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Journal of Cell Science, Vol 89, 515-520, Copyright © 1988 by Company of Biologists

Submitted on September 24, 1987
Accepted on December 16, 1987

Exocytosis, endocytosis and membrane recycling in Tetrahymena thermophila

ARNO TIEDTKE 1, PETER HÜNSELER 1, JORGE FLORIN-CHRISTENSEN 2, and MONICA FLORIN-CHRISTENSEN 3

1 Institute of Zoology, University of MünsterSchlo{beta}platz 5, D-4400 Münster, FRG
2 Center for Parasite and Vector Research, National University of La Plata, Calle 2, No. 584, 1900 La Plata, Argentina
3 Center for Parasite and Vector Research, National University of La PlataCalle 2, No. 584, 1900 La Plata, Argentina

Mutant and wild-type cell lines of Tetrahymena thermophila were used to investigate a possible connection between acid hydrolase secretion and the major processes through which membranes are recycled in this ciliated protozoon. These processes consist of food vacuole formation (endocytosis), and food vacuole egestion and mucocyst release (both exocytosis). We have found that a mutant (MS-1, see-) blocked in hydrolase secretion is not blocked in either food vacuole formation or egestion and that it has normal mucocyst exocytosis. Another line of experiments with wild-type cells showed also that hydrolase secretion and endocytosis are independent of each other. Thus, sucrose (0.1m) did not interfere with hydrolase secretion, but blocked food vacuole formation. Furthermore, release of acid hydrolases was selectively stimulated by dibucaine without any effect on food vacuole egestion. Finally, exocytosis of mucocysts could occur without simultaneous release of acid hydrolases, as when cells were exposed to (0.15M-NaCl, which evokes a massive secretory response of mucocysts. Our results demonstrate that formation and egestion of food vacuoles and exocytosis of mucocysts are unrelated to secretion of acid hydrolases. Furthermore, they suggest that secretion of acid hydrolases is not a secondary effect of membrane recycling through these processes.

Key words: membrane recycling, secretion, acid hydrolases, Tetrahymena thermophila

Submitted on September 24, 1987
Accepted on December 16, 1987






© The Company of Biologists Ltd 1988