PAN-NEUROTROPHIN-1 - A GENETICALLY-ENGINEERED NEUROTROPHIC FACTOR DISPLAYING MULTIPLE SPECIFICITIES IN PERIPHERAL NEURONS IN-VITRO AND IN-VIVO

Pan-neurotrophin 1 (PNT-1) is a synthetic trophic factor engineered by combining active domains of the neurotrophins nerve growth factor (NG F), brain-derived neurotrophic factor (BDNF), and neurotrophin 3 (NT-3 ) into an NT-3 backbone. This molecule was produced in transiently tra nsfected COS cells or in baculovirus-infected insect cells and subsequ ently purified to homogeneity. Saturation binding in embryonic spinal sensory neurons demonstrated a greater number of high-affinity binding sites for PNT-1 than for its parental molecule NT-3. PNT-1 was shown to efficiently block the chemical crosslinking of NGF, BDNF, and NT-3 to their cognate Trk receptors and to the low-affinity NGF receptor ex pressed on neuronal and nonneuronal cells. PNT-1 stimulated survival a nd proliferation of MG87 fibroblasts expressing either TrkA, TrkB, or TrkC. PNT-1 also promoted survival of a greater number of embryonic do rsal root ganglion neurons than any of the other neurotrophins alone, and its effects were equivalent to a combination of NGF, BDNF, and NT- 3. Analysis of receptor-specific neurotrophic activities demonstrated that PNT-1 efficiently rescued TrkA mRNA-containing sympathetic neuron s and TrkB and TrkC mRNA-containing sensory neurons from the dorsal ro ot and nodose ganglia. Finally, PNT-1 showed robust retrograde transpo rt to DRG neurons in vivo after injection into the sciatic nerve. Radi olabeled PNT-1 accumulated in small-, medium-, and large-sized neurons . Coinjection with different unlabeled neurotrophins inhibited PNT-1 t ransport in distinct subpopulations of neurons of different sizes, sug gesting that this molecule affects sensory neurons of different modali ties. These results indicate that PNT-1 is a potent and multispecific neurotrophic factor that may be useful in the treatment of peripheral neuropathies and nerve damage.