Effects of phosphoprotein phosphatase inhibitors (phenylarsine oxide and cantharidin) on Tetrahymena.

Abstract

The effects of phenylarsine oxide (PAO) (phosphotyrosine phosphatase inhibitor) and cantharidin (serine/threonine phosphatase [PP2A] inhibitor) treatments were analysed on the synthesis of phospholipids and glycolipids, and on the cytoskeletal elements (F-actin and tubulin containing structures) of Tetrahymena pyriformis. Both phosphatase inhibitors reduced the amount of incorporated 32P of the whole phospholipid content, but the ratio of phosphatidylserine (PS) and phosphatidylcholine (PC) to the total phospholipid content increased. Both treatments influenced the phosphatidylinositol (PI) system. These inhibitors also influenced the incorporation of palmitic acid into the phospholipids: in general PAO decreased, whereas cantharidin increased the amount of incorporated palmitic acid; 1 microM cantharidin significantly increased the labelling of PE and PA. The incorporation of mannose and glucosamine was influenced differently by PAO and cantharidin treatments: the latter elevated, while PAO decreased the labelling of glycolipids with these sugars. The effects of these treatments were visible also in the case of confocal scanning laser microscopic (CSLM) images: after treatments with both inhibitors, the F-actin containing cortical elements were destroyed, but the tubulin containing ones (longitudinal and transversal microtubules, oral apparatus and deep fibres) did not display significant alterations. The different effects of phosphatase inhibitors were visible also on the scanning electron microscopic (sEM) images: cantharidin treatments (1 microM) decreased the amount of dissolved membrane lipids after chemical dehydration of the cells with 2, 2-dimethoxy propane (DMP), but in the case of treatments with 10 microM, the surface pattern of cells was similar to the controls. On the other hand, after PAO treatments the surface pattern of Tetrahymena showed significant alterations. Both phosphatase inhibitors inhibited the phagocytotic activity of the cells. On the basis of present experiments we suppose that these treatments are able to influence signalling systems (e.g. PI) of Tetrahymena, and also the structure of the cytoskeleton and the functions (e.g. phagocytosis) which are connected with skeletal elements.