T lymphocyte-triggering factor of african trypanosomes is associated with the flagellar fraction of the cytoskeleton and represents a new family of proteins that are present in several divergent eukaryotes.
The trypanosome cytoskeleton consists almost entirely of microtubule-based structures. Although alpha- and beta-tubulin from Trypanosoma brucei have been well characterized, much less is known about other cytoskeleton-associated proteins in trypanosomes. Using biochemical fractionation, we demonstrate here that T lymphocyte-triggering factor (TLTF) from T. brucei is a component of the detergent-resistant and Ca(2+)-resistant fraction of the parasite cytoskeleton. This fraction contains the flagellar apparatus and a subset of cytoskeletal protein complexes that together function in cell motility, cytokinesis, and organelle inheritance. We also show that TLTF-related genes are present in several highly divergent eukaryotic organisms. Although the function of the corresponding proteins is not known, the mammalian TLTF-like gene (GAS11; growth arrest-specific gene 11) is up-regulated in growth-arrested cells and is a candidate tumor suppressor (Whitmore, S. A., Settasatian, C., Crawford, J., Lower, K. M., McCallum, B., Seshadri, R., Cornelisse, C. J., Moerland, E. W., Cleton-Jansen, A. M., Tipping, A. J., Mathew, C. G., Savnio, M., Savoia, A., Verlander, P., Auerbach, A. D., Van Berkel, C., Pronk, J. C., Doggett, N. A., and Callen, D. F. (1998) Genomics 52, 325-331), suggestive of a role in coordinating cytoskeleton activities. Consistent with this possibility, we show that the human GAS11 protein contains a 144-amino acid domain that co-localizes with microtubules when fused to the green fluorescent protein and expressed in mammalian cells. These findings suggest that TLTF represents a newly defined protein family, whose members contribute to cytoskeleton function in species as diverse as protozoa and mammals.
Hill
K L
KL
Department of Biochemistry and Interdepartmental Genetics Ph.D. Program, University of Iowa, Iowa City, Iowa 52242, USA. kenthill@mednet.ucla.edu
Hutchings
N R
NR
Grandgenett
P M
PM
Donelson
J E
JE
D000595:Amino Acid Sequence; D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D019556:COS Cells; D002118:Calcium / Q000378:metabolism; D003598:Cytoskeletal Proteins; D003599:Cytoskeleton / Q000378:metabolism*; D005407:Flagella / Q000378:metabolism*; D019084:Fluorescent Antibody Technique, Indirect; D049452:Green Fluorescent Proteins; D006801:Humans; D008164:Luminescent Proteins / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008870:Microtubules / Q000378:metabolism; D008954:Models, Biological; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D017434:Protein Structure, Tertiary; D015800:Protozoan Proteins / Q000737:chemistry* / Q000378:metabolism*; D012313:RNA / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014162:Transfection; D014346:Trypanosoma brucei brucei / Q000378:metabolism* / Q000502:physiology*; D015854:Up-Regulation
D003598:Cytoskeletal Proteins; C115742:GAS8 protein, human; D008164:Luminescent Proteins; D009363:Neoplasm Proteins; D015800:Protozoan Proteins; D011993:Recombinant Fusion Proteins; C107172:T lymphocyte triggering factor, Trypanosoma brucei; D049452:Green Fluorescent Proteins; D012313:RNA; D002118:Calcium