A new holographic limit of AdS5 x S5
  We re-examine the projective lightcone limit of the gauge-invariant Green-Schwarz action on 5D anti-de Sitter x the five-sphere. It implies the usual holography for AdS5, but also (a complex) one for S5. The result is N=4 projective superspace, which unlike N=4 harmonic superspace can describe N=4 super Yang-Mills off shell. 
Machiko Hatsuda and Warren Siegel