INHIBITION OF PROTEIN-KINASE-C RESULTS IN A SWITCH FROM A NONMOTILE TO A MOTILE PHENOTYPE IN DIVERSE HUMAN LYMPHOCYTE POPULATIONS

Circulating lymphocytes are rounded, non-motile cells which on contact with cytokines, specialized or activated endothelium, acquire a const antly shape-changing, polarized morphology which enables migration int o appropriate sites. The biochemical mechanisms which regulate this sw itch are not understood but the various stimuli may have a common fina l pathway. In this study we show that protein kinase C (PKC) inhibitor s of the bisindolylmaleimide type (GF 109203X, Ro 31-8220, CGP 41 251) induce resting, spherical lymphocytes to change rapidly (< 30 min) in to polarized, locomotory cells. This phenomenon was seen with diverse populations of blood T lymphocytes, tonsillar B cells and Jurkat and M olt4 T-cell lines. Consistent with this, down-regulation of PKC by chr onic treatment (44hr) with bryostatin also induced the polarized pheno type in blood lymphocytes and non-motile Molt4 cells. Conversely, trea tment of a spontaneously motile subline of Molt4 cells with various PK C activators caused a reversion to the non-motile phenotype within min utes. PKC activation must be sufficient to overcome the effects of a c onstitutively active phosphatase because bisindolylmaleimide induction of motility could be prevented by pretreatment of the cells with a ph osphatase inhibitor, calyculin A. It is concluded that, in resting lym phocytes, chronic activation of a PKC offsets the action of a constitu tively active phosphatase and the net result is maintenance of the non -motile state. Agents which alter the kinase/phosphatase balance in fa vour of dephosphorylation result in induction of the locomotory phenot ype.