(A) PAK1 functions downstream of Raf. Day 4 mature osteoclasts were infected with vector, caPAK1, dnRaf, or caPAK1 and dnRaf adenoviruses for 18 hours. Following infection, osteoclasts were serum starved and treated with 25 ng/ml M-CSF for eight hours. Shown are Percent Apoptotic Osteoclasts. (B) PAK1 and MEK have separate functions. Day 4 mature osteoclasts were infected with vector, caMEK, dnPAK1, or caMEK and dnPAK1 adenoviruses for eighteen hours. Following infection, osteoclasts were serum starved and treated with M-CSF for eight hours. Shown are Percent Apoptotic Osteoclasts. *p<0.05 compared to vector infection.