JASPLAKINOLIDE, A NOVEL ACTIN TARGETING PEPTIDE, INHIBITS CELL-GROWTHAND INDUCES ACTIN FILAMENT POLYMERIZATION IN THE GREEN-ALGA MICRASTERIAS

Jasplakinolide, a naturally occurring cyclodepsipeptide from the marin e sponge Jaspis sp., known to induce actin polymerization and stabiliz ation in vitro, markedly influences the morphogenetic process in the g reen alga Micrasterias when used in concentrations higher than 3 mu M. Development of Micrasterias is inhibited or strongly retarded, malfor mations occur, and large vacuoles are formed. At the ultrastructural l evel, dense abnormal accumulations of filamentous structures have been found indicating actin filament polymerizing activities of the drug i n situ. Moreover, displacement of organelles and aggregations of endop lasmic reticulum (ER) cisternae have been observed. Microtubule (MT) a rrangement and MT-dependent processes remain undisturbed. Cells allowe d to recover from jasplakinolide treatment continue their growth but s how severe changes in the cell pattern and displacement of organelles, suggesting that even after removal of the drug, some basic features f or the morphogenetic process remain altered. Jasplakinolide might be a useful tool for investigations on actin-dependent processes in the fu ture. (C) 1997 Wiley-Liss, Inc.