Ubiquitination of IGF-1R is phosphorylation dependent.

<p>After 24-h serum starvation wt IGF-1R (A) and K1003R (B) cells were stimulated for indicated time points with 50 ng/ml IGF-1. Lysates were immunoprecipitated (IP) with anti-IGF-1Rß (H60), and blotted with either anti-phosphotyrosine (pY99) or anti-ubiquitin (p4D1). The graphs represent quantification (% of loading control) of three independent experiments. Means and SDs are shown. Equal loading was confirmed by stripping and re-immunoblotting with anti-IGF-1Rß (C20).