ALTERNATIVE FORMS OF RAT TRKC WITH DIFFERENT FUNCTIONAL CAPABILITIES

We have identified transcripts encoding several different forms of rat TrkC, a member of the Trk family of receptor tyrosine kinases that se rves as a receptor for neurotrophin-3. Some forms of TrkC lack the int racytoplasmic kinase domain and thus resemble previously defined trunc ated variants of TrkB. Other forms of TrkC contain variable-sized amin o acid insertions within the tyrosine kinase domain. Transcripts encod ing all forms of TrkC can be detected throughout the nervous system, d isplaying substantial overlap as well as mutually exclusive distributi on patterns with transcripts for TrkB. Strikingly, only transcripts en coding the truncated forms of TrkB and TrkC are found in astrocytes, p eripheral nerve, and nonneural tissues. Finally, forms of TrkC contain ing insertions within the kinase domain retain their ability to autoph osphorylate in response to neurotrophin-3, but cannot mediate prolifer ation in fibroblasts or neuronal differentiation in PC12 cells.