Gateway to the cilium

Courtesy of John Dishinger

The paper

J.F. Dishinger et al., “Ciliary entry of the kinesin-2 motor KIF17 is regulated by importin-b2 and RanGTP," Nat Cell Biol, 12:703-10, 2010. Free F1000 Evaluation

The finding

Primary cilia are tiny, hair-like organelles on the surface of cells, and are important in functions such as vision and smell. The composition of cilia membranes is different from the rest of the cell membrane due to a ring of proteins (septins) that act as a roadblock to diffusion. But how ciliary cytoplasmic proteins arrive at their specific destination was unknown. Kristen Verhey’s group at the University of Michigan Medical School identified a traffic-signaling sequence that cells append to proteins destined for the cilia.

The surprise

Verhey’s group was studying a kinesin motor protein called KIF17 when they noticed that some mutants did not enter the cilium. The mutant sequences had signaling...

The known

Verhey’s group showed that trafficking cytoplasmic proteins to the cilium involves the same cellular machinery—including the transport protein importin-β—used in nuclear import. The results suggest a common mechanism for trafficking cargo to different cellular compartments, writes Faculty Member Monica Bettencourt-Dias in her review.

The unknown

Although nuclear pores are well characterized, the nature of the cytoplasmic ciliary barrier isn’t known. Interestingly, nobody knows how the cell tells the difference between cargo destined for nuclear and ciliary sites.

F1000 evaluators: J. Bird and T. Friedman (NIDCD NIH) • M. Rape (Berkeley Univ) •
M. Bettencourt-Dias
(Inst Gulbenkian de Ciência, Portugal)

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