Neurotrophin-3 receptors in the developing chicken retina.
Neurotrophin 3 (NT-3) had specific high-affinity receptors (HNT-3R) in the developing chick retina at all ages between embryonic day (E) 4 and E14. The affinity of HNT-3R for 125I-NT-3 did not change with the developmental state. A dissociation constant (kd) of 13 pM was obtained. However, the amount of HNT-3R appeared to be developmentally regulated; the number of receptors/cell increased from E4 up to E6-7 (coinciding with the main onset of neuronal differentiation), then decreased until E9 and increased again by E12, when all retinal cells were differentiated. Kinetic and cross-linking experiments showed that HNT-3R from two prototypical developmental ages, E7 and E14, were different. E7 and E14 HNT-3R could be distinguished from each other on the basis of different inhibition patterns of 125I-NT-3 binding in the presence of nerve growth factor or brain-derived neurotrophic factor. Chemical cross-linking of increasing concentrations of 125I-NT-3 to its receptors showed (a) one 100-kDa band corresponding to neurotrophin low-affinity receptors in both E7 and E14 cells; (b) one 130-kDa band also present in both E7 and E14 cells. Densitometric measurements showed that this 130-kDa band behaved as HNT-3R in E14 cells (kd approximately 10 pM) but not in E7 cells (kd > or = 0.2 nM). Furthermore, the 130-kDa band in both E7 and E14 retinal cells displayed a trk-like immunoreactivity. Our data show that, in neurons, one particular neurotrophin may induce different actions mediated through distinct and specific receptors.
Rodríguez-Tébar
A
A
Instituto Cajal de Neurobiología, CSIC, Madrid, Spain.
de la Rosa
E J
EJ
Arribas
A
A
D000818:Animals; D002454:Cell Differentiation; D002642:Chick Embryo; D003432:Cross-Linking Reagents; D005022:Ethyldimethylaminopropyl Carbodiimide; D007457:Iodine Radioisotopes; D007700:Kinetics; D008562:Membrane Glycoproteins / Q000378:metabolism*; D009414:Nerve Growth Factors / Q000378:metabolism / Q000494:pharmacology; D009419:Nerve Tissue Proteins / Q000494:pharmacology; D009474:Neurons / Q000166:cytology; D020933:Neurotrophin 3; D020812:Receptor, trkC; D012160:Retina / Q000196:embryology* / Q000378:metabolism; D013997:Time Factors
D003432:Cross-Linking Reagents; D007457:Iodine Radioisotopes; D008562:Membrane Glycoproteins; D009414:Nerve Growth Factors; D009419:Nerve Tissue Proteins; D020933:Neurotrophin 3; D020812:Receptor, trkC; D005022:Ethyldimethylaminopropyl Carbodiimide