Consider Agrin signaling in the formation of neuromuscular junctions in vertebrates. Shp2 is a protein tyrosine phosphatase that counteracts the tyrosine kinase activity of MuSK. Rapsyn interacts with the acetylcholine receptors and induces their agrin-dependent clustering. Indicate whether each of the following is expected to enhance (E) or suppress (S) acetylcholine receptor clustering in this process. Your answer would be a four-letter string composed of letters E and S only, e.g. EEEE.
( ) Specific inhibition of Shp2
( ) Loss of Rapsyn
( ) Loss of LRP4
( ) Constitutive activation of MuSK

Question

Consider Agrin signaling in the formation of neuromuscular junctions in vertebrates. Shp2 is a protein tyrosine phosphatase that counteracts the tyrosine kinase activity of MuSK. Rapsyn interacts with the acetylcholine receptors and induces their agrin-dependent clustering. Indicate whether each of the following is expected to enhance (E) or suppress (S) acetylcholine receptor clustering in this process. Your answer would be a four-letter string composed of letters E and S only, e.g. EEEE.
( )	Specific inhibition of Shp2
( )	Loss of Rapsyn
( )	Loss of LRP4
( )	Constitutive activation of MuSK

Quizplus · Accepted Answer

Agrin binding to LRP4 activates MuSK, leading to acetylcholine receptor clustering mediated by Rapsyn. As expected, loss of LRP4 or Rapsyn negatively affects receptor clustering and synapse formation. On the other hand, abnormal activation of MuSK or inhibition of its counteracting phosphatases leads to unnecessary clustering.

Consider Agrin Signaling in the Formation of Neuromuscular Junctions in Vertebrates