The effects of ceramide and its analogues on the secretion of the mucocyst content of Tetrahymena

Monoclonal antibody to Geodia lectin is bound by the mucocyst content of Tetrahymena. By using this (fluorescent-labelled) antibody and confocal microscopy, the actual state of the mucocyst (position, resting, filling or extruding) can be studied. Treatment with C2 ceramide and non-hydroxy fatty acid caused a rapid depletion of mucocyst material. Another ceramide analogue, psychosine caused fusion of mucocysts. In these cases--in contrast to the controls--the contractile vacuole was filled with mucocyst material and this was seen in the tubules in contact with the contractile vacuoles. Hydroxy fatty acid ceramide, sphingomyelin and sphingosine-1-phosphate were ineffective. As the former materials influence also the cytoskeleton, while the latter do not, the cytoskeleton is presumed to have a mediatory effect. Neither the connection of contractile vacuoles with tubular structures nor mucocyst fusion have been described before.