Viruses have evolved an assortment of mechanisms for regulating the Akt signaling pathway to establish a cellular environment more favorable for viral replication. Myxoma virus (MYXV) is a rabbit-specific poxvirus that encodes many immunomodulatory factors, including an ankyrin repeat-containing host range protein termed M-T5 that functions to regulate tropism of MYXV for rabbit lymphocytes and certain human cancer cells. MYXV permissiveness in these human cancer cells is dependent upon the direct interaction between M-T5 and Akt, which has been shown to induce the kinase activity of Akt. In this study, an array of compounds that selectively manipulate Akt signaling was screened and we show that only a subset of Akt inhibitors significantly decreased the ability of MYXV to replicate in previously permissive human cancer cells. Furthermore, reduced viral replication efficiency was correlated with lower levels of phosphorylated Akt. In contrast, the PP2A-specific phosphatase inhibitor okadaic acid promoted increased Akt kinase activation and rescued MYXV replication in human cancer cells that did not previously support viral replication. Finally, phosphorylation of Akt at residue Thr308 was shown to dictate the physical interaction between Akt and M-T5, which then leads to phosphorylation of Ser473 and permits productive MYXV replication in these human cancer cells. The results of this study further characterize the mechanism by which M-T5 exploits the Akt signaling cascade and affirms this interaction as a major tropism determinant that regulates the replication efficiency of MYXV in human cancer cells.

Autophagy is an intracellular turnover pathway. It has special relevance for neurodegenerative proteinopathies, such as Alzheimer disease, Parkinson disease, and Huntington disease (HD), which are characterized by the accumulation of misfolded proteins. Although induction of autophagy enhances clearance of misfolded protein and has therefore been suggested as a therapy for proteinopathies, neurons appear to be less responsive to classic autophagy inducers than nonneuronal cells. Searching for improved inducers of neuronal autophagy, we discovered an N(10)-substituted phenoxazine that, at proper doses, potently and safely up-regulated autophagy in neurons in an Akt- and mTOR-independent fashion. In a neuron model of HD, this compound was neuroprotective and decreased the accumulation of diffuse and aggregated misfolded protein. A structure/activity analysis with structurally similar compounds approved by the US Food and Drug Administration revealed a defined pharmacophore for inducing neuronal autophagy. This pharmacophore should prove useful in studying autophagy in neurons and in developing therapies for neurodegenerative proteinopathies.

This study was to evaluate the enhancement value of chloroquine (CQ) in cancer cell killing when used in combination with Akt inhibitors. The results showed that the combination of CQ and Akt inhibitors is much more effective than either one alone. Importantly, the CQ-mediated chemosensitization of cell killing effects by Akt inhibitors is cancer specific. In particular, when combined with 10 microM CQ, 1,3-dihydro-1-(1-((4-(6-phenyl-1H-imidazo[4,5-g]quinoxalin-7-yl)phenyl)methyl)-4-piperidinyl)-2H-benzimidazol-2-one (an Akt1 and 2 inhibitor; compound 8) killed cancer cells 10-120 times more effectively than normal cells. Thus, CQ is a very effective and cancer-specific chemosensitizer when used in combination with Akt inhibitors.