Neutrophils stimulated with a variety of structurally diverse chemoattractants exhibit rapid activation of p21-activated protein kinases (Paks). Regulation by sphingolipids: R.Y. Huang, J.P. Lian, D.R. Robinson, and J.H. Badwey Arthritis Unit, Massachusetts General Hospital, Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, and the Boston Biomedical Research Institute, Boston, MA USA 02114