Analysis of the role of profilin in Tetrahymena thermophila

David Earl Wilkes, Purdue University

Abstract

Profilins are small ubiquitous proteins that are involved in the dynamics of the actin cytoskeleton. Investigations using yeast, a cellular slime mold, and fruit flies have shown that profilin functions in the process of cytokinesis. The work in this thesis used the ciliate Tetrahymena thermophila to examine at what stage of cytokinesis profilin is involved. Other roles for profilin in T. thermophila were also investigated. Tetrahymena cells provide a model system to distinguish between early and late defects in cytokinesis because of the different macronuclear and cell morphological phenotypes that develop. The cDNA of T. thermophila profilin was isolated. It was determined that a single profilin gene exists in this cell type and the gene encodes a single transcript. To determine the role of profilin in T. thermophila, cells were transformed with a construct that created ribosomes that contain rRNA with an insertion of an antisense fragment of the profilin gene. No profilin protein was observed in the transformants with the antisense insertion. The cells with reduced profilin expression became large and abnormally shaped and contained both multiple micronuclei and multiple macronuclei, indicating that profilin was important for both early and late cytokinesis. The reduction of profilin levels also caused defects in micronuclear positioning and phagocytosis. The micronuclei with abnormal positioning appeared to be stable and were not degraded. The defect in phagocytosis was due to both the loss of oral apparatuses and a deficiency in the formation of phagocytic vesicles.

Degree

Ph.D.

Advisors

Otto, Purdue University.

Subject Area

Cellular biology|Molecular biology

COinS