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Lawrence SM. Human cytomegalovirus and neonatal infection. CURRENT RESEARCH IN MICROBIAL SCIENCES 2024; 7:100257. [PMID: 39070527 PMCID: PMC11276932 DOI: 10.1016/j.crmicr.2024.100257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/30/2024] Open
Abstract
Human cytomegalovirus is an ancient virus that has co-evolved with humans. It establishes a life-long infection in suspectable individuals for which there is no vaccination or cure. The virus can be transmitted to a developing fetus in seropositive pregnant women, and it is the leading cause of congenital infectious disease. While the majority of infected infants remain asymptomatic at birth, congenital cytomegalovirus infection can lead to substantial long-term neurodevelopmental impairments in survivors, resulting in considerable economic and social hardships. Recent discoveries regarding cytomegalovirus pathophysiology and viral replication cycles might enable the development of innovative diagnostics and therapeutics, including an effective vaccine. This Review will detail our understanding of human cytomegalovirus infection, with an in-depth discussion regarding the viral genome and transcriptome that contributes to its pathophysiology. The neonate's clinical course will also be highlighted, including maternal and neonatal testing, treatment recommendations, and long-term outcomes.
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Affiliation(s)
- Shelley M. Lawrence
- University of Utah, College of Medicine, Department of Pediatrics, Division of Neonatology, Salt Lake City, UT, USA
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Miller MJ, Akter D, Mahmud J, Chan GC. Human cytomegalovirus modulates mTORC1 to redirect mRNA translation within quiescently infected monocytes. J Virol 2024; 98:e0188823. [PMID: 38289104 PMCID: PMC10878035 DOI: 10.1128/jvi.01888-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2023] [Accepted: 12/22/2023] [Indexed: 02/21/2024] Open
Abstract
Human cytomegalovirus (HCMV) utilizes peripheral blood monocytes as a means to systemically disseminate throughout the host. Following viral entry, HCMV stimulates non-canonical Akt signaling leading to the activation of mTORC1 and the subsequent translation of select antiapoptotic proteins within infected monocytes. However, the full extent to which the HCMV-initiated Akt/mTORC1 signaling axis reshapes the monocyte translatome is unclear. We found HCMV entry alone was able to stimulate widescale changes to mRNA translation levels and that inhibition of mTOR, a component of mTORC1, dramatically attenuated HCMV-induced protein synthesis. Although monocytes treated with normal myeloid growth factors also exhibited increased levels of translation, mTOR inhibition had no effect, suggesting HCMV activation of mTOR stimulates the acquisition of a unique translatome within infected monocytes. Indeed, polyribosomal profiling of HCMV-infected monocytes identified distinct prosurvival transcripts that were preferentially loaded with ribosomes when compared to growth factor-treated cells. Sirtuin 1 (SIRT1), a deacetylase that exerts prosurvival effects through regulation of the PI3K/Akt pathway, was found to be highly enriched following HCMV infection in an mTOR-dependent manner. Importantly, SIRT1 inhibition led to the death of HCMV-infected monocytes while having minimal effect on uninfected cells. SIRT1 also supported a positive feedback loop to sustain Akt/mTORC1 signaling following viral entry. Taken together, HCMV profoundly reshapes mRNA translation in an mTOR-dependent manner to enhance the synthesis of select factors necessary for the survival of infected monocytes.IMPORTANCEHuman cytomegalovirus (HCMV) infection is a significant cause of morbidity and mortality among the immunonaïve and immunocompromised. Peripheral blood monocytes are a major cell type responsible for disseminating the virus from the initial site of infection. In order for monocytes to mediate viral spread within the host, HCMV must subvert the naturally short lifespan of these cells. In this study, we performed polysomal profiling analysis, which demonstrated HCMV to globally redirect mRNA translation toward the synthesis of cellular prosurvival factors within infected monocytes. Specifically, HCMV entry into monocytes induced the translation of cellular SIRT1 to generate an antiapoptotic state. Defining the precise mechanisms through which HCMV stimulates survival will provide insight into novel anti-HCMV drugs able to target infected monocytes.
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Affiliation(s)
- Michael J. Miller
- Department of Microbiology and Immunology, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Dilruba Akter
- Department of Microbiology and Immunology, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Jamil Mahmud
- Department of Microbiology and Immunology, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Gary C. Chan
- Department of Microbiology and Immunology, SUNY Upstate Medical University, Syracuse, New York, USA
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Ren Y, Wang A, Zhang B, Ji W, Zhu XX, Lou J, Huang M, Qiu Y, Zhou X. Human cytomegalovirus UL36 inhibits IRF3-dependent immune signaling to counterbalance its immunoenhancement as apoptotic inhibitor. SCIENCE ADVANCES 2023; 9:eadi6586. [PMID: 37792941 PMCID: PMC10550242 DOI: 10.1126/sciadv.adi6586] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2023] [Accepted: 08/31/2023] [Indexed: 10/06/2023]
Abstract
Apoptotic inhibition and immune evasion have particular importance to efficient viral infection, while a dilemma often faced by viruses is that inhibiting apoptosis can up-regulate antiviral immune signaling. Herein, we uncovered that in addition to inhibiting caspase-8/extrinsic apoptosis, human cytomegalovirus (HCMV)-encoded UL36 suppresses interferon regulatory factor 3 (IRF3)-dependent immune signaling by directly targeting IRF3 to abrogate IRF3 interaction with stimulator of interferon genes or TANK-binding kinase 1 and inhibit IRF3 phosphorylation/activation. Although UL36-mediated caspase-8/extrinsic apoptosis inhibition enhances immune signaling, the immunosuppressing activity of UL36 counterbalances this immunoenhancing "side effect" undesirable for virus. Furthermore, we used mutational analyses to show that only the wild-type, but not the UL36 mutant losing either inhibitory activity, is sufficient to support effective HCMV replication in cells, showing the functional importance of the dual inhibition by UL36 for the HCMV life cycle. Together, our findings demonstrate a sophisticated mechanism by which HCMV tightly controls innate immune signaling and extrinsic apoptosis for efficient infection.
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Affiliation(s)
- Yujie Ren
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - An Wang
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Bowen Zhang
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Wenting Ji
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China
- School of Life Sciences, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, China
| | - Xiao-Xu Zhu
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jing Lou
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China
| | - Muhan Huang
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China
| | - Yang Qiu
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xi Zhou
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China
- University of Chinese Academy of Sciences, Beijing 100049, China
- School of Life Sciences, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, China
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Mahmud J, Geiler BW, Biswas J, Miller MJ, Myers JE, Matthews SM, Wass AB, O'Connor CM, Chan GC. Virion-associated US28 rapidly modulates Akt activity to suppress HCMV lytic replication in monocytes. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.05.556359. [PMID: 37732204 PMCID: PMC10508783 DOI: 10.1101/2023.09.05.556359] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/22/2023]
Abstract
Establishing a non-productive quiescent/silent infection within monocytes is essential for spread of human cytomegalovirus (HCMV). Yet, how HCMV establishes a quiescent infection in monocytes remains unclear. US28 is a viral G protein-coupled receptor (GPCR) essential for silent infections within cells of the myeloid lineage. We found virion-associated US28 was rapidly delivered to monocytes, while de novo synthesized US28 was delayed for several days. A recombinant mutant virus lacking US28 (US28Δ) was unable to establish a quiescent infection, resulting in a fully productive lytic replication cycle. Mechanistically, viral entry of US28Δ phosphorylated Akt at both serine 473 (S473) and threonine 308 (T308), which contrasted with the site-specific phosphorylation of Akt at S473 following WT infection. Preventing Akt bi-phosphorylation prevented lytic replication of US28Δ, and ectopic expression of a constitutively phosphorylated Akt variant triggered lytic replication of WT infection. Our data demonstrate that virion-delivered US28 fine-tunes Akt activity to permit HCMV infection to enter a quiescent state following primary infection of monocytes.
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Cheung J, Remiszewski S, Chiang LW, Ahmad E, Pal M, Rahman SA, Nikolovska-Coleska Z, Chan GC. Inhibition of SIRT2 promotes death of human cytomegalovirus-infected peripheral blood monocytes via apoptosis and necroptosis. Antiviral Res 2023; 217:105698. [PMID: 37562606 DOI: 10.1016/j.antiviral.2023.105698] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Revised: 08/02/2023] [Accepted: 08/04/2023] [Indexed: 08/12/2023]
Abstract
Peripheral blood monocytes are the cells predominantly responsible for systemic dissemination of human cytomegalovirus (HCMV) and a significant cause of morbidity and mortality in immunocompromised patients. HCMV establishes a silent/quiescent infection in monocytes, which is defined by the lack of viral replication and lytic gene expression. The absence of replication shields the virus within infected monocytes from the current available antiviral drugs that are designed to suppress active replication. Our previous work has shown that HCMV stimulates a noncanonical phosphorylation of Akt and the subsequent upregulation of a distinct subset of prosurvival proteins in normally short-lived monocytes. In this study, we found that SIRT2 activity is required for the unique activation profile of Akt induced within HCMV-infected monocytes. Importantly, both therapeutic and prophylactic treatment with a novel SIRT2 inhibitor, FLS-379, promoted death of infected monocytes via both the apoptotic and necroptotic cell death pathways. Mechanistically, SIRT2 inhibition reduced expression of Mcl-1, an Akt-dependent antiapoptotic Bcl-2 family member, and enhanced activation of MLKL, the executioner kinase of necroptosis. We have previously reported HCMV to block necroptosis by stimulating cellular autophagy. Here, we additionally demonstrate that inhibition of SIRT2 suppressed Akt-dependent HCMV-induced autophagy leading to necroptosis of infected monocytes. Overall, our data show that SIRT2 inhibition can simultaneously promote death of quiescently infected monocytes by two distinct death pathways, apoptosis and necroptosis, which may be vital for limiting viral dissemination to peripheral organs in immunosuppressed patients.
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Affiliation(s)
- Jennifer Cheung
- Department of Microbiology & Immunology, SUNY Upstate Medical University, Syracuse, NY, 13210, USA
| | - Stacy Remiszewski
- Evrys Bio, LLC, Pennsylvania Biotechnology Center, Doylestown, PA, 18902, USA
| | - Lillian W Chiang
- Evrys Bio, LLC, Pennsylvania Biotechnology Center, Doylestown, PA, 18902, USA
| | - Ejaz Ahmad
- Department of Pathology, University of Michigan Medical School, Ann Arbor, MI, 48109, USA
| | - Mohan Pal
- Department of Pathology, University of Michigan Medical School, Ann Arbor, MI, 48109, USA
| | - Sm Ashikur Rahman
- Department of Pathology, University of Michigan Medical School, Ann Arbor, MI, 48109, USA
| | - Zaneta Nikolovska-Coleska
- Department of Pathology, University of Michigan Medical School, Ann Arbor, MI, 48109, USA; Rogel Cancer Center, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Gary C Chan
- Department of Microbiology & Immunology, SUNY Upstate Medical University, Syracuse, NY, 13210, USA.
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Dual inhibition of innate immunity and apoptosis by human cytomegalovirus protein UL37x1 enables efficient virus replication. Nat Microbiol 2022; 7:1041-1053. [DOI: 10.1038/s41564-022-01136-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Accepted: 04/26/2022] [Indexed: 11/08/2022]
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Abstract
While many viral infections are limited and eventually resolved by the host immune response or by death of the host, other viruses establish long-term relationships with the host by way of a persistent infection, that range from chronic viruses that may be eventually cleared to those that establish life-long persistent or latent infection. Viruses infecting hosts from bacteria to humans establish quiescent infections that must be reactivated to produce progeny. For mammalian viruses, most notably herpesviruses, this quiescent maintenance of viral genomes in the absence of virus replication is referred to as latency. The latent strategy allows the virus to persist quiescently within a single host until conditions indicate a need to reactivate to reach a new host or, to re-seed a reservoir within the host. Here, I review common themes in viral strategies to regulate the latent cycle and reactivate from it ranging from bacteriophage to herpesviruses with a focus on human cytomegalovirus (HCMV). Themes central to herpesvirus latency include, epigenetic repression of viral gene expression and mechanisms to regulate host signaling and survival. Critical to the success of a latent program are mechanisms by which the virus can "sense" fluctuations in host biology (within the host) or environment (outside the host) and make appropriate "decisions" to maintain latency or re-initiate the replicative program. The signals or environments that indicate the establishment of a latent state, the very nature of the latent state, as well as the signals driving reactivation have been topics of intense study from bacteriophage to human viruses, as these questions encompass the height of complexity in virus-host interactions-where the host and the virus coexist.
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Affiliation(s)
- Felicia Goodrum
- Department of Immunobiology, BIO5 Institute, University of Arizona, Tucson, AZ, United States.
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Smith NA, Chan GC, O’Connor CM. Modulation of host cell signaling during cytomegalovirus latency and reactivation. Virol J 2021. [DOI: 10.1186/s12985-021-01674-1
expr 947873540 + 978833141] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/16/2023] Open
Abstract
AbstractBackgroundHuman cytomegalovirus (HCMV) resides latently in cells of the myeloid compartment, including CD34+hematopoietic progenitor cells and circulating monocytes. Healthy hosts maintain the virus latently, and this infection is, for the most part, asymptomatic. However, given the proper external cues, HCMV reactivates from latency, at which point the virus disseminates, causing disease. The viral and cellular factors dictating the balance between these phases of infection are incompletely understood, though a large body of literature support a role for viral-mediated manipulation of host cell signaling.Main bodyTo establish and maintain latency, HCMV has evolved various means by which it usurps host cell factors to alter the cellular environment to its own advantage, including altering host cell signaling cascades. As early as virus entry into myeloid cells, HCMV usurps cellular signaling to change the cellular milieu, and this regulation includes upregulation, as well as downregulation, of different signaling cascades. Indeed, given proper reactivation cues, this signaling is again altered to allow for transactivation of viral lytic genes.ConclusionsHCMV modulation of host cell signaling is not binary, and many of the cellular pathways altered are finely regulated, wherein the slightest modification imparts profound changes to the cellular milieu. It is also evident that viral-mediated cell signaling differs not only between these phases of infection, but also is myeloid cell type specific. Nonetheless, understanding the exact pathways and the means by which HCMV mediates them will undoubtedly provide novel targets for therapeutic intervention.
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Modulation of host cell signaling during cytomegalovirus latency and reactivation. Virol J 2021; 18:207. [PMID: 34663377 PMCID: PMC8524946 DOI: 10.1186/s12985-021-01674-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Accepted: 09/30/2021] [Indexed: 12/15/2022] Open
Abstract
Background Human cytomegalovirus (HCMV) resides latently in cells of the myeloid compartment, including CD34+ hematopoietic progenitor cells and circulating monocytes. Healthy hosts maintain the virus latently, and this infection is, for the most part, asymptomatic. However, given the proper external cues, HCMV reactivates from latency, at which point the virus disseminates, causing disease. The viral and cellular factors dictating the balance between these phases of infection are incompletely understood, though a large body of literature support a role for viral-mediated manipulation of host cell signaling. Main body To establish and maintain latency, HCMV has evolved various means by which it usurps host cell factors to alter the cellular environment to its own advantage, including altering host cell signaling cascades. As early as virus entry into myeloid cells, HCMV usurps cellular signaling to change the cellular milieu, and this regulation includes upregulation, as well as downregulation, of different signaling cascades. Indeed, given proper reactivation cues, this signaling is again altered to allow for transactivation of viral lytic genes. Conclusions HCMV modulation of host cell signaling is not binary, and many of the cellular pathways altered are finely regulated, wherein the slightest modification imparts profound changes to the cellular milieu. It is also evident that viral-mediated cell signaling differs not only between these phases of infection, but also is myeloid cell type specific. Nonetheless, understanding the exact pathways and the means by which HCMV mediates them will undoubtedly provide novel targets for therapeutic intervention.
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Evasion of the Host Immune Response by Betaherpesviruses. Int J Mol Sci 2021; 22:ijms22147503. [PMID: 34299120 PMCID: PMC8306455 DOI: 10.3390/ijms22147503] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Revised: 07/11/2021] [Accepted: 07/12/2021] [Indexed: 02/07/2023] Open
Abstract
The human immune system boasts a diverse array of strategies for recognizing and eradicating invading pathogens. Human betaherpesviruses, a highly prevalent subfamily of viruses, include human cytomegalovirus (HCMV), human herpesvirus (HHV) 6A, HHV-6B, and HHV-7. These viruses have evolved numerous mechanisms for evading the host response. In this review, we will highlight the complex interplay between betaherpesviruses and the human immune response, focusing on protein function. We will explore methods by which the immune system first responds to betaherpesvirus infection as well as mechanisms by which viruses subvert normal cellular functions to evade the immune system and facilitate viral latency, persistence, and reactivation. Lastly, we will briefly discuss recent advances in vaccine technology targeting betaherpesviruses. This review aims to further elucidate the dynamic interactions between betaherpesviruses and the human immune system.
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Human Cytomegalovirus UL7, miR-US5-1, and miR-UL112-3p Inactivation of FOXO3a Protects CD34 + Hematopoietic Progenitor Cells from Apoptosis. mSphere 2021; 6:6/1/e00986-20. [PMID: 33408225 PMCID: PMC7845589 DOI: 10.1128/msphere.00986-20] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Human cytomegalovirus (HCMV) infection of myeloid lineage cells, such as CD34+ hematopoietic progenitor cells (HPCs) or monocytes, results in the upregulation of antiapoptotic cellular proteins that protect the newly infected cells from programmed cell death. The mechanisms used by HCMV to regulate proapoptotic cellular proteins upon infection of CD34+ HPCs have not been fully explored. Here, we show that HCMV utilizes pUL7, a secreted protein that signals through the FLT3 receptor, and miR-US5-1 and miR-UL112-3p to reduce the abundance and activity of the proapoptotic transcription factor FOXO3a at early times after infection of CD34+ HPCs. Regulation of FOXO3a by pUL7, miR-US5-1, and miR-UL112 results in reduced expression of the proapoptotic BCL2L11 transcript and protection of CD34+ HPCs from virus-induced apoptosis. These data highlight the importance of both viral proteins and microRNAs (miRNAs) in protecting CD34+ HPCs from apoptosis at early times postinfection, allowing for the establishment of latency and maintenance of viral genome-containing cells.IMPORTANCE Human cytomegalovirus (HCMV) causes serious disease in immunocompromised individuals and is a significant problem during transplantation. The virus can establish a latent infection in CD34+ hematopoietic progenitor cells (HPCs) and periodically reactivate to cause disease in the absence of an intact immune system. What viral gene products are required for successful establishment of latency is still not fully understood. Here, we show that both a viral protein and viral miRNAs are required to prevent apoptosis after infection of CD34+ HPCs. HCMV pUL7 and miRNAs miR-US5-1 and miR-UL112-3p act to limit the expression and activation of the transcription factor FOXO3a, which in turn reduces expression of proapoptotic gene BCL2L11 and prevents virus-induced apoptosis in CD34+ HPCs.
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Human Cytomegalovirus-Induced Autophagy Prevents Necroptosis of Infected Monocytes. J Virol 2020; 94:JVI.01022-20. [PMID: 32878887 DOI: 10.1128/jvi.01022-20] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2020] [Accepted: 08/21/2020] [Indexed: 12/20/2022] Open
Abstract
Key to the viral dissemination strategy of human cytomegalovirus (HCMV) is the induction of monocyte survival, where monocytes are normally short-lived cells. Autophagy is a cellular process that preserves cellular homeostasis and promotes cellular survival during times of stress. We found that HCMV rapidly induced autophagy within infected monocytes. The early induction of autophagy during HCMV infection was distinctly required for the survival of HCMV-infected monocytes, as repression of autophagosome formation led to cellular death of infected cells but had no effect on the viability of uninfected monocytes. The inhibition of caspases was insufficient to rescue cell viability of autophagy-repressed infected monocytes, suggesting that autophagy was not protecting cells from apoptosis. Accordingly, we found that HCMV blocked the activation of caspase 8, which was maintained in the presence of autophagy inhibitors. Necroptosis is an alternative form of cell death triggered when apoptosis is impeded and is dependent on RIPK3 phosphorylation of MLKL. Although we found that HCMV activated RIP3K upon infection, MLKL was not activated. However, inhibition of autophagy removed the block in RIPK3 phosphorylation of MLKL, suggesting that autophagy was protecting infected monocytes from undergoing necroptosis. Indeed, survival of autophagy-inhibited HCMV-infected monocytes was rescued when MLKL and RIPK3 were suppressed. Taken together, these data indicate that HCMV induces autophagy to prevent necroptotic cell death in order to ensure the survival of infected monocytes and thus facilitate viral dissemination within the host.IMPORTANCE Human cytomegalovirus (HCMV) infection is endemic throughout the world, with a seroprevalence of 40 to 100% depending on geographic location. HCMV infection is generally asymptomatic, but can cause severe inflammatory organ diseases in immunocompromised individuals. The broad array of organ diseases caused by HCMV is directly linked to the systematic spread of the virus mediated by monocytes. Monocytes are naturally programmed to undergo apoptosis, which is rapidly blocked by HCMV to ensure the survival and dissemination of infected monocytes to different organ sites. In this work, we demonstrate infected monocytes also initiate necroptosis as a "trap door" death pathway in response to HCMV subversion of apoptosis. HCMV then activates cellular autophagy as a countermeasure to prevent the execution of necroptosis, thereby promoting the continued survival of infected monocytes. Elucidating the mechanisms by which HCMV stimulates monocyte survival is an important step to the development of novel anti-HCMV drugs that prevent the spread of infected monocytes.
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Human Cytomegalovirus Glycoprotein-Initiated Signaling Mediates the Aberrant Activation of Akt. J Virol 2020; 94:JVI.00167-20. [PMID: 32493823 DOI: 10.1128/jvi.00167-20] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Accepted: 05/27/2020] [Indexed: 11/20/2022] Open
Abstract
Human cytomegalovirus (HCMV) is a major cause of morbidity and mortality among immunocompromised and immunonaive individuals. HCMV-induced signaling initiated during viral entry stimulates a rapid noncanonical activation of Akt to drive the differentiation of short-lived monocytes into long-lived macrophages, which is essential for viral dissemination and persistence. We found that HCMV glycoproteins gB and gH directly bind and activate cellular epidermal growth factor receptor (EGFR) and integrin β1, respectively, to reshape canonical Akt signaling within monocytes. The remodeling of the Akt signaling network was due to the recruitment of nontraditional Akt activators to either the gB- or gH-generated receptor signaling complexes. Phosphoinositide 3-kinase (PI3K) comprised of the p110β catalytic subunit was recruited to the gB/EGFR complex despite p110δ being the primary PI3K isoform found within monocytes. Concomitantly, SH2 domain-containing inositol 5-phosphatase 1 (SHIP1) was recruited to the gH/integrin β1 complex, which is critical to aberrant Akt activation, as SHIP1 diverts PI3K signaling toward a noncanonical pathway. Although integrin β1 was required for SHIP1 recruitment, gB-activated EGFR mediated SHIP1 activation, underscoring the importance of the interplay between gB- and gH-mediated signaling to the unique activation of Akt during HCMV infection. Indeed, SHIP1 activation mediated the increased expression of Mcl-1 and HSP27, two Akt-dependent antiapoptotic proteins specifically upregulated during HCMV infection but not during growth factor treatment. Overall, our data indicate that HCMV glycoproteins gB and gH work in concert to initiate an HCMV-specific signalosome responsible for the atypical activation of Akt required for infected monocyte survival and ultimately viral persistence.IMPORTANCE Human cytomegalovirus (HCMV) infection is endemic throughout the world regardless of socioeconomic conditions and geographic locations with a seroprevalence reaching up to 100% in some developing countries. Although asymptomatic in healthy individuals, HCMV can cause severe multiorgan disease in immunocompromised or immunonaive patients. HCMV disease is a direct consequence of monocyte-mediated systematic spread of the virus following infection. Because monocytes are short-lived cells, HCMV must subvert the natural short life-span of these blood cells by inducing a distinct activation of Akt, a serine/theonine protein kinase. In this work, we demonstrate that HCMV glycoproteins gB and gH work in tandem to reroute classical host cellular receptor signaling to aberrantly activate Akt and drive survival of infected monocytes. Deciphering how HCMV modulates the cellular pathway to induce monocyte survival is important to develop a new class of anti-HCMV drugs that could target and prevent spread of the virus by eliminating infected monocytes.
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Mlera L, Moy M, Maness K, Tran LN, Goodrum FD. The Role of the Human Cytomegalovirus UL133-UL138 Gene Locus in Latency and Reactivation. Viruses 2020; 12:E714. [PMID: 32630219 PMCID: PMC7411667 DOI: 10.3390/v12070714] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Revised: 06/29/2020] [Accepted: 06/29/2020] [Indexed: 12/13/2022] Open
Abstract
Human cytomegalovirus (HCMV) latency, the means by which the virus persists indefinitely in an infected individual, is a major frontier of current research efforts in the field. Towards developing a comprehensive understanding of HCMV latency and its reactivation from latency, viral determinants of latency and reactivation and their host interactions that govern the latent state and reactivation from latency have been identified. The polycistronic UL133-UL138 locus encodes determinants of both latency and reactivation. In this review, we survey the model systems used to investigate latency and new findings from these systems. Particular focus is given to the roles of the UL133, UL135, UL136 and UL138 proteins in regulating viral latency and how their known host interactions contribute to regulating host signaling pathways towards the establishment of or exit from latency. Understanding the mechanisms underlying viral latency and reactivation is important in developing strategies to block reactivation and prevent CMV disease in immunocompromised individuals, such as transplant patients.
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Affiliation(s)
- Luwanika Mlera
- BIO5 Institute, University of Arizona, Tucson, AZ 85719, USA;
| | - Melissa Moy
- Graduate Interdisciplinary Program in Cancer Biology, Tucson, AZ 85719, USA;
| | - Kristen Maness
- Immunobiology Department, University of Arizona, Tucson, AZ 85719, USA; (K.M.); (L.N.T.)
| | - Linh N. Tran
- Immunobiology Department, University of Arizona, Tucson, AZ 85719, USA; (K.M.); (L.N.T.)
| | - Felicia D. Goodrum
- BIO5 Institute, University of Arizona, Tucson, AZ 85719, USA;
- Graduate Interdisciplinary Program in Cancer Biology, Tucson, AZ 85719, USA;
- Immunobiology Department, University of Arizona, Tucson, AZ 85719, USA; (K.M.); (L.N.T.)
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Human Cytomegalovirus Mediates Unique Monocyte-to-Macrophage Differentiation through the PI3K/SHIP1/Akt Signaling Network. Viruses 2020; 12:v12060652. [PMID: 32560319 PMCID: PMC7354488 DOI: 10.3390/v12060652] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Revised: 05/29/2020] [Accepted: 06/09/2020] [Indexed: 12/11/2022] Open
Abstract
Blood monocytes mediate the hematogenous dissemination of human cytomegalovirus (HCMV) in the host. However, monocytes have a short 48-hour (h) lifespan and are not permissive for viral replication. We previously established that HCMV infection drives differentiation of monocytes into long-lived macrophages to mediate viral dissemination, though the mechanism was unclear. Here, we found that HCMV infection promoted monocyte polarization into distinct macrophages by inducing select M1 and M2 differentiation markers and that Akt played a central role in driving differentiation. Akt's upstream positive regulators, PI3K and SHIP1, facilitated the expression of the M1/M2 differentiation markers with p110δ being the predominant PI3K isoform inducing differentiation. Downstream of Akt, M1/M2 differentiation was mediated by caspase 3, whose activity was tightly regulated by Akt in a temporal manner. Overall, this study highlights that HCMV employs the PI3K/SHIP1/Akt pathway to regulate caspase 3 activity and drive monocyte differentiation into unique macrophages, which is critical for viral dissemination.
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Zhu W, Liu S. The role of human cytomegalovirus in atherosclerosis: a systematic review. Acta Biochim Biophys Sin (Shanghai) 2020; 52:339-353. [PMID: 32253424 DOI: 10.1093/abbs/gmaa005] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Revised: 11/05/2019] [Accepted: 01/20/2020] [Indexed: 12/11/2022] Open
Abstract
Atherosclerosis is a progressive vascular disease with increasing morbidity and mortality year by year in modern society. Human cytomegalovirus (HCMV) infection is closely associated with the development of atherosclerosis. HCMV infection may accelerate graft atherosclerosis and the development of transplant vasculopathy in organ transplantation. However, our current understanding of HCMV-associated atherosclerosis remains limited and is mainly based on clinical observations. The underlying mechanism of the involvement of HCMV infection in atherogenesis remains unclear. Here, we summarized current knowledge regarding the multiple influences of HCMV on a diverse range of infected cells, including vascular endothelial cells, vascular smooth muscle cells, monocytes, macrophages, and T cells. In addition, we described potential HCMV-induced molecular mechanisms, such as oxidative stress, endoplasmic reticulum stress, autophagy, lipid metabolism, and miRNA regulation, which are involved in the development of HCMV-associated atherogenesis. Gaining an improved understanding of these mechanisms will facilitate the development of novel and effective therapeutic strategies for the treatment of HCMV-related cardiovascular disease.
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Affiliation(s)
- Wenbo Zhu
- Clinical Research Institute, First Affiliated Hospital, University of South China, Hengyang 421001, China
| | - Shuangquan Liu
- Clinical Laboratory, First Affiliated Hospital, University of South China, Hengyang 421001, China
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Forte E, Zhang Z, Thorp EB, Hummel M. Cytomegalovirus Latency and Reactivation: An Intricate Interplay With the Host Immune Response. Front Cell Infect Microbiol 2020; 10:130. [PMID: 32296651 PMCID: PMC7136410 DOI: 10.3389/fcimb.2020.00130] [Citation(s) in RCA: 113] [Impact Index Per Article: 28.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2019] [Accepted: 03/10/2020] [Indexed: 12/16/2022] Open
Abstract
CMV is an ancient herpesvirus that has co-evolved with its host over millions of years. The 236 kbp genome encodes at least 165 genes, four non-coding RNAs and 14 miRNAs. Of the protein-coding genes, 43-44 are core replication genes common to all herpesviruses, while ~30 are unique to betaherpesviruses. Many CMV genes are involved in evading detection by the host immune response, and others have roles in cell tropism. CMV replicates systemically, and thus, has adapted to various biological niches within the host. Different biological niches may place competing demands on the virus, such that genes that are favorable in some contexts are unfavorable in others. The outcome of infection is dependent on the cell type. In fibroblasts, the virus replicates lytically to produce infectious virus. In other cell types, such as myeloid progenitor cells, there is an initial burst of lytic gene expression, which is subsequently silenced through epigenetic repression, leading to establishment of latency. Latently infected monocytes disseminate the virus to various organs. Latency is established through cell type specific mechanisms of transcriptional silencing. In contrast, reactivation is triggered through pathways activated by inflammation, infection, and injury that are common to many cell types, as well as differentiation of myeloid cells to dendritic cells. Thus, CMV has evolved a complex relationship with the host immune response, in which it exploits cell type specific mechanisms of gene regulation to establish latency and to disseminate infection systemically, and also uses the inflammatory response to infection as an early warning system which allows the virus to escape from situations in which its survival is threatened, either by cellular damage or infection of the host with another pathogen. Spontaneous reactivation induced by cellular aging/damage may explain why extensive expression of lytic genes has been observed in recent studies using highly sensitive transcriptome analyses of cells from latently infected individuals. Recent studies with animal models highlight the potential for harnessing the host immune response to blunt cellular injury induced by organ transplantation, and thus, prevent reactivation of CMV and its sequelae.
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Affiliation(s)
- Eleonora Forte
- Department of Surgery, Comprehensive Transplant Center, Northwestern University Feinberg School of Medicine, Chicago, IL, United States
| | - Zheng Zhang
- Department of Surgery, Comprehensive Transplant Center, Northwestern University Feinberg School of Medicine, Chicago, IL, United States
| | - Edward B. Thorp
- Department of Pathology and Pediatrics, Northwestern University Feinberg School of Medicine, Chicago, IL, United States
| | - Mary Hummel
- Department of Surgery, Comprehensive Transplant Center, Northwestern University Feinberg School of Medicine, Chicago, IL, United States
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Buehler J, Carpenter E, Zeltzer S, Igarashi S, Rak M, Mikell I, Nelson JA, Goodrum F. Host signaling and EGR1 transcriptional control of human cytomegalovirus replication and latency. PLoS Pathog 2019; 15:e1008037. [PMID: 31725811 PMCID: PMC6855412 DOI: 10.1371/journal.ppat.1008037] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2019] [Accepted: 08/21/2019] [Indexed: 12/15/2022] Open
Abstract
Sustained phosphotinositide3-kinase (PI3K) signaling is critical to the maintenance of alpha and beta herpesvirus latency. We have previously shown that the beta-herpesvirus, human cytomegalovirus (CMV), regulates epidermal growth factor receptor (EGFR), upstream of PI3K, to control states of latency and reactivation. How signaling downstream of EGFR is regulated and how this impacts CMV infection and latency is not fully understood. We demonstrate that CMV downregulates EGFR early in the productive infection, which blunts the activation of EGFR and its downstream pathways in response to stimuli. However, CMV infection sustains basal levels of EGFR and downstream pathway activity in the context of latency in CD34+ hematopoietic progenitor cells (HPCs). Inhibition of MEK/ERK, STAT or PI3K/AKT pathways downstream of EGFR increases viral reactivation from latently infected CD34+ HPCs, defining a role for these pathways in latency. We hypothesized that CMV modulation of EGFR signaling might impact viral transcription important to latency. Indeed, EGF-stimulation increased expression of the UL138 latency gene, but not immediate early or early viral genes, suggesting that EGFR signaling promotes latent gene expression. The early growth response-1 (EGR1) transcription factor is induced downstream of EGFR signaling through the MEK/ERK pathway and is important for the maintenance of hematopoietic stemness. We demonstrate that EGR1 binds the viral genome upstream of UL138 and is sufficient to promote UL138 expression. Further, disruption of EGR1 binding upstream of UL138 prevents the establishment of latency in CD34+ HPCs. Our results indicate a model whereby UL138 modulation of EGFR signaling feeds back to promote UL138 gene expression and suppression of replication for latency. By this mechanism, the virus has hardwired itself into host cell biology to sense and respond to changes in homeostatic host cell signaling. Host signaling is important for regulating states of cytomegalovirus (CMV) replication and latency. We have shown that human cytomegalovirus regulates EGFR levels and trafficking and that sustained EGFR or downstream PI3K signaling is a requirement for viral latency. Changes in host signaling have the ability to alter viral and host gene expression to impact the outcome of infection. Here we show that EGFR signaling through MEK/ERK pathway induces the host EGR1 transcription factor that is highly expressed in hematopoietic stem cells and necessary for the maintenance of hematopoietic stemness. Downregulation of EGR1 promotes stem cell mobilization and differentiation, known stimuli for CMV reactivation. We identified functional EGR1 binding sites upstream of the UL138 CMV latency gene and EGR1 stimulated UL138 expression to reinforce the latent infection. Mutant viruses where the regulation of UL138 by EGR1 is disrupted are unable to establish latency in CD34+ HPCs. This study advances our understanding of how host signaling impacts decisions to enter into or exit from latency. The regulation of viral gene expression by host signaling allows the virus to sense and respond to changes in host stress or differentiation.
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Affiliation(s)
- Jason Buehler
- BIO5 Institute, University of Arizona, Tucson, Arizona, United States of America
| | - Ethan Carpenter
- BIO5 Institute, University of Arizona, Tucson, Arizona, United States of America
| | - Sebastian Zeltzer
- BIO5 Institute, University of Arizona, Tucson, Arizona, United States of America
| | - Suzu Igarashi
- BIO5 Institute, University of Arizona, Tucson, Arizona, United States of America
| | - Michael Rak
- BIO5 Institute, University of Arizona, Tucson, Arizona, United States of America
| | - Iliyana Mikell
- Vaccine and Gene Therapy Institute, Oregon Health & Science University, Beaverton, Oregon, United States of America
| | - Jay A. Nelson
- Vaccine and Gene Therapy Institute, Oregon Health & Science University, Beaverton, Oregon, United States of America
| | - Felicia Goodrum
- BIO5 Institute, University of Arizona, Tucson, Arizona, United States of America
- Department of Immunobiology, University of Arizona, Tucson, Arizona, United States of America
- * E-mail:
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Yuan G, Rong L, Liu J, Zhang Z, Hu C, Chen M, Ma L, Zhang YY, Li YP, Zhou Y. Serum‑derived hepatitis C virus can infect human glioblastoma cell line SF268 and activate the PI3K‑Akt pathway. Mol Med Rep 2019; 19:4441-4448. [PMID: 30896873 DOI: 10.3892/mmr.2019.10063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Accepted: 02/08/2019] [Indexed: 11/06/2022] Open
Abstract
Extra‑hepatic manifestations are frequently observed in hepatitis C virus (HCV)‑infected patients; however the underlying mechanisms remain largely unknown. In the present study, the human glioblastoma SF268 cell line (the precise origin of the cell type is not clear) was infected with HCV using HCV‑positive serum, and viral replication was assessed by immunofluorescence, reverse transcription‑polymerase chain reaction (PCR), quantitative PCR and western blotting following infection. HCV core protein and HCV RNA were detected in HCV‑positive serum‑infected SF268 cells at day 4 post‑infection, while no infection was observed in cells exposed to HCV‑negative serum. The mean HCV RNA levels at day 4 post‑infection were up to 5.00 IU/ml log10; however, HCV RNA and immunostaining for core protein were negative when cultured to day 6 or longer. The data suggest that human glioblastoma SF268 cells were transiently infected with HCV. AKT serine/threonine kinase phosphorylation was also detected in HCV‑infected SF268 cells at day 4 post‑infection. To the best of our knowledge, this is the first demonstration that a human glioblastoma cell line can be infected with serum‑derived HCV. The results provide evidence that HCV infection can occur in cells of the central nervous system. Neurological disorder‑associated phosphoinositide 3‑kinase‑AKT signaling pathway was activated in parallel with HCV infection, suggesting that SF268 may serve as an in vitro model for investigating HCV‑nervous system cell interactions.
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Affiliation(s)
- Guosheng Yuan
- Department of Infectious Diseases and Hepatology Unit, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong 510515, P.R. China
| | - Liang Rong
- Institute of Human Virology and Key Laboratory of Tropical Disease Control of Ministry of Education, Zhongshan School of Medicine, Sun Yat‑sen University, Guangzhou, Guangdong 510080, P.R. China
| | - Junwei Liu
- Department of Infectious Diseases and Hepatology Unit, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong 510515, P.R. China
| | - Zhenzhen Zhang
- Institute of Human Virology and Key Laboratory of Tropical Disease Control of Ministry of Education, Zhongshan School of Medicine, Sun Yat‑sen University, Guangzhou, Guangdong 510080, P.R. China
| | - Chengguang Hu
- Department of Infectious Diseases and Hepatology Unit, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong 510515, P.R. China
| | - Mingxiao Chen
- Institute of Human Virology and Key Laboratory of Tropical Disease Control of Ministry of Education, Zhongshan School of Medicine, Sun Yat‑sen University, Guangzhou, Guangdong 510080, P.R. China
| | - Ling Ma
- Institute of Human Virology and Key Laboratory of Tropical Disease Control of Ministry of Education, Zhongshan School of Medicine, Sun Yat‑sen University, Guangzhou, Guangdong 510080, P.R. China
| | | | - Yi-Ping Li
- Institute of Human Virology and Key Laboratory of Tropical Disease Control of Ministry of Education, Zhongshan School of Medicine, Sun Yat‑sen University, Guangzhou, Guangdong 510080, P.R. China
| | - Yuanping Zhou
- Department of Infectious Diseases and Hepatology Unit, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong 510515, P.R. China
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Altman AM, Mahmud J, Nikolovska-Coleska Z, Chan G. HCMV modulation of cellular PI3K/AKT/mTOR signaling: New opportunities for therapeutic intervention? Antiviral Res 2019; 163:82-90. [PMID: 30668978 PMCID: PMC6391997 DOI: 10.1016/j.antiviral.2019.01.009] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2018] [Revised: 01/09/2019] [Accepted: 01/16/2019] [Indexed: 12/15/2022]
Abstract
Human cytomegalovirus (HCMV) remains a major public health burden domestically and abroad. Current approved therapies, including ganciclovir, are only moderately efficacious, with many transplant patients suffering from a variety of side effects. A major impediment to the efficacy of current anti-HCMV drugs is their antiviral effects are restricted to the lytic stage of viral replication. Consequently, the non-lytic stages of the viral lifecycle remain major sources of HCMV infection associated with transplant recipients and ultimately the cause of morbidity and mortality. While work continues on new antivirals that block lytic replication, the dormant stages of HCMV's unique lifecycle need to be concurrently assessed for new therapeutic interventions. In this review, we will examine the role that the PI3K/Akt/mTOR signaling axis plays during the different stages of HCMV's lifecycle, and describe the advantages of targeting this cellular pathway as an antiviral strategy. In particular, we focus on the potential of exploiting the unique modifications HCMV imparts on the PI3K/Akt/mTOR pathway during quiescent infection of monocytes, which serve an essential role in the dissemination strategy of the virus.
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Affiliation(s)
- Aaron M Altman
- Department of Microbiology & Immunology, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | - Jamil Mahmud
- Department of Microbiology & Immunology, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | | | - Gary Chan
- Department of Microbiology & Immunology, SUNY Upstate Medical University, Syracuse, NY 13210, USA.
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HCMV Infection and Apoptosis: How Do Monocytes Survive HCMV Infection? Viruses 2018; 10:v10100533. [PMID: 30274264 PMCID: PMC6213175 DOI: 10.3390/v10100533] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Revised: 09/10/2018] [Accepted: 09/26/2018] [Indexed: 12/11/2022] Open
Abstract
Human cytomegalovirus (HCMV) infection of peripheral blood monocytes plays a key role in the hematogenous dissemination of the virus to multiple organ systems following primary infection or reactivation of latent virus in the bone marrow. Monocytes have a short life span of 1⁻3 days in circulation; thus, HCMV must alter their survival and differentiation to utilize these cells and their differentiated counterparts-macrophages-for dissemination and long term viral persistence. Because monocytes are not initially permissive for viral gene expression and replication, HCMV must control host-derived factors early during infection to prevent apoptosis or programmed cell death prior to viral induced differentiation into naturally long-lived macrophages. This review provides a short overview of HCMV infection of monocytes and describes how HCMV has evolved to utilize host cell anti-apoptotic pathways to allow infected monocytes to bridge the 48⁻72 h viability gate so that differentiation into a long term stable mature cell can occur. Because viral gene expression is delayed in monocytes following initial infection and only occurs (begins around two to three weeks post infection in our model) following what appears to be complete differentiation into mature macrophages or dendritic cells, or both; virally-encoded anti-apoptotic gene products cannot initially control long term infected cell survival. Anti-apoptotic viral genes are discussed in the second section of this review and we argue they would play an important role in long term macrophage or dendritic cell survival following infection-induced differentiation.
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22
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Collins-McMillen D, Buehler J, Peppenelli M, Goodrum F. Molecular Determinants and the Regulation of Human Cytomegalovirus Latency and Reactivation. Viruses 2018; 10:E444. [PMID: 30127257 PMCID: PMC6116278 DOI: 10.3390/v10080444] [Citation(s) in RCA: 82] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Revised: 08/16/2018] [Accepted: 08/17/2018] [Indexed: 02/06/2023] Open
Abstract
Human cytomegalovirus (HCMV) is a beta herpesvirus that establishes a life-long persistence in the host, like all herpesviruses, by way of a latent infection. During latency, viral genomes are maintained in a quieted state. Virus replication can be reactivated from latency in response to changes in cellular signaling caused by stress or differentiation. The past decade has brought great insights into the molecular basis of HCMV latency. Here, we review the complex persistence of HCMV with consideration of latent reservoirs, viral determinants and their host interactions, and host signaling and the control of cellular and viral gene expression that contributes to the establishment of and reactivation from latency.
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Affiliation(s)
| | - Jason Buehler
- BIO5 Institute, University of Arizona, Tucson, AZ 85721, USA.
| | | | - Felicia Goodrum
- BIO5 Institute, University of Arizona, Tucson, AZ 85721, USA.
- Department of Immunobiology, University of Arizona, Tucson, AZ 85721, USA.
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Aberrant regulation of the Akt signaling network by human cytomegalovirus allows for targeting of infected monocytes. Antiviral Res 2018; 158:13-24. [PMID: 30055197 DOI: 10.1016/j.antiviral.2018.07.015] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Revised: 07/17/2018] [Accepted: 07/20/2018] [Indexed: 12/18/2022]
Abstract
Primary peripheral blood monocytes are responsible for the hematogenous dissemination of human cytomegalovirus (HCMV) following a primary infection. In order to facilitate viral spread, HCMV extends the naturally short 48-h lifespan of monocytes by stimulating a non-canonical activation of Akt during viral entry, which leads to the increased expression of a specific subset of antiapoptotic proteins. In this study, global analysis of the Akt signaling network showed HCMV induced a more robust activation of the entire network when compared to normal myeloid growth factors. Furthermore, we found a unique interplay between HCMV-activated Akt and the stress response transcription heat shock factor 1 (HSF1) that allowed for the synthesis of both cap- and internal ribosome entry site (IRES)-containing antiapoptotic mRNAs such as myeloid cell leukemia-1 (Mcl-1) and X-linked inhibitor of apoptosis (XIAP), respectively. As generally a switch from cap-dependent to IRES-mediated translation occurs during cellular stress, the ability of HCMV to concurrently drive both types of translation produces a distinct milieu of prosurvival proteins needed for the viability of infected monocytes. Indeed, we found inhibition of XIAP led to death of ∼99% of HCMV-infected monocytes while having minimal effect on the viability of uninfected cells. Taken together, these data indicate that the aberrant activation of the Akt network by HCMV induces the upregulation of a unique subset of antiapoptotic proteins specifically required for the survival of infected monocytes. Consequently, our study highlights the possibility of exploiting these virus-induced changes to prevent viral spread in immunocompromised patients at high-risk for HCMV exposure.
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A Abdullah A, Abdullah R, A Nazariah Z, N Balakrishnan K, Firdaus J Abdullah F, A Bala J, Mohd-Lila MA. Cyclophilin A as a target in the treatment of cytomegalovirus infections. Antivir Chem Chemother 2018; 26:2040206618811413. [PMID: 30449131 PMCID: PMC6243413 DOI: 10.1177/2040206618811413] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Accepted: 10/12/2018] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND Viruses are obligate parasites that depend on the cellular machinery of the host to regenerate and manufacture their proteins. Most antiviral drugs on the market today target viral proteins. However, the more recent strategies involve targeting the host cell proteins or pathways that mediate viral replication. This new approach would be effective for most viruses while minimizing drug resistance and toxicity. METHODS Cytomegalovirus replication, latency, and immune response are mediated by the intermediate early protein 2, the main protein that determines the effectiveness of drugs in cytomegalovirus inhibition. This review explains how intermediate early protein 2 can modify the action of cyclosporin A, an immunosuppressive, and antiviral drug. It also links all the pathways mediated by cyclosporin A, cytomegalovirus replication, and its encoded proteins. RESULTS Intermediate early protein 2 can influence the cellular cyclophilin A pathway, affecting cyclosporin A as a mediator of viral replication or anti-cytomegalovirus drug. CONCLUSION Cyclosporin A has a dual function in cytomegalovirus pathogenesis. It has the immunosuppressive effect that establishes virus replication through the inhibition of T-cell function. It also has an anti-cytomegalovirus effect mediated by intermediate early protein 2. Both of these functions involve cyclophilin A pathway.
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Affiliation(s)
- Ashwaq A Abdullah
- 1 Institute of Bioscience, University Putra Malaysia, Serdang, Selangor D.E, Malaysia
- 2 Department of Microbiology, Faculty of Applied Science, Taiz University, Taiz, Yemen
| | - Rasedee Abdullah
- 1 Institute of Bioscience, University Putra Malaysia, Serdang, Selangor D.E, Malaysia
- 3 Department of Veterinary Laboratory Diagnosis, Universiti Putra Malaysia, Serdang, Selangor D.E, Malaysia
| | - Zeenathul A Nazariah
- 1 Institute of Bioscience, University Putra Malaysia, Serdang, Selangor D.E, Malaysia
- 4 Department of Pathology and Microbiology, Universiti Putra Malaysia, Serdang, Selangor D.E, Malaysia
| | - Krishnan N Balakrishnan
- 4 Department of Pathology and Microbiology, Universiti Putra Malaysia, Serdang, Selangor D.E, Malaysia
| | - Faez Firdaus J Abdullah
- 5 Department of Veterinary Clinical Studies, Faculty of Veterinary Medicine, Universiti Putra Malaysia, Serdang, Selangor D.E, Malaysia
| | - Jamilu A Bala
- 4 Department of Pathology and Microbiology, Universiti Putra Malaysia, Serdang, Selangor D.E, Malaysia
- 6 Department of Medical Laboratory Science, Faculty of Allied Health Sciences, Bayero University Kano, Kano, Nigeria
| | - Mohd-Azmi Mohd-Lila
- 1 Institute of Bioscience, University Putra Malaysia, Serdang, Selangor D.E, Malaysia
- 4 Department of Pathology and Microbiology, Universiti Putra Malaysia, Serdang, Selangor D.E, Malaysia
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Duran A, Valero N, Mosquera J, Fuenmayor E, Alvarez-Mon M. Gefitinib and pyrrolidine dithiocarbamate decrease viral replication and cytokine production in dengue virus infected human monocyte cultures. Life Sci 2017; 191:180-185. [PMID: 29055802 DOI: 10.1016/j.lfs.2017.10.027] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2017] [Revised: 10/07/2017] [Accepted: 10/17/2017] [Indexed: 02/06/2023]
Abstract
AIMS The epidermal growth factor receptor (EGFR) and nucleotide-binding and oligomerization-domain containing 2 (NOD2) are important in cancer and in microbial recognition, respectively. These molecules trigger intracellular signaling pathways inducing the expression of inflammatory genes by NF-kB translocation. Gefitinib (GBTC) and pyrrolidine dithiocarbamate (PDTC) are capable of inhibiting EGFR/NOD2 and NF-kB, respectively. In earlier stages of dengue virus (DENV) infection, monocytes are capable of sustaining viral replication and increasing cytokine production, suggesting that monocyte/macrophages play an important role in early DENV replication. GBTC and PDTC have not been used to modify the pathogenesis of DENV in infected cells. This study was aimed to determine the effect of GBTC and PDTC on viral replication and cytokine production in DENV serotype 2 (DENV2)-infected human monocyte cultures. MAIN METHODS GBTC and PDTC were used to inhibit EGFR/NOD2 and NF-kB, respectively. Cytokine production was measured by ELISA and viral replication by plaque forming unit assay. KEY FINDINGS Increased DENV2 replication and anti-viral cytokine production (IFN-α/β, TNF-α, IL-12 and IL-18) in infected cultures were found. These parameters were decreased after EGFR/NOD2 or NF-kB inhibitions. SIGNIFICANCE The inhibitory effects of GBTC and PDTC on viral replication and cytokine production can be beneficial in the treatment of patients infected by dengue and suggest a possible role of EGFR/NOD2 receptors and NF-kB in dengue pathogenesis.
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Affiliation(s)
- Anyelo Duran
- Instituto de Investigaciones Clínicas "Dr. Américo Negrette", Facultad de Medicina, Universidad del Zulia, Maracaibo, Venezuela; Cátedra de Bioquímica General, Escuela de Bioanálisis, Facultad de Medicina, Universidad del Zulia, Maracaibo, Venezuela; Sociedad Venezolana de Microbiología, Venezuela
| | - Nereida Valero
- Instituto de Investigaciones Clínicas "Dr. Américo Negrette", Facultad de Medicina, Universidad del Zulia, Maracaibo, Venezuela; Sociedad Venezolana de Microbiología, Venezuela
| | - Jesús Mosquera
- Instituto de Investigaciones Clínicas "Dr. Américo Negrette", Facultad de Medicina, Universidad del Zulia, Maracaibo, Venezuela.
| | - Edgard Fuenmayor
- Instituto de Investigaciones Clínicas "Dr. Américo Negrette", Facultad de Medicina, Universidad del Zulia, Maracaibo, Venezuela
| | - Melchor Alvarez-Mon
- Servicio de Enfermedades del Sistema Inmune y Oncología, Hospital Universitario "Príncipe de Asturias", Universidad de Alcalá, Madrid, Spain
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Ho J, Moyes DL, Tavassoli M, Naglik JR. The Role of ErbB Receptors in Infection. Trends Microbiol 2017; 25:942-952. [PMID: 28522156 PMCID: PMC7126822 DOI: 10.1016/j.tim.2017.04.009] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2017] [Revised: 04/11/2017] [Accepted: 04/24/2017] [Indexed: 01/18/2023]
Abstract
Members of the epidermal growth factor receptor family (ErbB family) possess a wide distribution and diverse functions ranging from cellular growth to migration and apoptosis. Though highly implicated in a variety of cancers, their involvement in infectious disease is less recognised. A growing body of evidence now highlights the importance of the ErbB family in a variety of infections. Their role as growth factor receptors, along with other characteristics, such as surface expression and continuous intracellular trafficking, make this receptor family ideally placed for exploitation by pathogens. Herein, we review our current understanding of the role of the ErbB family in the context of infectious disease, exploring the mechanisms that govern pathogen exploitation of this system. A wide and diverse variety of microbes have each evolved distinct mechanisms to exploit ErbB receptors, highlighting this receptor kinase family as a critical factor in initiation and maintenance of pathogen infections. ErbB family members are utilised by pathogens attempting to gain cellular entry, subvert immune responses, and manipulate the cell cycle of infected host cells. These events support and are necessary for pathogen persistence. Pathogen-mediated ErbB-exploitation may contribute to cellular transformation and oncogenesis in a variety of cancers. The use of existing FDA-approved drugs that target ErbB receptors and associated signalling components may offer potential future therapies against infection.
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Affiliation(s)
- Jemima Ho
- Mucosal & Salivary Biology Division, Dental Institute, King's College London SE1 1UL, UK.
| | - David L Moyes
- Centre for Host Microbiome interactions, Mucosal & Salivary Biology Division, Dental Institute, King's College London SE1 1UL, UK
| | - Mahvash Tavassoli
- Department of Molecular Oncology, Mucosal & Salivary Biology Division, Dental Institute, King's College London SE1 1UL, UK
| | - Julian R Naglik
- Mucosal & Salivary Biology Division, Dental Institute, King's College London SE1 1UL, UK
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McMichael AJ, Picker LJ. Unusual antigen presentation offers new insight into HIV vaccine design. Curr Opin Immunol 2017; 46:75-81. [PMID: 28505602 DOI: 10.1016/j.coi.2017.04.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2016] [Revised: 03/21/2017] [Accepted: 04/17/2017] [Indexed: 11/29/2022]
Abstract
Recent findings with a rhesus monkey cytomegalovirus based simian immunodeficiency virus vaccine have identified strong CD8+ T cell responses that are restricted by MHC-E. Also mycobacteria specific CD8+ T cells, that are MHC-E restricted, have been identified. MHC-E therefore can present a wide range of epitope peptides to CD8+ T cells, alongside its well defined role in presenting a conserved MHC-class I signal peptide to the NKG2A/C-CD94 receptor on natural killer cells. Here we explore the antigen processing pathways involved in these atypical T cell responses.
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Affiliation(s)
- Andrew J McMichael
- Nuffield Deparment of Medicine, Oxford University, Old Road Campus, Oxford OX37FZ, UK.
| | - Louis J Picker
- Vaccine and Gene Therapy Institute, Oregon Health & Science University, 505 NW 185th Avenue, Beaverton, OR 97006-3448, United States
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Arend KC, Lenarcic EM, Vincent HA, Rashid N, Lazear E, McDonald IM, Gilbert TSK, East MP, Herring LE, Johnson GL, Graves LM, Moorman NJ. Kinome Profiling Identifies Druggable Targets for Novel Human Cytomegalovirus (HCMV) Antivirals. Mol Cell Proteomics 2017; 16:S263-S276. [PMID: 28237943 PMCID: PMC5393402 DOI: 10.1074/mcp.m116.065375] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Revised: 02/23/2017] [Indexed: 11/06/2022] Open
Abstract
Human cytomegalovirus (HCMV) is a significant cause of disease in immune-compromised adults and immune naïve newborns. No vaccine exists to prevent HCMV infection, and current antiviral therapies have toxic side effects that limit the duration and intensity of their use. There is thus an urgent need for new strategies to treat HCMV infection. Repurposing existing drugs as antivirals is an attractive approach to limit the time and cost of new antiviral drug development. Virus-induced changes in infected cells are often driven by changes in cellular kinase activity, which led us to hypothesize that defining the complement of kinases (the kinome), whose abundance or expression is altered during infection would identify existing kinase inhibitors that could be repurposed as new antivirals. To this end, we applied a kinase capture technique, multiplexed kinase inhibitor bead-mass spectrometry (MIB-MS) kinome, to quantitatively measure perturbations in >240 cellular kinases simultaneously in cells infected with a laboratory-adapted (AD169) or clinical (TB40E) HCMV strain. MIB-MS profiling identified time-dependent increases and decreases in MIB binding of multiple kinases including cell cycle kinases, receptor tyrosine kinases, and mitotic kinases. Based on the kinome data, we tested the antiviral effects of kinase inhibitors and other compounds, several of which are in clinical use or development. Using a novel flow cytometry-based assay and a fluorescent reporter virus we identified three compounds that inhibited HCMV replication with IC50 values of <1 μm, and at doses that were not toxic to uninfected cells. The most potent inhibitor of HCMV replication was OTSSP167 (IC50 <1.2 nm), a MELK inhibitor, blocked HCMV early gene expression and viral DNA accumulation, resulting in a >3 log decrease in virus replication. These results show the utility of MIB-MS kinome profiling for identifying existing kinase inhibitors that can potentially be repurposed as novel antiviral drugs.
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Affiliation(s)
- Kyle C Arend
- From the ‡Department of Microbiology & Immunology
- ¶Lineberger Comprehensive Cancer Center
| | - Erik M Lenarcic
- From the ‡Department of Microbiology & Immunology
- ¶Lineberger Comprehensive Cancer Center
| | - Heather A Vincent
- From the ‡Department of Microbiology & Immunology
- ¶Lineberger Comprehensive Cancer Center
| | - Naim Rashid
- ¶Lineberger Comprehensive Cancer Center
- ‖Department of Biostatistics
| | - Eric Lazear
- From the ‡Department of Microbiology & Immunology
- ¶Lineberger Comprehensive Cancer Center
| | | | | | | | - Laura E Herring
- §Department of Pharmacology
- **UNC Michael Hooker Proteomics Core Facility University of North Carolina, Chapel Hill, 27599 North Carolina
| | | | - Lee M Graves
- §Department of Pharmacology
- **UNC Michael Hooker Proteomics Core Facility University of North Carolina, Chapel Hill, 27599 North Carolina
| | - Nathaniel J Moorman
- From the ‡Department of Microbiology & Immunology,
- ¶Lineberger Comprehensive Cancer Center
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29
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Adler B, Sattler C, Adler H. Herpesviruses and Their Host Cells: A Successful Liaison. Trends Microbiol 2017; 25:229-241. [DOI: 10.1016/j.tim.2016.11.009] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Revised: 11/08/2016] [Accepted: 11/15/2016] [Indexed: 12/11/2022]
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Kew V, Wills M, Reeves M. HCMV activation of ERK-MAPK drives a multi-factorial response promoting the survival of infected myeloid progenitors. JOURNAL OF MOLECULAR BIOCHEMISTRY 2017; 6:13-25. [PMID: 28491825 PMCID: PMC5421601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Viral binding and entry provides the first trigger of a cell death response and thus how human cytomegalovirus (HCMV) evades this - particularly during latent infection where a very limited pattern of gene expression is observed - is less well understood. It has been demonstrated that the activation of cellular signalling pathways upon virus binding promotes the survival of latently infected cells by the activation of cell encoded anti-apoptotic responses. In CD34+ cells, a major site of HCMV latency, ERK signalling is important for survival and we now show that the activation of this pathway impacts on multiple aspects of cell death pathways. The data illustrate that HCMV infection triggers activation of pro-apoptotic Bak which is then countered through multiple ERK-dependent functions. Specifically, ERK promotes ELK1 mediated transcription of the key survival molecule MCL-1, along with a concomitant decrease of the pro-apoptotic BIM and PUMA proteins. Finally, we show that the elimination of ELK-1 from CD34+ cells results in elevated Bak activation in response to viral infection, resulting in cell death. Taken together, these data begin to shed light on the poly-functional response elicited by HCMV via ERK-MAPK to promote cell survival.
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Affiliation(s)
- Verity Kew
- Department of Medicine, Addenbrooke’s Hospital, Cambridge, UK
| | - Mark Wills
- Department of Medicine, Addenbrooke’s Hospital, Cambridge, UK
| | - Matthew Reeves
- UCL Institute of Immunity & Transplantation, Royal Free Hospital, London, UK
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31
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Burrer CM, Auburn H, Wang X, Luo J, Abulwerdi FA, Nikolovska-Coleska Z, Chan GC. Mcl-1 small-molecule inhibitors encapsulated into nanoparticles exhibit increased killing efficacy towards HCMV-infected monocytes. Antiviral Res 2016; 138:40-46. [PMID: 27914937 DOI: 10.1016/j.antiviral.2016.11.027] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Revised: 11/25/2016] [Accepted: 11/26/2016] [Indexed: 11/26/2022]
Abstract
Human cytomegalovirus (HCMV) spreads and establishes a persistent infection within a host by stimulating the survival of carrier myeloid cells via the upregulation of Mcl-1, an antiapoptotic member of the Bcl-2 family of proteins. However, the lack of potent Mcl-1-specific inhibitors and a targetable delivery system has limited the ability to exploit Mcl-1 as a therapeutic strategy to eliminate HCMV-infected monocytes. In this study, we found a lead compound from a novel class of Mcl-1 small-molecule inhibitors rapidly induced death of HCMV-infected monocytes. Moreover, encapsulation of Mcl-1 antagonists into myeloid cell-targeting nanoparticles was able to selectively increase the delivery of inhibitors into HCMV-activated monocytes, thereby amplifying their potency. Our study demonstrates the potential use of nanotechnology to target Mcl-1 small-molecule inhibitors to HCMV-infected monocytes.
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Affiliation(s)
- Christine M Burrer
- Department of Microbiology & Immunology, SUNY Upstate Medical University, Syracuse, NY 13210, United States
| | - Helen Auburn
- Department of Microbiology & Immunology, SUNY Upstate Medical University, Syracuse, NY 13210, United States
| | - Xu Wang
- Department of Pharmacology, SUNY Upstate Medical University, Syracuse, NY 13210, United States
| | - Juntao Luo
- Department of Pharmacology, SUNY Upstate Medical University, Syracuse, NY 13210, United States
| | - Fardokht A Abulwerdi
- Department of Pathology, University of Michigan, Ann Arbor, MI 48109, United States
| | | | - Gary C Chan
- Department of Microbiology & Immunology, SUNY Upstate Medical University, Syracuse, NY 13210, United States.
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Cell Surface THY-1 Contributes to Human Cytomegalovirus Entry via a Macropinocytosis-Like Process. J Virol 2016; 90:9766-9781. [PMID: 27558416 DOI: 10.1128/jvi.01092-16] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2016] [Accepted: 07/23/2016] [Indexed: 12/14/2022] Open
Abstract
Previously we showed that THY-1 has a critical role in the initial stage of infection of certain cell types with human cytomegalovirus (HCMV) and that THY-1 is important for HCMV-mediated activation of phosphatidylinositol 3-kinase (PI3K)/Akt during virus entry. THY-1 is known to interact with integrins and is a major cargo protein of clathrin-independent endocytic vesicles. Since macropinocytosis involves integrin signaling, is PI3K/Akt dependent, and is a clathrin-independent endocytic process, we determined whether THY-1 has a role in HCMV entry by macropinocytosis. Using electron microscopy in two cell lines that support HCMV infection in a THY-1-dependent manner, we found that HCMV enters these cells by a macropinocytosis-like process. THY-1 associated with HCMV virions on the cell surface and colocalized with virus inside macropinosomes. 5-(N-Ethyl-N-isopropyl)amiloride (EIPA) and soluble THY-1 blocked HCMV infection in the cell lines by ≥80% and 60%, respectively. HCMV entry into the cells triggered increased influx of extracellular fluid, a marker of macropinocytosis, and this increased fluid uptake was inhibited by EIPA and by soluble THY-1. Blocking actin depolymerization, Na+/H+ exchange, PI3K, and Pak1 kinase, which are critical for macropinocytosis, impaired HCMV infection. Neither internalized HCMV virions nor THY-1 in virus-infected cells colocalized with transferrin as determined by confocal microscopy, indicating that clathrin-mediated endocytosis was not involved in THY-1-associated virus entry. These results suggest that HCMV has adapted to utilize THY-1, a cargo protein of clathrin-independent endocytotic vesicles, to facilitate efficient entry into certain cell types by a macropinocytosis-like process. IMPORTANCE Human cytomegalovirus (HCMV) infects over half of the population and is the most common infectious cause of birth defects. The virus is the most important infection occurring in transplant recipients. The mechanism of how HCMV enters cells is controversial. In this study, we show that THY-1, a cell surface protein that is critical for the early stage of entry of HCMV into certain cell types, contributes to virus entry by macropinocytosis. Our findings suggest that HCMV has adapted to utilize THY-1 to facilitate entry of HCMV into macropinosomes in certain cell types. Further knowledge about the mechanism of HCMV entry into cells may facilitate the development of novel inhibitors of virus infection.
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Abstract
Herpesviruses have evolved exquisite virus-host interactions that co-opt or evade a number of host pathways to enable the viruses to persist. Persistence of human cytomegalovirus (CMV), the prototypical betaherpesvirus, is particularly complex in the host organism. Depending on host physiology and the cell types infected, CMV persistence comprises latent, chronic, and productive states that may occur concurrently. Viral latency is a central strategy by which herpesviruses ensure their lifelong persistence. Although much remains to be defined about the virus-host interactions important to CMV latency, it is clear that checkpoints composed of viral and cellular factors exist to either maintain a latent state or initiate productive replication in response to host cues. CMV offers a rich platform for defining the virus-host interactions and understanding the host biology important to viral latency. This review describes current understanding of the virus-host interactions that contribute to viral latency and reactivation.
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Affiliation(s)
- Felicia Goodrum
- Department of Immunobiology, BIO5 Institute, University of Arizona, Tucson, Arizona 85721;
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Human Cytomegalovirus Induces an Atypical Activation of Akt To Stimulate the Survival of Short-Lived Monocytes. J Virol 2016; 90:6443-6452. [PMID: 27147739 DOI: 10.1128/jvi.00214-16] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Accepted: 04/26/2016] [Indexed: 02/02/2023] Open
Abstract
UNLABELLED Human cytomegalovirus (HCMV) is a pervasive herpesvirus responsible for significant morbidity and mortality among immunodeficient/naive hosts. Following a primary HCMV infection, circulating blood monocytes mediate the systemic spread of the virus. Extending the short 48-h life span of monocytes is critical to the viral dissemination process, as these blood-borne cells are nonpermissive for virus replication until they are fully differentiated into macrophages. Here, we show that HCMV glycoprotein gB binding to cellular epidermal growth factor receptor (EGFR) during HCMV entry initiated a rapid (within 15 min) activation of the apoptosis suppressor Akt, which was maintained through 72 h. The virus-induced activation of Akt was more robust than that with the normal myeloid growth factor macrophage colony-stimulating factor (M-CSF) and was essential for infected monocytes to bypass the 48-h viability checkpoint. Activation of phosphoinositide 3-kinase (PI3K) following EGFR engagement by HCMV mediated the phosphorylation of Akt. Moreover, HCMV entry drove a switch away from the PI3K p110δ isoform, which was required for the viability of uninfected monocytes, to the p110β isoform in order to facilitate the Akt-dependent prosurvival state within infected cells. Simultaneously, in contrast to M-CSF, HCMV promoted a rapid increase in SH2 domain-containing inositol 5-phosphatase 1 (SHIP1) expression, leading to signaling through a noncanonical Akt activation pathway. To ensure maximum Akt activity, HCMV also induced an early phosphorylation-dependent inactivation of the negative regulator phosphatase and tensin homolog. Overall, our data indicate that HCMV hijacks the upstream Akt signaling network to induce a nontraditional activation of Akt and subsequently a prosurvival decision at the 48-h cell fate checkpoint, a vital step for HCMV's dissemination and persistence strategy. IMPORTANCE HCMV is found throughout the world with a prevalence of 55 to 100% within the human population. HCMV infection is generally asymptomatic in immunocompetent or naive individuals but is a significant cause of morbidity and mortality among the immunocompromised. Widespread organ inflammation is associated with symptomatic infections, which is a direct consequence of the viral dissemination strategy. Inflammatory peripheral blood monocytes facilitate the spread of HCMV. However, HCMV must subvert the naturally short life span of monocytes. In this work, we demonstrate that HCMV induces the activation of Akt, an antiapoptotic protein, in a manner distinct from that of normal myeloid growth factors. Moreover, we decipher how HCMV dysregulates the upstream Akt signaling network during viral entry to promote an Akt-dependent prosurvival state following infection. Delineation of the virus-specific mechanisms that regulate cellular prosurvival pathways in order to drive the survival of HCMV-infected monocytes is important to identifying new anti-HCMV therapeutic targets.
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