Unique O-methoxyethyl ribose-DNA chimeric oligonucleotide induces an atypical melanoma differentiation-associated gene 5-dependent induction of type I interferon response.

Antisense oligonucleotides (ASO) containing 2'-O-methoxyethyl ribose (2'-MOE) modifications have been shown to possess both excellent pharmacokinetic properties and robust pharmacological activity in several animal models of human disease. 2'-MOE ASOs are generally well tolerated, displaying minimal to mild proinflammatory effect at doses far exceeding therapeutic doses. Although the vast majority of 2'-MOE ASOs are safe and well tolerated, a small subset of ASOs inducing acute inflammation in mice has been identified. The mechanism for these findings is not clear at this point, but the effects are clearly sequence-specific. One of those ASOs, ISIS 147420, causes a severe inflammatory response atypical of this class of oligonucleotides characterized by induction in interferon-ß (IFN-ß) at 48 h followed by acute transaminitis and extensive hepatocyte apoptosis and necrosis at 72 h. A large number of interferon-stimulated genes were significantly up-regulated in liver as early as 24 h. We speculated that a specific sequence motif might cause ISIS 147420 to be mistaken for viral RNA or DNA, thus triggering an acute innate immune response. ISIS 147420 toxicity was independent of Toll-like receptors, because there was no decrease in IFN-ß in Toll/interleukin-1 receptor-domain-containing adapter-inducing IFN-ß or Myd88-deficient mice. The involvement of cytosolic retinoic acid-inducible gene (RIG)-I-like pattern recognition receptors was also investigated. Pretreatment of mice with melanoma differentiation-associated gene 5 (MDA5) and IFN-ß promoter stimulator-1 ASOs, but not RIG-I or laboratory of genetics and physiology 2 (LGP2) ASOs, prevented the increase in IFN-ß and alanine aminotransferase induced by ISIS 147420. These results revealed a novel mechanism of oligonucleotide-mediated toxicity requiring both MDA5 and IPS-1 and resulting in the activation of the innate immune response.

Modulation of beta-catenin and E-cadherin interaction by Vpu increases human immunodeficiency virus type 1 particle release.

Vpu (viral protein U) is a 17-kDa human immunodeficiency virus type 1 (HIV-1) accessory protein that enhances the release of particles from the surfaces of infected cells. Vpu recruits beta-transducin repeat-containing protein (beta-TrCP) and mediates proteasomal degradation of CD4. By sequestering beta-TrCP away from other cellular substrates, Vpu leads to the stabilization of beta-TrCP substrates such as beta-catenin, IkappaBalpha, ATF4, and Cdc25A, but not of other substrates such as Emi1. This study shows that in addition to stabilizing beta-catenin, Vpu leads to the depression of both total and beta-catenin-associated E-cadherin levels through beta-TrCP-dependent stabilization of the transcriptional repressor Snail. We showed that both downregulation of overall E-cadherin levels and dissociation of E-cadherin from beta-catenin result in enhanced viral release. By contrast, the overexpression of E-cadherin or the prevention of the dissociation of E-cadherin from beta-catenin results in depressed levels of virus release. Since E-cadherin is expressed only in dendritic cells and macrophages, and not in T cells, our data suggest that the HIV-1 vpu gene may have evolved to counteract different restrictions to assembly in different cells.