Three-dimensional models of the npo A structure with eightfold symmetry The NPC consists of an assembly of eight spokes arranged around a central channel 4 The spokes are connected to rings at the nuclear and cvtoplasmic surfacesThree-dimensional models of the NPC ❖ A structure with eightfold symmetry ❖ The NPC consists of an assembly of eight spokes arranged around a central channel ❖ The spokes are connected to rings at the nuclear and cytoplasmic surfaces