UP-REGULATED EXPRESSION OF DECAY-ACCELERATING FACTOR (CD55) CONFERS INCREASED COMPLEMENT RESISTANCE TO SPROUTING NEURAL CELLS

We studied gene expression in relation to induced neural differentiati on in a human neural crest-derived cell line, Paju. Messenger RNA isol ated before and after treatment with phorbol 12-myristate 13-acetate w as analyzed by differential display reverse transcription PCR. A stron gly up-regulated expression of decay-accelerating factor (DAF, CD55) w as found to parallel the induced neural sprouting while the expression of two other complement regulatory proteins (CD59/protectin, CD46/mem brane cofactor protein) remained unaltered during neural differentiati on. The increased membrane expression of DAF, which was also seen on n eural processes and growth cones, conferred elevated resistance to com plement-mediated lysis. Our findings suggest that in sprouting neurons DAF expression is upregulated to provide additional complement resist ance to pathfinding axons/dendrites invading new environment. It is al so suggested that membrane expression of DAF may constitute a marker o f growing and regenerating neurons.