The p62 coprecipitating with Tec is p62Dok-1.

(A) Tec and Dok-1 were immunoprecipitated from whole cell lysates of nonstimulated and SCF-incubated F36P cells and analyzed by Western blotting with antiphosphotyrosine (PY99; top panel) and anti-Tec (lower panel). Two species of Dok-1 are phosphorylated by SCF (indicated by arrows), of which the upper one comigrates with Tec-associated p62. Proteins of 56 and 140 kd are observed in both Tec and Dok-1 precipitates of SCF-treated cells (indicated by arrows). (B) Lysates of SCF-stimulated F36P cells were precleared with anti-Dok-1, followed by Tec immunoprecipitation, or vice versa. The lysates were analyzed by Western blotting with antiphosphotyrosine (top panel) and anti-Tec (lower panel). Pretreatment of the lysates reduces the amount of phosphorylated p62/Dok-1, indicating that p62 is identical to the slower migrating species of Dok-1.