AP2-mediated CD79-driven Endocytosis is Regulated in Cis via ITAM-embedded DCSM and QTAT motifs.

Panel A, Binding of AP2-btn to bead-captured GST bearing the indicated CD79a or CD79b cytoplasmic domains with the indicated mutations was determined as in Figure 3. Binding is expressed as a percentage of wild type CD79a binding and represents the mean of 3 independent experiments ± SEM. Statistical comparisons were measured between the non-mutated CD79a or CD79bDCSM cytoplasmic domains and other samples. Panels B and C, Endocytosis of the indicated MHC class II-CD79 fusion proteins was analyzed and quantitated as in Figure 1. Statistical comparisons were made between the reporter protein expressing the wild type CD79a or CD79b cytoplasmic domains and other reporter proteins. Panel D, Diagrammatic representation of cis and trans regulation of BCR AP2 binding and endocytosis. The open arrows indicate cis regulation by the DCSM and QTAT regulatory motifs. The closed arrows represent trans regulation of the endocytic activity of each cytoplasmic domain by the presence of the partner cytoplasmic domain.