title: Explant-induced reactivation of herpes simplex virus occurs in neurons expressing nuclear cdk2 and cdk4.
abstract: Herpes simplex virus (HSV) establishes productive (lytic) infections in nonneuronal cells and nonproductive (latent) infections in neurons. It has been proposed that HSV establishes latency because quiescent neurons lack cellular factors required for productive infection. It has been further proposed that these putative factors are induced following neuronal stress, as a requirement for HSV reactivation. To date, the identity of these putative cellular factors remains unknown. We have demonstrated that cyclin-dependent kinase (cdk) 1, 2, or 7 is required for HSV replication in nonneuronal cells. Interestingly, cdks 1 and 2 are not expressed in quiescent neurons but can be induced in stressed neurons. Thus, cdks may be among the cellular proteins required for HSV reactivation whose neuronal expression is differentially regulated during stress. Herein, we determined that neuronal expression of nuclear cdk2, cdk4, and cyclins E and D2 (which activate cdks 2 and 4, respectively) was induced following explant cultivation, a stressful stimulus that induces HSV reactivation. In contrast, neuronal expression of cdk7 and cytoplasmic cdk4 decreased during explant cultivation, whereas cdk3 was detected in the same small percentage of neurons before and after explant cultivation and cdks 1, 5, and 6 were not detected in neuronal cell bodies. HSV-1 reactivated specifically in neurons expressing nuclear cdk2 and cdk4, and an inhibitor specific for cdk2 inhibited HSV-1 reactivation. We conclude that neuronal levels of cdk2 are among the factors that determine the outcome of HSV infections of neurons.
authors.affiliation: Department of Microbiology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA. luis.schang@ualberta.ca
authors.forename: Luis M
authors.initials: LM
authors.lastname: Schang
authors.forename: Andrew
authors.initials: A
authors.lastname: Bantly
authors.forename: Priscilla A
authors.initials: PA
authors.lastname: Schaffer
mesh_terms: D000818:Animals; D042846:CDC2-CDC28 Kinases; D002467:Cell Nucleus / Q000378:metabolism; D046508:Culture Techniques / Q000379:methods; D051357:Cyclin-Dependent Kinase 2; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases / Q000378:metabolism*; D016213:Cyclins / Q000378:metabolism; D007150:Immunohistochemistry; D016849:Keratitis, Herpetic / Q000821:virology; D051379:Mice; D008813:Mice, Inbred ICR; D009474:Neurons / Q000821:virology*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins; D018139:Simplexvirus / Q000254:growth & development*; D012668:Trigeminal Ganglion / Q000166:cytology; D014775:Virus Activation; D017735:Virus Latency
chemical_list: D016213:Cyclins; D011518:Proto-Oncogene Proteins; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495893:Cdk2 protein, mouse; C495902:Cdk4 protein, mouse; D051357:Cyclin-Dependent Kinase 2; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases