Dynactin phosphorylation is modulated in response to cellular effectors

Reversible protein phosphorylation has been implicated in the regulation of organelle transport by cytoplasmic dynein. Motor function may be modulated directly by the phosphorylation of dynein or through the phosphorylation of an accessory factor. Dynactin binds to cytoplasmic dynein and is a required activator for dynein-driven vesicular motility. In metabolic labeling studies we have determined that the p150(Glued) subunit of dynactin is a phosphoprotein. Treatment of Rat2 cells with okadaic acid or with activators of protein kinase A or protein kinase C caused a marked increase in the incorporation of P-32 into p150(Glued); the increased phosphorylation correlated with activated vesicular transport. Phosphoamino-acid analysis of p150(Glued) isolated from cells treated with okadaic acid or with activators of either protein kinase A or protein kinase C indicated exclusive labeling of phosphoserine. These results suggest that the phosphorylation of dynactin may serve to regulate intracellular transport catalyzed by cytoplasmic dynein. (C) 1997 Academic Press.