Phorbol myristate acetate stimulates microtubule and 10-nm filament extension and lysosome redistribution in mouse macrophages.

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Abstract
Phorbol myristate acetate (PMA) stimulates cell spreading and fluid-phase pinocytosis in mouse peritoneal macrophages. Colchicine (10-5 M) and cytochalasin B (10-5 M) abolish PMA stimulated pinocytosis but have little effect on cellular spreading (Phaire-Washington et al.). It was shown here that PMA also alters the organization of the cytoskeleton and the distribution of organelles in these cells. Neither control nor PMA-treated macrophages contain actin cables. PMA-treated resident and thioglycolate-elicited macrophages exhibit beneath their substrate-adherent membranes many randomly distributed punctate foci that stain brightly for actin. The appearance and distribution of these actin-containing foci are not altered by colchicine (10-5 M) or cytochalasin B (10-5 M). In thioglycolate-elicited macrophages PMA causes the extension and radial organization of microtubules and 10 nm filaments, and promotes the movement of secondary lysosomes from their perinuclear location to the peripheral cytoplasm. Depending upon the concentration of PMA used, 45-71% of thioglycolate-elicited macrophages and 32-44% of proteose-peptone-elicited macrophages and numerous lysosomes, radiating from the centrosphere region, arranged linearly along microtubule and 10-nm filament bundles. Colchicine (10-5 M) and podophyllotoxin (10-5 M) prevent the radial redistribution of microtubules, 10-nm filaments, and lysosomes in these cells. Cytochalasins B and D (10-5 M) have no inhibitory effects on these processes. These findings indicate that microtubules and 10-nm filaments respond in a coordinated fashion to PMA and to agents that inhibit microtubule function; they suggest that these cytoskeletal elements regulate the movement and distribution of lysosomes in the macrophage cytoplasm.