DIFFERENTIAL ROLE OF THE LOW-AFFINITY NEUROTROPHIN RECEPTOR (P75) IN RETROGRADE AXONAL-TRANSPORT OF THE NEUROTROPHINS

The receptor mechanisms mediating the retrograde axonal transport of t he neurotrophins have been investigated in adult rats. We show that tr ansport of the TrkB ligands NT-4 and BDNF to peripheral neurons is dep endent on the low affinity neurotrophin receptor (LNR). Pharmacologica l manipulation of LNR in vivo using either an anti-LNR antibody or a s oluble recombinant LNR extracellular domain completely blocked retrogr ade transport of NT-4 and BDNF to sensory neurons, while having minima l effects on the transport of NGF in either sensory or sympathetic, ne urons. Furthermore, in mice with a null mutation of LNR, the transport of NT-4 and BDNF, but not NGF, was dramatically reduced. These observ ations demonstrate a selective role for LNR in retrograde transport of the various neurotrophins from distinct target regions in vivo.