MELANOMA DYNEIN - EVIDENCE THAT DYNEIN IS A GENERAL MOTOR FOR MICROTUBULE-ASSOCIATED CELL MOTILITIES

Abstract

Platyfish-swordtail hybrid melanoma cells exhibit pigment aggregation in response to adrenergic stimulation or melanophore-concentrating hormone. This translocation of pigment granules is thought to be related to radially arrayed micotubules. Very little is known about the molecular "motor" that powers the translocation. We present evidence that dynein is located on these microtubules and is a candidate for the "motor". Vanadate and erythro-9-[3-(2-hydroxynonyl)]adenine, which are potent inhibitors of dynein ATPase prevent the transport of melanosome granules in Brij-treated melanoma cells. Direct identification of dynein in melanoma cells and tissues is demonstrated by immunofluorescence microscopy and immunoblotting using anti-fragment A (tryptic fragment of sea urchin sperm dynein) serum. The cytoplasm of melanoma cells is stained with the antiserum and gives rise to a pattern similar to the distribution of microtubules. Western blotting shows that the molecular weight of an immunoreactive polypeptide in melanoma tissues coincides with that of the heavy chain of sea urchin sperm dynein.