Fig. 1. MAP1B, MAP1B-P and GSK3ß levels during PC12 cell differentiation. (A) Immunoblot analysis of whole-cell extracts from PC12 cells treated with NGF from 0 to 5 days, showing the levels of MAP1B, MAP1B-P and GSK3ß during cell differentiation. Note MAP1B is not phosphorylated by GSK3ß prior to NGF treatment. (B) Time course of cell differentiation for PC12 cells treated with NGF from 0 to 5 days (defined as the percentage of cells bearing processes equal or greater in length than one cell diameter). (C) Average PC12 neurite length measured after zero, one, three and five DIV following NGF addition (B and C are means±s.e.m. from four independent experiments). (D-F) Quantitative immunoblot analysis of the levels of MAP1B (D), MAP1B-P (E) and GSK3ß (F) from PC12 cells treated with NGF from 0 to 5 days. Results are expressed as a proportion of the protein levels after five DIV and are means±s.e.m. from four independent experiments. MAP1B expression is closely related to cellular differentiation, whereas MAP1B-P expression is delayed by one to two days. GSK3ß levels change relatively little during differentiation, in contrast to the levels of MAP1B phosphorylation (i.e. MAP1B-P expression).