Differential effect of NCAM and FGF on Cbl-mediated ubiquitination of FGFR1 and the association of Cbl with FRS-2α. (A) Lysates (3 mg) from HA-FGFR1–transfected HeLa cells stimulated for 10 min with FGF-2 or FGL were immunoprecipitated (IP) with anti-HA and immunoblotted for ubiquitin (top) followed by immunoblotting for HA (bottom). Mock-transfected cells stimulated with FGF-2 were used as negative control. (B) Lysates (1 mg) from HeLa cells stimulated for 10 min with FGF-2 or FGL were immunoprecipitated with antibodies against FRS-2α and immunoblotted for Cbl (top) followed by immunoblotting for FRS-2α (bottom).