Figure 6.

The cAMP-PKA-CREB-1 pathway in TF-1 cells. Forskolin treatment enhanced intracellular cAMP levels by directly activating membrane-bound AC. This resulted in activation of the PKA catalytic C subunits, which diffuse into the nucleus. Once inside, they phosphorylated CREB-1 activator isoforms. Activated CREB-1 binds to CREs in the HIV-1 and CXCR4 promoter/5′ UTRs, thereby increasing transcription. This may have resulted in increased surface levels of CXCR4 and an increase in HIV-1 susceptibility.