Fig. 7. Differential cortactin phosphorylation. (A) Control RAW osteoclasts, (B) cells co-expressing GFP-actin and SrcY527F, or (C) cells co-expressing GFP-actin and Src251 were fixed and triple-stained for actin (act), cortactin (cor) and phosphorylated cortactin (cor pY421). (A) Cortactin/actin ratio image highlights cortactin association with both SZL structure and clustered podosomes. Note the dramatic decrease in cortactin phosphorylation at the SZL structure (cor pY421/cor ratio image). (B) In SrcY527F-expressing cells, cortactin phosphorylation is moderately increased (cor pY421/cor ratio). (C) In Src251-expressing cells, cortactin is highly phosphorylated (cor pY421/cor ratio). Bars, 10 µm.