CREB1 and infection: Hence, cells lacking P2X7R may prove less responsive to the sustained build-up of extracellular ATP that could accompany infection with pathogens like T. gondii. The downstream effect of this would be exactly what we see, that is, decreased levels of phospho-CREB and increased levels of phospho-NFκB following infection; however, NF-κB appears to be constitutively over-produced in P2X7R-/- mice, regardless of infection status.