Tubulin-binding cofactor C domain-containing protein TBCCD1 orchestrates cytoskeletal filament formation

Abstract

TBCCD1 is an enigmatic member of the tubulin-binding cofactor C (TBCC) family of proteins required for mother-daughter centriole linkage in the green alga Chlamydomonas reinhardtii and nucleus-centrosome-Golgi linkage in mammalian cells. Loss of these linkages has severe morphogenetic consequences, but the mechanism(s) through which TBCCD1 contributes to cell organisation is unknown. In the African sleeping sickness parasite Trypanosoma brucei a microtubule-dominant cytoskeleton dictates cell shape, influencing strongly the positioning and inheritance patterns of key intracellular organelles. Here we show the trypanosome orthologue of TBCCD1 is found at multiple locations: centrioles, the centriole-associated Golgi ‘bi-lobe’, and the anterior end of the cell body. Loss of TbTBCCD1 results in disorganisation of the structurally complex ‘bi-lobe’ architecture and loss of centriole linkage to the parasite's single unit-copy mitochondrial genome (or kinetoplast). We therefore identify TBCCD1 as an essential protein associated with at least two filament-based structures in the trypanosome cytoskeleton. The last common ancestor of trypanosomes, animals and green algae was arguably the last common ancestor of all eukaryotes. Based on our observations, and interpretation of published data, we argue for unexpected co-option of the TBCC domain for an essential, non-tubulin related function, at an early point during evolution of the eukaryotic cytoskeleton.