Blockage of tyrosine dephosphorylation of pre-patterned AChR clusters by NSC-treatment. R-BTX-labeled muscle cells were exposed to HB-GAM beads for 4 h in the absence (A-C) or presence of 1 μM NSC-87877 (D-F), fixed and then stained with anti-phosphotyrosine (mAb4G10) and FITC-conjugated secondary antibodies. In the example of the control muscle cell shown here, phosphotyrosine is detected at the bead-induced cluster (B, C; asterisks) but not at the pre-patterned cluster (B, C; arrow), but in the NSC-treated muscle cell, both the bead-induced cluster (E, F: asterisks) and the pre-patterned cluster (E, F: arrows) contain phosphotyrosine. G. Pooled data from multiple experiments were quantified after sorting the pre-patterned AChR clusters present on bead-stimulated cells as being fully tyrosine phosphorylated or partially or fully dephosphorylated. Control, n = 127; 0.1 μM NSC, n = 129; 1 μM NSC, n = 94; *p < 0.05 NSC relative to control.