  The Casimir energies for plate-sphere system and sphere-sphere system under
PFA in the presence of one extra compactified universal dimension are analyzed.
We find that the Casimir energy between a plate and a sphere in the case of
sphere-based PFA is divergent. The Casimir energy of plate-sphere system in the
case of plate-based PFA is finite and keeps negative. The extra-dimension
corrections to the Casimir energy will be more manifest if the sphere is larger
or farther away from the plate. It is shown that the negative Casimir energy
for two spheres is also associated with the sizes of spheres and extra space.
The larger spheres and the longer distance between them make the influence from
the additional dimension stronger.
