N-TERMINAL CYSTEINES ESSENTIAL FOR GOLGI SORTING OF B-50 (GAP-43) IN PC12 CELLS

WE have examined the subcellular distribution of the growth-associated protein B-50 (GAP-43) in pheochromocytoma (PC12) cells, using confoca l microscopy. Proliferating PC12 cells contained very low levels of B- 50 in the cytosol. Enhanced expression of B-50 in these cells, evoked by either nerve growth factor (NGF) treatment or transient transfectio n with rat B-50 cDNA, led to Golgi sorting and membrane targeting of t he B-50 protein. Site directed mutagenesis of Cys(3)Cys(4) to Ser,Gly, in B-50 resulted in a cytosolic distribution. We conclude that Cys(3) and Cys(4) are essential for accumulation of B-50 both at the plasma membrane and in the Golgi apparatus of PC12 cells.