SnapShot: Intraflagellar Transport

摘要

What regulates the number of IFT complexes per array? Do IFT-A and IFT-B form both heteromultimers and homomultimers within the arrays? What regulates cargo binding and the activity of kinesin-2 and cytoplasmic dynein? Does IFT particle movement occur in both directions on each of the doublet microtubules in the structurally asymmetric axoneme (where the outer dynein arm is missing on one doublet, and beak structures and a two-part hinge are present on some doublets)? Although membrane proteins within flagella are moved by IFT, the Chlamydomonas flagellar membrane protein agglutinin does not require IFT for transport into existing flagella. Therefore, is the movement of most membrane proteins into cilia IFT independent? What couples axoneme assembly to the mobilization of lipid and protein components of the ciliary membrane and axoneme disassembly to the concerted retrieval of the ciliary membrane? Are IFT20 (a Golgi protein) and IFT27 (a protein essential to the cell cycle) the only IFT proteins with both IFT-dependent and (seemingly) IFT-independent functions?