Intraflagellar transport (IFT) is the bidirectional movement of protein complexes called IFT particles along microtubules between the base and tip of cilia and flagella. IFT is required for the assembly and maintenance of cilia as well as their motility and signaling functions. IFT particles carry cargo proteins in both the anterograde direction towards the tip, driven by kinesin motors, and the retrograde direction back towards the base, driven by dynein motors. IFT forms a shuttle system that is essential for building and renewing these organelles.

1. Intraflagellar Transport
Presented by- Ravi Ranjan

2. • Cilia are tiny hair like appendages(0.25µm) in diameter with a bundle of
microtubules at their core; they are extended from the surface of many kinds of
cells and are found in most animal species, many protozoa, and some lower
plants.
• Functions of cilia and flagella are - for movement
- for collecting food particles
- sensory reception.
• They consist of a highly organized microtubule-based axoneme, consisting of 9
outer microtubule doublets and in motile cilia also 2 single central microtubules.

3. In figure:-
(c)Structure of flagellar axoneme seen in
electron micrograph.
(d)Cross section of Chlamydomonas
flagella, A and B- tubule of outer
microdoublet, CPP- projections from
central pair microtubules, FM-flagellar
membrane, IA- inner dynein arm,
OA-outer dynein arms, RS-radial spokes.
Source- Nature reviews/molcellbio/volume3/Nov-2002
• Dynein outer/side arms hydrolyze ATP to generate a sliding force between the
doublets.

4. • Intraflagellar transport (IFT) is required for the assembly and
maintenance of cilia, as well as the proper function of ciliary motility
and signaling.
• IFT is powered by molecular motors that move along the axonemal
microtubules, carrying large complexes of IFT proteins that travel
together as so-called trains.
• The multi-subunit IFT-complex, which acts as an adapter between the
motor proteins required for movement and the ciliary cargo proteins.

5. Mechanism of IFT
• MT-based motility in which IFT particles move bidirectionally in the
ciliary of flagellar membrane between the basal body and the distal
tip of axoneme.
Loading and assembly of IFT-motor-particle-cargo complex.
Anterograde movement by Kinesin-II motors along axoneme.
Remodeling of complex (kinesin-II becomes cargo)
Retrograde movement by IFT-dynein activation towards basal body.

6. The anterograde transport of IFT
particles, driven by Kinesin- II motors,
is used t transport cargo, including
the retrograde motor from basal body
to distal tip.
Retrograde IFT, driven by IFT-dyneins,
is used to recycle IFT particles and
anterograde motors back to the cell
body, forming a bi directional shuttle
system.
Source- Douglas G. Cole, 2003

7. Proteins involved in IFT machinery
Source-page 428, J M Scholey, Annu. Rev. Cell
Dev. Bio. 2003

8. Biological Functions of IFT
• Motility
• Cytokinesis
• Control of flagellar length
• Sensory transduction during mating
• Primary cilia in the kidney.

9. Thank You