Tubulin polyglutamylase enzymes are members of the TTL domain protein family

Normal and prostate cancer cells display distinct molecular profiles of alpha-tubulin posttranslational modifications

BACKGROUND

Multiple diverse posttranslational modifications of alpha-tubulin such as detyrosination, further cleavage of the penultimate glutamate residue (Delta2-tubulin), acetylation, and polyglutamylation increase the structural and functional diversity of microtubules.

METHODS

Herein, we characterized the molecular profile of alpha-tubulin posttranslational modifications in normal human prostate epithelial cells (PrEC), immortalized normal prostate epithelial cells (PZ-HPV-7), androgen-dependent prostate cancer cells (LNCaP), transitional androgen-independent prostate cancer cells (LNCaP-cds and CWR22Rv1), and androgen-independent prostate cancer cells (PC3).

RESULTS

Compared to PrEC and PZ-HPV-7 cells, all cancer cells exhibited elevated levels of detyrosinated and polyglutamylated alpha-tubulin, that was paralleled by decreased protein levels of tubulin tyrosine ligase (TTL). In contrast, PrEC and PZ-HPV-7 cells expressed markedly higher levels of Delta2-tubulin. Whereas alpha-tubulin acetylation levels were generally equivalent in all the cell lines, PC3 cells did not display detectable levels of Ac-tubulin.

CONCLUSION

These data may reveal novel biomarkers of prostate cancer and new therapeutic targets.

Multiple tubulin forms in ciliated protozoan Tetrahymena and Paramecium species

Tetrahymena and Paramecium species are widely used representatives of the phylum Ciliata. Ciliates are particularly suitable model organisms for studying the functional heterogeneity of tubulins, since they provide a wide range of different microtubular structures in a single cell. Sequencing projects of the genomes of members of these two genera are in progress. Nearly all members of the tubulin superfamily (alpha-, beta-, gamma-, delta-, epsilon-, eta-, theta-, iota-, and kappa-tubulins) have been identified in Paramecium tetraurelia. In Tetrahymena spp., the functional consequences of different posttranslational tubulin modifications (acetylation, tyrosination and detyrosination, phosphorylation, glutamylation, and glycylation) have been studied by different approaches. These model organisms provide the opportunity to determine the function of tubulins found in ciliates, as well as in humans, but absent in some other model organisms. They also give us an opportunity to explore the mechanisms underlying microtubule diversity. Here we review current knowledge concerning the diversity of microtubular structures, tubulin genes, and posttranslational modifications in Tetrahymena and Paramecium species.

Localization of Golgi 58K protein (formiminotransferase cyclodeaminase) to the centrosome

In vertebrate cells, the centrosome consists of a pair of centrioles and surrounding pericentriolar material. Using anti-Golgi 58K protein antibodies that recognize formiminotransferase cyclodeaminase (FTCD), we investigated its localization to the centrosome in various cultured cells and human oviductal secretory cells by immunohistochemistry. In addition to the Golgi apparatus, FTCD was localized to the centrosome, more abundantly around the mother centriole. The centrosome localization of FTCD continued throughout the cell cycle and was not disrupted after Golgi fragmentation, which was induced by colcemid and brefeldin A. Centriole microtubules are polyglutamylated and stable against tubulin depolymerizing drugs. FTCD in the centrosome may be associated with polyglutamylated residues of centriole microtubules and may play a role in providing centrioles with glutamate produced by cyclodeaminase domains of FTCD.

Tetrahymena Genome Database (TGD): a new genomic resource for Tetrahymena thermophila research

We have developed a web-based resource (available at ) for researchers studying the model ciliate organism Tetrahymena thermophila. Employing the underlying database structure and programming of the Saccharomyces Genome Database, the Tetrahymena Genome Database (TGD) integrates the wealth of knowledge generated by the Tetrahymena research community about genome structure, genes and gene products with the newly sequenced macronuclear genome determined by The Institute for Genomic Research (TIGR). TGD provides information curated from the literature about each published gene, including a standardized gene name, a link to the genomic locus in our graphical genome browser, gene product annotations utilizing the Gene Ontology, links to published literature about the gene and more. TGD also displays automatic annotations generated for the gene models predicted by TIGR. A variety of tools are available at TGD for searching the Tetrahymena genome, its literature and information about members of the research community.

Back on track – On the role of the microtubule for kinesin motility and cellular function

The evolution of cytoskeletal filaments (actin- and intermediate-filaments, and the microtubules) and their associated motor- and non-motor-proteins has enabled the eukaryotic cell to achieve complex organizational and structural tasks. This ability to control cellular transport processes and structures allowed for the development of such complex cellular organelles like cilia or flagella in single-cell organisms and made possible the development and differentiation of multi-cellular organisms with highly specialized, polarized cells. Also, the faithful segregation of large amounts of genetic information during cell division relies crucially on the reorganization and control of the cytoskeleton, making the cytoskeleton a key prerequisite for the development of highly complex genomes. Therefore, it is not surprising that the eukaryotic cell continuously invests considerable resources in the establishment, maintenance, modification and rearrangement of the cytoskeletal filaments and the regulation of its interaction with accessory proteins. Here we review the literature on the interaction between microtubules and motor-proteins of the kinesin-family. Our particular interest is the role of the microtubule in the regulation of kinesin motility and cellular function. After an introduction of the kinesin-microtubule interaction we focus on two interrelated aspects: (1) the active allosteric participation of the microtubule during the interaction with kinesins in general and (2) the possible regulatory role of post-translational modifications of the microtubule in the kinesin-microtubule interaction.