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 in the control of F‐actin levels, locomotion, pinocytosis, and cell shape in lymphocytes. The PKC inhibitor Ro 31‐8220 elicits a high proportion of polarized (ED 50 = 1,5 10 ‐6 M) and locomoting cells and reduces the relative amount of F‐actin (by 29% at 10 ‐5 M) in initially resting cells. Phorbol myristate ace tate (PMA) counterbalances the polarizing effect of Ro 31‐8220. This indicates that the spherical shape and the F‐actin content of resting cells are maintained by con stitutive PKC activity. PMA‐induced increases in fluid pinocytosis, F‐actin content, and formation of nonpolar cells with surface protrusion are suppressed by Ro 31‐8220 (IC 50 = 2–4 10 ‐7 M). Spherical cells and, at higher concentrations (ED 50 = 13 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 PKC 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 used as a tool in further experiments requiring locomoting lymphocytes. J . Leukoc. Biol. 57: 587–591; 1995.