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. 1998 Jul;9(7):1661–1674. doi: 10.1091/mbc.9.7.1661

Figure 5.

Figure 5

The 40-kDa tyrosine-phosphorylated polypeptide is SCAMP3. (A) IgA protease cleaves SCAMP3. NeoR cells were either unstimulated (lanes 1, 2, 5, and 6) or stimulated (lanes 3, 4, 7, and 8) with 100 ng/ml EGF for 30 min, lysed in CHAPS buffer, and immunoprecipitated with 7C12. Samples were either incubated in PBS alone (lanes 1, 3, 5, and 7) or in PBS plus 400 nM IgA protease (lanes 2, 4, 6, and 8) for 1 h. Samples were Western blotted for phosphotyrosine (αP-Tyr, left panel) or for SCAMP3 (3γ, right panel). “Sc3Δ” indicates the presence of the putative SCAMP3 cleavage fragment. (B) Transferrin receptor is not cleaved by IgA protease. NeoR cells were stimulated with EGF for 30 min, lysed in CHAPS buffer, and immunoprecipitated with anti-transferrin receptor antibody (H68.4). Samples were incubated in PBS alone (lane 1) or in PBS plus 400 nM IgA protease (lane 2) for 1 h. Immunoprecipitates were Western blotted for transferrin receptor and visualized using ECL.