Problem
APX-1 is a juxtacrine signaling molecule expressed by P2. The receptor, expressed by ABa and ABp, is GLP-1.
1. What does juxtracrine mean?
2. How do we know that ABa also expresses GLP-1? Use the term "competent" in your answer.
3. Explain why it is critical that a juxtacrine signal from P2 is used to induce the differentiation of ABp, instead of paracrine signal.