Altered phosphorylation of cytoskeleton regulatory proteins in Pak2-null megakaryocytes. (A) Western blot analysis of phosphorylation levels of cytoskeletal regulatory proteins LIMK, cofilin, and Aurora A/B/C in in vitro-deleted bone marrow-derived megakaryocytes (CAG-Cre-ERT2+; Pak2f/f). Equal quantities of total cellular protein were loaded and phospho-protein content was detected with phospho-specific antibodies (pLIMK, pCofilin, and pAurora) and total protein antibodies. Actin served as a control for equal loading. Blots are representative of at least 4 independent experiments. (B) Band densities quantified as a ratio of phospho:total protein and calculated as percentage of control. Densitometry was quantified with Fiji-Image J Software (National Institutes of Health). *P < .01. (C) Model depicting Pak2 regulation of megakaryocyte polyploidization and proplatelet formation through control of actin and microtubule networks.
