Article

Molecular Basis of Tubulin Transport Within the Cilium by IFT74 and IFT81

Department of Structural Cell Biology, Max Planck Institute of Biochemistry, Am Klopferspitz 18, D-82152 Martinsried, Germany.
Science (Impact Factor: 33.61). 08/2013; 341(6149):1009-12. DOI: 10.1126/science.1240985
Source: PubMed

ABSTRACT

Intraflagellar transport (IFT) of ciliary precursors such as tubulin from the cytoplasm to the ciliary tip is involved in
the construction of the cilium, a hairlike organelle found on most eukaryotic cells. However, the molecular mechanisms of
IFT are poorly understood. Here, we found that the two core IFT proteins IFT74 and IFT81 form a tubulin-binding module and
mapped the interaction to a calponin homology domain of IFT81 and a highly basic domain in IFT74. Knockdown of IFT81 and rescue
experiments with point mutants showed that tubulin binding by IFT81 was required for ciliogenesis in human cells.

Download full-text

Full-text

Available from: Philippe Bastin
  • Source
    • "The cargoes and binding sites of these complexes are currently being investigated, and protein-protein interaction experiments are aided by screens for proteins that exhibit IFT-like transport velocities through the cilium. For instance, as it pertains to ciliary length, tubulin has been shown to have direct binding affinity to IFT81 and IFT74[81]. Although there are several ciliary proteins that can be screened in this way, there are also numerous proteins, including tubulin, that appear to move into and through the cilium by diffusion and it has been shown that cargo from the anterograde complex is progressively unloaded and re-loaded throughout the journey up the axoneme[67,82,83]. "
    [Show description] [Hide description]
    DESCRIPTION: Cellular Mechanisms of Ciliary Length Control
    Full-text · Research · Jan 2016
  • Source
    • "The cargoes and binding sites of these complexes are currently being investigated, and protein-protein interaction experiments are aided by screens for proteins that exhibit IFT-like transport velocities through the cilium. For instance, as it pertains to ciliary length, tubulin has been shown to have direct binding affinity to IFT81 and IFT74 [81]. Although there are several ciliary proteins that can be screened in this way, there are also numerous proteins, including tubulin, that appear to move into and through the cilium by diffusion and it has been shown that cargo from the anterograde complex is progressively unloaded and re-loaded throughout the journey up the axoneme [67,82,83]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Cilia and flagella are evolutionarily conserved, membrane-bound, microtubule-based organelles on the surface of most eukaryotic cells. They play important roles in coordinating a variety of signaling pathways during growth, development, cell mobility, and tissue homeostasis. Defects in ciliary structure or function are associated with multiple human disorders called ciliopathies. These diseases affect diverse tissues, including, but not limited to the eyes, kidneys, brain, and lungs. Many processes must be coordinated simultaneously in order to initiate ciliogenesis. These include cell cycle, vesicular trafficking, and axonemal extension. Centrioles play a central role in both cell cycle progression and ciliogenesis, making the transition between basal bodies and mitotic spindle organizers integral to both processes. The maturation of centrioles involves a functional shift from cell division toward cilium nucleation which takes place concurrently with its migration and fusion to the plasma membrane. Several proteinaceous structures of the distal appendages in mother centrioles are required for this docking process. Ciliary assembly and maintenance requires a precise balance between two indispensable processes; so called assembly and disassembly. The interplay between them determines the length of the resulting cilia. These processes require a highly conserved transport system to provide the necessary substances at the tips of the cilia and to recycle ciliary turnover products to the base using a based microtubule intraflagellar transport (IFT) system. In this review; we discuss the stages of ciliogenesis as well as mechanisms controlling the lengths of assembled cilia.
    Full-text · Article · Jan 2016
  • Source
    • "During ciliary growth, IFT concentrates soluble tubulin in cilia and thereby promotes elongation of the axonemal microtubules. in vitro interaction between tubulin dimers and IFT74–IFT81 complexes (Bhogaraju et al., 2013). We designed modified GFP–-tubulins in which the E-hook was replaced with the corresponding region of -tubulin, altered to substitute seven glutamate residues with alanine or glutamine, or removed entirely (Table S1). "
    [Show abstract] [Hide abstract]
    ABSTRACT: The assembly of the axoneme, the structural scaffold of cilia and flagella, requires translocation of a vast quantity of tubulin into the growing cilium, but the mechanisms that regulate the targeting, quantity, and timing of tubulin transport are largely unknown. In Chlamydomonas, GFP-tagged α-tubulin enters cilia as an intraflagellar transport (IFT) cargo and by diffusion. IFT-based transport of GFP-tubulin is elevated in growing cilia and IFT trains carry more tubulin. Cells possessing both nongrowing and growing cilia selectively target GFP-tubulin into the latter. The preferential delivery of tubulin boosts the concentration of soluble tubulin in the matrix of growing versus steady-state cilia. Cilia length mutants show abnormal kinetics of tubulin transport. We propose that cells regulate the extent of occupancy of IFT trains by tubulin cargoes. During ciliary growth, IFT concentrates soluble tubulin in cilia and thereby promotes elongation of the axonemal microtubules. © 2015 Craft et al.
    Full-text · Article · Jan 2015 · The Journal of Cell Biology
Show more