Fig. 4. Phosphorylation of paxillin tyrosine residues 31 and 118 in endogenous paxillin is stimulated by IL-3 and inhibited by PMA. After a 6-hour IL-3 deprivation in Baf3 cells, an aliquot was treated for 30 minutes with 10 ng/ml IL-3, 100 nM PMA or their combination. Paxillin was immunoprecipitated (IP Paxillin) and analyzed on western blots with anti-paxillin antibody (IB Paxillin), mixture of anti-phosphotyrosine antibodies 4G10 and PY20 (IB:PY) or antibody specific to phosphorylated paxillin tyrosine residues 31 or 118 (IB pY31Paxillin or IB pY118Paxillin, respectively). The same blot was developed with polyclonal antibodies that recognized the paxillin-binding protein vinculin (IB Vinculin) to demonstrate equal levels of protein loading.