SECRETION OF ACID HYDROLASES AND ITS INTRACELLULAR SOURCE IN TETRAHYMENA PYRIFORMIS

Abstract

Axenic Tetrahymena pyriformis, syngen 1, mating type II cells were grown in Cox's defined medium . When washed and transferred into nonnutrient dilute salt solution or resuspended in the defined medium, the intact cells secrete acid hydrolases into the medium . Cells starving in the salt solution release in 5 hr about two-thirds of their ß-glucosidase, ß-N-acetylglucosaminidase, a-glucosidase, and amylase activities, about one-third of their deoxyribonuclease and phosphatase activities, smaller amounts of ribonuclease, and only a negligible fraction of their proteinase activity and protein content . During this period there is practically no change in the enzyme activities (except for a sudden increase of ribonuclease activity) and protein content of cells and medium together . Cells resuspended in the nutrient medium secrete enzymes as do the starved cells, but replace this loss, so that there is a continuous increase of the activities in the total system . According to isopycnic centrifugation experiments performed in sucrose gradients, the source of the hydrolases is a special population of lysosomes which disappear from the cells during starvation . This population equilibrates in the high density region of the gradients and contains the various acid hydrolases in about the proportion in which these enzymes appear in the medium . INTRODUCTIONIt has been reported that certain hydrolases appear in the medium of cultures of Tetrahymena pyriformis, a phagotrophic ciliated protozoan (see reference 14) . The nature and significance of this phenomenon is not understood . In the present paper we report quantitative data on the process of acid hydrolase secretion by Tetrahymena cells kept in nonnutritive or nutritive medium, and we show that it is a normal process not due to cell destruction . Furthermore, we present isopycnic centrifugation data showing that the source of the released enzymes is one of the two distinct populations of lysosomes that have been identified in this organism (16) . An abstract of this work has been published (15) . MATERIALS AND METHODS Organism and CultureTetrahymena pyriforrnis, syngen 1, mating type II (WH 14 strain) was cultured in the defined medium of Cox et al . (3) supplemented with glycine (35 mg/ 100 ml), L-proline (20 mg/100 ml), L-serine (20 mg/ 100 ml), and Na-ß-glycerophosphate (200 mg/100 nil) . The pH of this medium is about 5 .4. Mass cultures were grown in flat cylindrical flasks, 7 inches in diameter, (Jobling No . 1420 culture flasks, Laboratory Glassblowers Company, Sands, High Wycomb, Buckinghamshire, England), containing 500 ml of medium. These flasks were inoculated with 50 nil of a 2 day old culture, and grown unshaken at 30°f 0 .5°C for 2 days . By this time, the cultures

On starvation-induced autophagy in Teraahymena

“…In no case was enclosure of nucleoli, or other nuclear material, seen as reported by others ( 19); only cytoplasmic components were found in autophagosomes. Starvation of Tetrahymena occurs at the expense of protein (5,19,23), RNA (4,16,17), and phospholipids (13,18) which is in agreement with the observed sequestration of cell organelles, ribosomes, and membrane material. Moreover, the sequential removal of the various cell constituents indicates that autophagy occurs in a well-defined and controlled manner; however, no evidence was found to indicate how material to be sequestred may be selected.…”

Identification and partial characterization of an extracellular acid phosphatase activity of Leishmania donovani promastigotes.

“…In contrast, under these conditions, the exoenzyme was still inactive with this substrate. DISCUSSION Among microbial organisms, enzyme secretion is recognized in bacteria and fungi (8,15), free-living protozoa (11,16), and algae (12,13). To our knowledge, exoenzymes have not previously been characterized from parasitic protozoa.…”

In Vitro Synthesis and Secretion of Lysozyme by Mononuclear Phagocytes

“…The relationship between the intracellular lysozyme compartment and the lysosomal system of the macrophage (29) is also obscure. Separate populations of lysosome-like granules could be designed for export from the cell, as in Tetrahymena (30). During the early stages of human monocyte differentiation the promonocytes contain granules, corresponding to primary lysosomes, which contain peroxidase, arylsulfatase, and acid phosphatase (31).…”