Tyrosine-phosphorylation of MAGI proteins. (a) Phosphorylation of MAGI-1 by ERB-receptor kinases. Cells were transfected with MAGI-1, in the presence or absence of ERBB2, ERBB3 and ERBB4 and tyrosine phosphorylation of MAGI-1 determined. (b) Phosphorylation/dephosphorylation of MAGI-1. Cells were transfected with MAGI-1, ERBB2 and ERBB4, in the presence or absence of RPTPβ. Transfected cells were treated with vehicle or NRG1, and tyrosine phosphorylation of MAGI-1 determined. Similar results were observed with MAGI-2 (data not shown).