|ZHU, LILIAN - Oklahoma State University|
|JONES, CLINTON - Oklahoma State University|
Submitted to: Journal of Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/21/2016
Publication Date: 3/1/2017
Citation: Zhu, L., Workman, A.M., Jones, C. 2017. Potential role for a B-catenin coactivator (high mobility group AT-hook 1 protein) during the latency-reactivation cycle of bovine herpesverus 1. Journal of Virology. 91(5):e02132-16.
Interpretive Summary: Bovine herpesvirus 1 (BoHV-1) is a significant viral pathogen of cattle that contributes to bovine respiratory disease, one of the most common and costly diseases affecting the cattle industry. Following acute infection of mucosal linings in the oral, nasal or ocular cavity, BoHV-1 establishes a life-long latency (dormancy) in sensory neurons that reside within trigeminal ganglia (TG). Periodically, the virus will reactivate from latency and cause recurrent disease. The ability of the virus to establish, maintain, and reactivate from latency is crucial for virus transmission in nature. Maintaining life-long latency of BoHV-1 in sensory neurons requires that neurons survive infection and maintain their normal functions. We hypothesized that viral products expressed during latency cooperate with neuronal factors to maintain this symbiotic relationship. Our study revealed that ß-catenin and a coactivator of ß-catenin, high mobility group AT-hook 1 protein (HMGA1), are expressed in a subset of latently infected neurons, but not in neurons of uninfected calves. A viral protein (ORF2) expressed in latently infected neurons interacted with ß-catenin and HMGA1 in transfected cells, which resulted in the activation and nuclear localization of ß-catenin and HMGA1. This interaction correlated with the ability of ORF2 to stimulate the coactivator functions of HMGA1. These findings are significant because the canonical Wnt/ß-catenin signaling pathway promotes cell survival and neurogenesis, suggesting this interaction could enhance neuronal survival and help maintain normal neuronal function in infected neurons, thus promoting the maintenance of latency.
Technical Abstract: The latency-related (LR)-RNA encoded by bovine herpes virus 1 (BoHV-1) is abundantly expressed in latently infected sensory neurons. Although the LR gene encodes several products, ORF2 appears to play a dominant role during the latency-reactivation cycle because a mutant virus containing stop codons at the amino-terminus of ORF2 does not reactivate from latency in calves. We recently discovered that the Wnt/ß-catenin signaling pathway regulates certain aspects of the BoHV-1 latency-reactivation cycle (Liu et al., 2016). In this study, we found that a ß-catenin coactivator, high mobility group AT-hook 1 protein (HMGA1), was readily detected in the nucleus of significantly more TG neurons during latency compared to uninfected calves. Confocal microscopy provided evidence that ORF2 induced nuclear localization of HMGA1 leading to co-localization of ORF2, HMGA1, and ß-catenin in transfected mouse neuroblastoma (Neuro-2A) cells. Co-immunoprecipitation studies demonstrated that ORF2 stably interacted with a complex containing ß-catenin and/or HMGA1. Conversely, another ß-catenin coactivator, CREB binding protein (CBP), was not stably associated with ß-catenin. Furthermore, ORF2 consistently enhanced the ability of HMGA1 to stimulate ß-catenin dependent transcription in transfected Neuro-2A cells. Inserting stop codons at the amino terminus of ORF2, deleting the ORF2 nuclear localization, or mutating all 5 protein kinase A or C phosphorylation sites in ORF2 abolished the ability of ORF2 to stimulate ß-catenin dependent transcription. Considering the canonical Wnt/ß-catenin signaling pathway promotes neurogenesis (synapse formation and remodeling) and inhibits neuro-degeneration, we suggest that interactions between ORF2, HMGA1, and ß-catenin promote the maintenance of latency in sensory neurons.