Plasma membrane localization of palmitoylated tubulin

PC12 pheochromocytoma cells incorporate [H-3]palmitic acid into tubulin in a time- and cell-density-dependent manner. The plasma membrane-enriched fra ction contains most of the radioactivity of the membrane pellet. While palm itoylated tubulin is found in both the cytoplasm and particulate fraction, the bulk of [H-3]palmitic acid bound to tubulin is present in the crude mem brane pellet and the tubulin extracted from the plasma membrane is more hea vily palmitoylated than that extracted from endoplasmic reticulum. Detergen t-extracted tubulin from plasma membrane is, to a large extent, polymerizat ion competent; a substantial fraction, increasing as a function of labeling time, is not hydroxylamine-labile. The requirement for detergent extractio n, the accompanying changes in tubulin properties and the present findings of preferential incorporation of labeled tubulin into plasma membranes, mak e it clear that direct incorporation of tubulin into the plasma membrane ca n occur. (C) 2001 Academic Press.