EXPRESSION OF THE GROWTH-ASSOCIATED PROTEIN B-50 GAP43 VIA A DEFECTIVE HERPES-SIMPLEX VIRUS VECTOR RESULTS IN PROFOUND MORPHOLOGICAL-CHANGES IN NONNEURONAL CELLS/

This study describes the creation and application of a defective herpe s simplex viral (HSV) vector for B-50/GAP-43, a neural growth-associat ed phosphoprotein. We demonstrate abundant expression of B-50/GAP-43 i n cultured non-neuronal cells (African green monkey kidney cells [vero cells] and Rabbit skin cells) via this HSV vector. When B-50/GAP-43 w as expressed in non-neuronal cells major morphological changes occurre d that included extensive membrane ruffling, the formation of filopodi a and long thin extensions reminiscent of neurites. These extensions o ften terminated in growth cone-like structures. Quantitation of these morphological changes at different times following infection demonstra tes that the surface area of the B-50/GAP-43-expressing cells started to increase between 6 and 10 h post-infection. At 72 h, B-50/GAP-43-po sitive cells were 3.0 times larger in size and one third of the cells expressed long processes with a mean length of 165 +/- 14.5 mu m. Ultr astructural studies of cells 48 h after infection revealed that B-50/G AP-43 is predominantly localized at the plasma membrane of the elabora ted processes. Some immunoreactivity was associated with vesicular str uctures that appear to be in-transit in the processes. These observati ons suggest that B-50/GAP-43 acts at the plasmamembrane to induce a ne uron-like morphology in non-neuronal cells persisting for several days in culture. In the future the defective viral vector will enable gene transfer to express B-50/GAP-43 in neurons in vivo in order to study its involvement in regenerative sprouting and neuroplasticity.