INTERACTION OF NT-4 AND BDNF WITH GP145(TRKB) RECEPTOR - EFFECT ON CELLULAR-METABOLISM

In the present study a silicon microphysiometer (Cytosensor(R)) was ap plied in investigating interactions of gp145(trkb), a member of the ty rosine kinase receptor family, with different neurotrophic factors. NI H-3T3 cells transfected with gp145(trkb) receptors (NIH3T3/trkB cells) were utilized in the studies. Treatment with brain-derived neurotroph ic factor (BDNF), neurotrophin-4 (NT-4) and neurotrophin-3 (NT-3) indu ced changes in the metabolic rate of NIH3T3/trkB cells. In contrast, n o response was observed with nerve growth factor (NGF). The effects of NT-4 and BDNF on NIH3T3/trkB cells were receptor-specific in that the y did not induce metabolic rate changes in wild type NIH3T3 cells or c ells transfected with either gp140(trka) (TrkA) or gp145(trkc) (TrkC) receptors. Tn contrast, NT-3 induced metabolic rate changes in cells t ransfected with each of the three different Trk receptors. The activit y of NT-4 was significantly higher than that of BDNF. K252a, a protein kinase inhibitor, reduced the NT-4- and BDNF-induced response of the NIH3T3/trkB cells. This suggests that the NT-4 and BDNF-induced metabo lic rate changes are associated with autophosphorylation of the tyrosi ne protein kinase residues. This hypothesis is further supported by re sults of western blot analysis. The results show that interactions of Trk receptors with neurotrophic factors result in metabolic changes in cells expressing the receptors. (C) 1997 Elsevier Science B.V.