THE REGULATION OF ACTIN POLYMERIZATION IN DIFFERENTIATING U937 CELLS CORRELATES WITH INCREASED MEMBRANE LEVELS OF THE PERTUSSIS-TOXIN-SENSITIVE G-PROTEIN GI2

Undifferentiated U937 cells appear to lack a capacity to increase cellular F-actin. However, electropermeabilized cells gain the ability to respond in this way to a guanine nucleotide analogue, guanosine 5'-[gamma-thio]trisphosphate (GTP[S]) after 1 h of treatment with dibutyryl cyclic AMP (db-cAMP). The results reported here show that the levels of membrane association of the G-protein G(i)2-alpha increase with a time course identical with that of the GTP[S]-sensitivity of electropermeabilized cells. These results suggest that G(i)2-alpha may be involved in the signal-transduction pathway leading to actin polymerization in db-cAMP-differentiated U937 cells.