially involved in the regulation of synaptic function. Furthermore, it is becoming a pparent that tyrosine phosphorylation is involved in the modification of synaptic activity, such as occurs during depolarization, the induct ion of long-term potentiation or long-term depression, and ischemia. C hanges in the activities of tyrosine kinases and/or protein tyrosine p hosphatases which are associated with synaptic structures may result i n altered tyrosine phosphorylation of proteins located at the synapse leading to both short-term and long-lasting changes in synaptic and ne uronal function. (C) 1997 Elsevier Science Ltd.