PTEN regulates motility but not directionality during leukocyte chemotaxis

The localization at opposite cell poles of phosphatidylinositol-3 kinases and PTEN (phosphatase and tensin homolog on chromosome 10) governs Dictyostelium chemotaxis. To study this model in mammalian cells, we analyzed the dynamic redistribution of green fluorescent protein (GFP)-tagged PTEN chimeras during chemotaxis. N- or C-terminus GFP-tagged PTEN was distributed homogeneously in the cytoplasm of chemotaxing PTEN-negative Jurkat cells and PTEN-positive HL60 cells. Moreover, we did not detect uropod accumulation of endogenous PTEN in chemoattractant-stimulated HL60 cells. Cell fractionation indicated that both endogenous and ectopically expressed PTEN were confined largely to the cytosol, and that chemoattractant stimulation did not alter this location. PTEN re-expression in Jurkat cells or PTEN depletion by specific siRNA in HL60 cells did not affect cell gradient sensing; PTEN nonetheless modulated chemoattractant-induced actin polymerization and the speed of cell movement. The results suggest a role for PTEN in regulating actin polymerization, but not directionality during mammalian cell chemotaxis.