Gsα availability to cholera toxin-catalysed ADP-ribosylation is decreased in membranes of retinoic acid-treated leukemic cell lines HL-60 and THP-1. A posttranslational effect

Retinoic acid (RA) induces HL-60 and THP-1 leukemic cell lines to differentiate into granulocyte-like and monocyte-like cells. Limited data are available concerning the effects of RA on components of the cyclic AMP pathway in human myeloid leukemic cells. We showed previously a decrease in adenylate cyclase activity in the presence of histamine, prostaglandin E1 and forskolin in RA-treated HL-60 cells as compared to untreated cells. We examined the elements of the signal transduction pathway utilized by RA in the human myeloid cell line HL-60 and the human monocytic cell line THP-1. We therefore studied the effect of RA on the activity of the stimulatory G-protein (Gs). We demonstrate that addition of RA to two human myeloid leukemia cell lines, HL-60 and THP-1, does not induce a reduction of the 2 subunit of Gs (Gsα) RNA or Gsα protein in the plasma membrane but leads to a rapid decrease in the cholera toxin (CTX)-catalysed ADP-ribosylation of Gsα. In addition, this effect seems to be specific to RA, since there was no modification in Gsα ADP-ribosylation in the membranes of cells treated with dimethyl sulfoxide (DMSO), another inducer of differentiation in HL-60 cells.