Characterization of the interaction between high-risk human papillomaviruses and the host protein kinase A pathway

High-risk human papillomaviruses (HPV) infect squamous epithelia and cause hyperproliferative lesions that can progress to cancer. During infection, the virus interacts with and regulates the host kinome, which has important implications for viral and cellular protein function. The cyclic AMP (cAMP) dependent protein kinase A (PKA) phosphorylates several viral proteins and altered activity of this pathway may be relevant for oncogenic progression of HPV infections; however, whether the virus modulates the activity of PKA during infection is unclear. Using a bioluminescent resonance energy transfer-based approach, HPV18 replication was consistently associated with increased activity of the PKA pathway, occurring concomitantly with increased levels of cAMP; this was partially dependent on the HPV E5 oncoprotein. Additionally, biochemical analysis showed that the virus interacted with a nuclear regulator of PKA RII signalling, the A kinase-anchoring protein 95 (AKAP95). This interaction was mediated by the PSD95/DLG/ZO-1 (PDZ) binding motif of the E6 oncoprotein, requiring the polarity protein hScrib and PKA. Intriguingly, E6 regulated AKAP95 PKA binding and silencing of the AKAP in a physiological HPV18 replication model showed that it regulated expression of E6 targets Dlg1, hScrib and p53. Thus, E6 targeting of AKAP95 may be relevant for control of nuclear PKA signalling in order to facilitate virus replication.