Integrin α2β1 is intimately associated with SHP-1. (A) Total HUVEC lysates from cells grown on collagen and stimulated with 25 nM endorepellin for 0, 2, 5, 10, or 30 minutes were immunoprecipitated (IP) with an integrin α2 antibody and immunoblotted (IB) with antibodies against integrin α2, phosphotyrosine residues (PY20), or SHP-1. (B) Quantification of SHP-1 associated with the integrin α2 subunit from experiments as shown in panel A. Means ± SEMs (n = 3); *P < .05. (C) Quantification of phosphorylated SHP-1. Means ± SEMs (n = 3). (D) Cell lysates treated as in panel A were immunoprecipitated with SHP-1 and probed for integrin α2, SHP-1, and phosphotyrosine. (E) Tyrosine phosphatase activity of immunoprecipitated SHP-1 from HUVECs treated with endorepellin (25 nM) for the indicated time intervals. The values in the bottom panel represent means ± SEMs (n = 3). (F-G) Immunoprecipitation of SHP-1 in C2C12 and UB cells with the designated genotypes after endorepellin treatment (25 nM) for 0, 5, and 40 minutes (F) and for 5 minutes (G). The values in the bottom panel represent means ± SEMs (n = 3).