Figure 3.
The 20-kD COOH-terminal region of agrin is necessary and sufficient for induction of c-fos. (A) Cortical neurons were treated for 10 min with C-AgΔ20 alone or in the presence of 50 pM C-Ag95z8 or C-Ag95z0. Neither a subsaturating (50 pM) nor supersaturating (50 nM) concentration of C-AgΔ20 induced expression of c-fos, nor were they able to modulate the activity of the larger fragments. (B) In contrast, cortical cultures exhibited a concentration-dependent and saturable increase in response to C-Ag20z8 (open circles, broken line) or C-Ag20z0 (solid circles, solid line) similar to that seen with the C-Ag95z8/0 fragments. Data were normalized to the level of Fos expression induced by 50 pM C-Ag95z8 alone in A and maximal level of Fos expression in B. Each data point shows the mean of triplicate determinations from three independent experiments ± SEM. Curves were fit by single-site nonlinear regression model R2 ≥ 0.97. Background levels of Fos expression from mock-treated sister cultures have been subtracted.