The relationship of protein synthesis to cell division and oral development in synchronized Tetrahymena pyriformis GL‐C: An analysis employing cycloheximide

Abstract

The effects of cycloheximide on synchronized Tetrahymena pyriformis strain GL-C were investigated at concentrations ranging from 0.01 to 10 pg/ml.The initial inhibition of protein synthesis was nearly total (> 85% ) at 1 pg/ml and above, partial (SO-SO%) at 0.2 to 0.05pg/ml, and slight (< 30%) at O.O2pg/ml.Eventual recovery of protein synthesis to a rate approaching that of the controls took place at concentrations of lpg/ml and less. When the drug was added before a "transition point" at 55 minutes after the end of the synchronizing treatment (EST), cell division was blocked by 10 pg/ml, and delayed at concentrations of 1 pg/ml or less. The duration of delay was related to the degree of initial inhibition, and to the time required for recovery of protein synthesis; it also depended on the time after EST at which the drug was added. At a given concentration, maximum division delay was observed just prior to the "transition point;" this maximum delay was correlated with resorption of differentiating oral primordia, followed by the appearance of new primordia. The lesser delays observed at earlier times were correlated with temporary blockage of development of primordia in the "stomatogenic field" stage. Resumption of oral primordium development was, in both cases, temporally correlated with a substantial recovery of protein synthesis. After the "transition point," cell division, and completion of oral development, was delayed slightly at the lower concentrations, and more substantially at 1 and 10,ug/ml, with some division-arrest at the latter concentration. Except for the recovery phenomenon, the developmental responses elicited by cycloheximide were similar to those observed earlier with puromycin.The bearing of these findings on the mechanism of synchronization in Tetruhymenu is considered in the Discussion.Studies employing two antagonists of protein synthesis, p-fluorophenylalanine and puromycin, have provided evidence that concurrent protein synthesis is necessary to support preparation for cell division (Rasmussen and Zeuthen, '62) and oral development (Frankel, '62, '67b) in strain GL of the ciliate Tetrahymena pyriformis. The earlier studies, utilizing brief doses of p-fluorophenylalanine, demonstrated that treatment prior to a certain stage could bring about a "set-back" of cell division (Rasmussen and Zeuthen, '62) with attendant arrest or resorption of the developing oral primordium (Frankel, '62); after this stage (which is known as the "physiological transition point" or "stabilization point") the inhibitor had no effect. A later study with puromycin (Frankel, '67b) yielded generally similar results; however, it also revealed that a high concentration of the inhibitor, which caused J. CELL. PHYSIOL., 74: 135-148.

The Vegetative Micronucleus has a Critical Role in Maintenance of Cortical Structure in Tetrahymena thermophila.

“…1). This result is different from that of colchicine reported by Nelsen (17) (6,7). In the present results, the amicronucleate cell was produced from both the anterior or the posterior part of a cell in a random fashion, and the sister cell with micronucleus did not lose the OAbut grew normally when it was transferred to the culture medium(data not shown).…”

The Effects of Supraoptimal Temperatures on Population Growth and Cortical Patterning in Tetrahymena pyriformis and Tetrahymena thermophila: A Comparison

“…The third peculiarity in the response of T. pyriformis to supraoptimal temperatures is a severe abnormality in the patterning of the developing oral structures destined for the posterior division products, which is manifested at the temperatures that bring about the transient recovery of cell division described above (Frankel 1964). Such a developmental abnormality was not observed during transient inhibition of cell division by the protein synthetic inhibitor cycloheximide (Frankel 1969), but was observed with the microtubule inhibitor colchicine (Nelsen 1970). …”

An Evaluation of Hsp90 as a Mediator of Cortical Patterning in Tetrahymena

“…Second, the residues in the N‐terminal domain of the Hsp90 molecule critical for geldanamycin‐ (and ATP ‐) binding are highly conserved in the T. thermophila hsp82p and the T. pyriformis hsp81p. Third, the effects of geldanamycin on patterning of the oral apparatus are quite unlike those observed earlier with inhibitors of macromolecular synthesis, notably cycloheximide (Frankel 1969). …”