Dibucaine-induced synchronous mucocyst secretion in Tetrahymena

Abstract

Synchronous secretion of all available mature mucocysts was induced in late log phase cultures of Tetrahymena thermophilia (B III) by the local anaesthetic dibucaine. No assembled fusion rosettes were seen within the plasma membrane after release until 2-3 hrs of regrowth, thus proving that the rosettes are not permanent sites within the plasma membrane but have to be reassembled each time for a new fusion event to occur. Concomitant with the reappearance of assembled fusion rosettes, the cell cytoplasm fills up with precursors of new mucocysts thus linking the two events together.

An endosomal syntaxin and the AP-3 complex are required for formation and maturation of candidate lysosome-related secretory organelles (mucocysts) inTetrahymena thermophila

“…To examine whether APM3 is required for mucocyst formation and/or exocytosis, we first tested the secretory response of ∆apm3 in response to dibucaine, which triggers synchronous mucocyst exocytosis (Satir, 1977). When wild-type cells are exposed briefly to dibucaine, the mucocyst contents are released as macroscopic protein aggregates and can be visualized after low-speed centrifugation as a thick, flocculent layer (Figure 2A, lower left).…”

An aspartyl cathepsin,CTH3, is essential for proprotein processing during secretory granule maturation inTetrahymena thermophila

“…To ask whether any of these genes is involved in mucocyst secretion, we first tested the exocytic response using a semiquantitative assay based on stimulation by dibucaine, which triggers mucocyst exocytosis (Satir, 1977; Cowan et al. , 2005).…”

Independent Transport and Sorting of Functionally Distinct Protein Families in Tetrahymena thermophila Dense Core Secretory Granules

“…However, the Alcian blue assay does not allow one to assess the extent of exocytosis, that is, the fraction of DCGs that have released their contents. A second compound that acts as a potent secretagogue in Tetrahymena is the local anesthetic dibucaine (26). When treated with dibucaine, wild-type cells release their DCG contents within seconds.…”