SELECTIVE RESPONSES (ACTIN POLYMERIZATION, SHAPE CHANGES, LOCOMOTION,PINOCYTOSIS) TO THE PKC INHIBITOR RO-31-8220 SUGGEST THAT PKC DISCRIMINATELY REGULATES FUNCTIONS OF HUMAN BLOOD-LYMPHOCYTES

The results suggest that protein kinase C (PKC) plays a pivotal role i n the control of F-actin levels, locomotion, pinocytosis, and cell sha pe in lymphocytes. The PKC inhibitor Ro 31-8220 elicits a high proport ion of polarized (ED(50) = 1.5 X 10(-6) M) and locomoting cells and re duces the relative amount of F-actin (by 29% at 10(-5) M) in initially resting cells, Phorbol myristate acetate (PMA) counterbalances the po larizing effect of Ro 31-8220. This indicates that the spherical shape and the F-actin content of resting cells are maintained by constituti ve PKC activity. PMA-induced increases in fluid pinocytosis, F-actin c ontent, and formation of nonpolar cells with surface protrusion are su ppressed by Ro 31-8220 (IC50 = 2-4 x 10(-7) M). Spherical cells and, a t higher concentrations (ED(50) = 3.3 x 10(-6) M), polarized cells are formed instead. As a result, lymphocyte function switches from fluid pinocytosis to cell polarity and locomotion. The data indicate that PR C is instrumental in selectively switching lymphocyte function between resting state, locomotor activity, and fluid pinocytosis. Ro 31-8220 is extremely potent in stimulating lymphocyte polarity and locomotion (B and T cells). It acts faster and/or produces a higher proportion of polarized lymphocytes than other available agonists, It may thus be u sed as a tool in further experiments requiring locomoting lymphocytes.