Fig. 1. Topology of cloned TrkB and p75 fusion proteins. Green fluorescent protein (GFP) and red fluorescent DsRed was fused C-terminally to full length rat TrkB (TrkB.FL), yielding TrkB.FL-GFP and TrkB.FL-DsRed. Similarly, the truncated TrkB isoforms were constructed to yield TrkB.T1-GFP and TrkB.T2-GFP. As a control, unfused TrkB.T1 was cloned into the same vector. The intracellular domain of TrkB.T1 (black bar) was deleted in the construct T1ICD-GFP. C-terminal fusion of GFP to rat p75^NTR yielded p75-GFP. A dominant negative p75^NTR (lowermost construct) was generated by fusing DsRed to the transmembrane domain of p75^NTR. The grey vertical bar shows the location of the plasma membrane; the extracellular space is to the left. The p indicates the pre sequence directing the receptor mRNAs to the rough ER.