Ser585 of β_c selectively couples to 14-3-3 and p85. CTL-EN cells expressing either the wtβ_c or the indicated β_c mutants were factor deprived for 12 hours in RPMI containing 0.5% FCS, after which the cells (2 × 10⁷ cells/stimulation) were stimulated with 50 ng/mL GM-CSF for 0, 5, and 15 minutes. Following stimulation, cells were lysed and cleared lysates were subjected to immunoprecipitation with either anti-β_c antibodies (A-B) or anti-Shc antibodies (C). Immunoprecipitates were then subjected to SDS-PAGE and immunoblotted with anti–phosphoserine-585, anti-p85, anti–14-3-3 (EB1), anti-β_c (1C1), anti–phospho-Tyr577, anti–phosphotyrosine (4G10), or anti-Shc.