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. 2003 Jun 15;23(12):5149–5160. doi: 10.1523/JNEUROSCI.23-12-05149.2003

Figure 2.

Figure 2.

Cortical progenitors are responsive to exogenous and endogenous neurotrophins. a, Left, Cortical progenitors cultured for 2 d (CORTICAL PROGENITOR) with 40 ng/ml FGF2, postmitotic cortical neurons (PM) were washed and then stimulated for 10 min with one of the four neurotrophins, NGF, BDNF, NT-3 or NT-4 and immunoprecipitated with an antibody to all Trk receptors (IP: Pan-Trk), and the immunoprecipitates were then analyzed by Western blot analysis with an antibody to phosphotyrosine (Probe: P-Tyr). The arrow indicates the phosphotyrosine-positive band migrating at the size of the Trk receptors. BDNF, NT-3, and NT-4, but not NGF, induce Trk tyrosine phosphorylation. Right, Cortical progenitors (CORTICAL PROGENITOR; 2 DIV) cultured with FGF2 (40 ng/ml) and postmitotic cortical neurons (PM) were analyzed for endogenous Trk receptor activation, as described above, without washing or exogenous neurotrophin stimulation. b, Cortical progenitor cells, cultured for 4 hr (without FGF2), were acutely stimulated with NGF, BDNF, NT-3, or FGF2 and analyzed by Western blot for the activation of Akt and ERKs, using phosphorylation-specific Akt (P-Akt) and ERK (P-ERK) antibodies. The same blots were then reprobed for total Akt and ERK protein as a loading control. BDNF, NT-3, and FGF2 all caused increased Akt and ERK phosphorylation, relative to cells that were either unstimulated (CTL) or stimulated with NGF. c, Western blot analysis for Akt and ERK activation in cortical progenitors cultured for 18 hr in the presence of FGF2 (40 ng/ml) and antibodies specific for BDNF (anti-BDNF; 20 μg/ml), NT-3 (anti-NT-3; 20 μg/ml), or control anti-chicken IgY (Ctl-IgY; 40 μg/ml). Western blots were first probed for the activated, phosphorylated forms of Akt and the ERKs (P-Akt and P-ERKs) and then reprobed for total Akt and ERK protein as a control for equal amounts of protein.