Novel Cytoskeletal Proteins in the Cortex of Tetrahymena¹

Abstract

An important unsolved problem lies in the mechanisms that determine overall size, shape, and the localization of subcellular structures in eukaryotic cells. The membrane skeleton must play a central role in these processes in many cell types, and the ciliate membrane skeleton, or epiplasm, offers favorable opportunities for exploring the molecular determinants of cortical organization. Among the ciliates, Tetrahymena is well suited for the application of a wide range of molecular and cellular approaches. Progress has been made in the identification and sequencing of genes and proteins that encode epiplasmic and cortical proteins. The amino acid sequences of these proteins suggest that they define new classes of cytoskeletal proteins, distinct from the articulin and epiplasmin proteins. We will also discuss recent in vivo and in vitro studies of the regulation of assembly of these cortical proteins. This will include information regarding the down-regulation of epiplasmic proteins during cleavage, their topographic regulation in the cell cycle, and the results of in vitro assembly and binding studies of the epiplasmic C protein.

The Epiplasm Gene EPC1 Influences Cell Shape and Cortical Pattern in Tetrahymena thermophila1

“…Using sophisticated immunological procedures, Huttenlauch et al (1998) have demonstrated the individuality of the two classes and have established the presence of both in Euglena , the dinoflagellate Amphidinium , and the ciliates Pseudomicrothorax, Paramecium, Tetrahymena , and Euplotes . The major proteins in the epiplasm of Tetrahymena , however, are proteins unrelated to these called EpiA, EpiB, and EpiC (Honts and Williams 2003; Williams et al 1995). These three proteins are present in large amounts and show overlapping but independent distributions in the epiplasm of the cell.…”

Structure and Protein Composition of a Basal‐Body Scaffold (“Cage”) in the Hypotrich Ciliate Euplotes

“…Curtenaz et al. ; Honts and Williams ; Keryer et al. ), is that antisera may be reacting with covalent modifications or particular motifs (e.g.…”

“…Numerous kinetosome‐associated proteins in the cortex of various ciliates have been described (Fleury et al. ; Honts and Williams ; Jerka‐Dziadosz et al. ; Keryer et al.…”

Localization by Indirect Immunofluorescence of Tetrin, Actin, and Centrin to the Oral Apparatus and Buccal Cavity of the Macrostomal Form of Tetrahymena vorax

“…Furthermore, the addition of calcium to a macrostomal population initiates cytopharyngeal pouch closure and subsequent food vacuole formation (Sherman, Buhse, and Smith 1981). It is especially intriguing that actin and centrin complexes have both been reported to contract in the presence of calcium (Huxley 1969; Salisbury et al 1984), and it has not escaped our attention that tetrins share some structural similarity with coiled‐coil actin‐binding proteins, such as myosin and spectrin (Brimmer and Weber 2000; Honts 1991; Honts and Williams 2003). With this in mind, it is also intriguing that MYO1, a myosin identified in Tetrahymena thermophila , has been localized by indirect immunofluorescence to the “basal bodies and associated fibrillar material in the oral apparatus” (Garces, Hoey, and Gavin 1995).…”

“…Anti‐tetrin antibodies have been localized by indirect im‐munofluorescence to the CC and at the ultrastructural level to a filamentous structure associated with the undulating membrane in Tetrahymena pyriformis (Dress et al 1992). Tetrins are considered novel Tetrahymena proteins, though some similarity has been noted with other coiled‐coil proteins, such as heavy chain myosins and spectrins (Brimmer and Weber 2000; Honts 1991; Honts and Williams 2003). …”