Figure II.

Simplified Schematic of Protein Trafficking Into and Inside the Cilium. Proteins are transported to the base of the cilium by several pathways. This transport step involves BBS proteins, IFT20, and exocyst-related small Rab GTPases. IFT-B (yellow circles) and IFT-A (brown circles) complexes mediate anterograde and retrograde intraflagellar transport (IFT) along the axoneme. Vesicular trafficking and cargo transport are indicated by dashed black arrows. The permeability barrier called the ‘ciliary gate’, that is thought to consist of transition fibers, transition zone proteins (reviewed in [95]), and possibly nuclear pore components (such as nucleoporins), is indicated by the dashed pink ovals and pink shading. Selective trafficking of cargo proteins through the ciliary gate is indicated by the solid black arrow. For details see main text. The key on the left indicates the major protein components and complexes.