GROWTH-ASSOCIATED PROTEIN-43 (GAP-43) FACILITATES PEPTIDE-HORMONE SECRETION IN MOUSE ANTERIOR-PITUITARY ATT-20 CELLS

The neuronal growth-associated protein (GAP)-43 (neuromodulin, B-50, F 1), which is concentrated in the growth cones of elongating axons duri ng neuronal development and in nerve terminals in restricted regions o f the adult nervous system, has been implicated in the release of neur otransmitter. To study the role of GAP-43 in evoked secretion, we tran sfected mouse anterior pituitary AtT-20 cells with the rat GAP-43 cDNA and derived stably transfected cell lines. Depolarization-mediated be ta-endorphin secretion was greatly enhanced in the GAP-43-expressing A tT-20 cells without a significant change in Ca2+ influx; in contrast, expression of GAP-43 did not alter corticotropin releasing factor-evok ed hormone secretion. The transfected cells also displayed a flattened morphology and extended processes when plated on laminin-coated subst rates. These results suggest that AtT-20 cells are a useful model syst em for further investigations on the precise biological function(s) of GAP-43.