Granzyme M targets host cell hnRNP K that is essential for human cytomegalovirus replication

• Published in: Cell death and differentiation Vol. 20; no. 3; pp. 419 - 429
• Main Authors: van Domselaar, R, de Poot, S A H, Remmerswaal, E B M, Lai, K W, ten Berge, I J M, Bovenschen, N
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.03.2013; Nature Publishing Group
• Subjects: 631/250/1619; 692/699/255/2514; Animals; Apoptosis; Biochemistry; Biomedical and Life Sciences; CD8 antigen; CD8-Positive T-Lymphocytes - immunology; CD8-Positive T-Lymphocytes - metabolism; Cell Biology; Cell Cycle Analysis; Cell death; Cell Line; Congenital defects; Congenital diseases; Cytomegalovirus; Cytomegalovirus - physiology; Cytomegalovirus Infections - virology; Cytotoxicity; Data processing; Drug resistance; endopeptidase; Granzymes - metabolism; HEK293 Cells; HeLa Cells; Heterogeneous-Nuclear Ribonucleoprotein K - antagonists & inhibitors; Heterogeneous-Nuclear Ribonucleoprotein K - genetics; Heterogeneous-Nuclear Ribonucleoprotein K - metabolism; Human cytomegalovirus; Humans; IE2 protein; Immediate-Early Proteins - genetics; Immediate-Early Proteins - metabolism; Immunocompromised hosts; Infection; Infections; Jurkat Cells; Kidney transplants; Latent infection; Life Sciences; Lymphocytes; Lymphocytes T; Mice; mRNA; Murine cytomegalovirus; Mutagenesis; Original Paper; Physiology; Protein expression; Proteins; Replication; ribonucleoprotein K; RNA - metabolism; RNA Interference; RNA, Messenger - metabolism; RNA, Small Interfering - metabolism; Serine proteinase; Stem Cells; T-Lymphocytes, Cytotoxic - immunology; T-Lymphocytes, Cytotoxic - metabolism; Trans-Activators - genetics; Trans-Activators - metabolism; Virus Replication; Viruses; Netherlands; cytotoxic lymphocyte; cytomegalovirus; granzyme M; hnRNP K; transplantation
• ISSN: 1350-9047; 1476-5403
• DOI: 10.1038/cdd.2012.132

Human cytomegalovirus (HCMV) is the most frequent viral cause of congenital defects and HCMV infection in immunocompromised patients may trigger devastating disease. Cytotoxic lymphocytes control HCMV by releasing granzymes towards virus-infected cells. In mice, granzyme M (GrM) has a physiological role in controlling murine CMV infection. However, the underlying mechanism remains poorly understood. In this study, we showed that human GrM was expressed by HCMV-specific CD8 + T cells both in latently infected healthy individuals and in transplant patients during primary HCMV infection. We identified host cell heterogeneous nuclear ribonucleoprotein K (hnRNP K) as a physiological GrM substrate. GrM most efficiently cleaved hnRNP K in the presence of RNA at multiple sites, thereby likely destroying hnRNP K function. Host cell hnRNP K was essential for HCMV replication not only by promoting viability of HCMV-infected cells but predominantly by regulating viral immediate-early 2 (IE2) protein levels. Furthermore, hnRNP K interacted with IE2 mRNA. Finally, GrM decreased IE2 protein expression in HCMV-infected cells. Our data suggest that targeting of hnRNP K by GrM contributes to the mechanism by which cytotoxic lymphocytes inhibit HCMV replication. This is the first evidence that cytotoxic lymphocytes target host cell proteins to control HCMV infections.