Fig. 5. Tie2 expression in MPCs. (Top) Western-blot analysis (WB) of MPC protein extract immunoreacted for Tie2 demonstrated a 140 kDa band that migrated with the Tie2 band of the endothelial cell control (EC). RT-PCR confirmed expression of Tie2 in MPCs at the mRNA level. Endothelial cells (EC) were used as positive control. No PCR bands were detected in the absence of reverse transcriptase (data not shown). Specificity of the PCR products was confirmed by sequence analysis. (Bottom) Analysis of MPC protein extracts immunoprecipitated (IP) with an anti-Tie2 antibody and reacted with an anti-phosphotyrosine antibody (-pY) showed phosphorylation of the MPC Tie2 receptor upon stimulation with both Ang-1 and Ang-2. Stripping and reprobing of the membrane with an anti-Tie2 antibody (-Tie2) showed that equal amounts of Tie2 were present in each lane.

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