Nucleoporins comprise a permeability barrier for the entry of soluble proteins.
MKS proteins regulate the entry of membrane proteins at the transition zone.
NPHP proteins are structural components of the transition zone and regulate protein entry.
The inositol 5-phosphatase INPP5E creates a PI(4)P environment in the cilium.
Extraciliary PI(4,5)P2 may regulate exocytosis and endocytosis adjacent to the cilium.