Figure 5
Mutations of Ser988 in the α4 cytoplasmic domain mimic phosphorylation. A) The amino acid sequence of the cytoplasmic domains of the α4 integrins expressed in PC12 cells, starting at the conserved juxtamembrane GFFKR sequence. As in Fig 1, the transmembrane and extracellular domains were wild-type human α4 integrin. The different mutations are underlined. B) The left panel shows an anti-phospho Ser988 α4 integrin blot of 1% Triton X-100 lysates of biotin-labelled PC12 cells expressing the different α4 constructs following immunoprecipitation with anti-human α4 extracellular domain antibodies and SDS-PAGE on 7% gels. Note that α4 integrins with the phospho-mimicking mutation S988D are labelled, while those with the S988A and control S990A mutations are not. Jurkat T cells are shown as a positive control. The right hand panel then shows the same blot stripped and reprobed with streptavidin peroxidase/ECL to confirm the similar expression of the different α4 constructs.