Growth-associated protein 43 is down-regulated in cultured astrocytes

Growth-associated protein 43 (GAP-43: other designations--pp46, F1, B-50, p-57) is an abundant, neural, membrane-associated protein involved in synaptic plasticity and regeneration. We recently reported that GAP-43 is present in plasma membranes of cultured rat astrocytes. In the present study the level of astrocytic GAP-43 was assessed by indirect immunofluorescence labeling of cells with a specific anti-GAP-43 serum and immunoblotting of plasma membrane proteins. The results indicate that all astrocytes from 1-day-old cortex contained GAP-43 and those differentiated in culture did not. Furthermore, GAP-43 decreased dramatically during 3 weeks in culture. These results are consistent with the developmental down-regulation of GAP-43 in vivo.