Human cytomegalovirus (HCMV) is a medically significant herpesvirus. Viral growth relies upon the proper production, localization, and function of its key proteins. The predominant products of the UL37 immediate early (IE) locus during HCMV infection are the essential UL37 exon 1 protein (pUL37x1) and a UL37 glycoprotein (gpUL37). Physical dissociation and differential trafficking are unique features of UL37 IE products, which appear to traffic to the ER and to mitochondria. This trafficking is sequential: gpUL37 is N-glycosylated and protease cleaved in the ER, so that its C-terminus is ER-retained while its N-terminus is imported into mitochondria where it inhibits apoptosis. Exceptionally few cellular mitochondrial proteins originate in the ER. The overall goal of this proposal is to examine the mechanistic basis for UL37 protein trafficking, processing, and functional role(s) during HCMV infection. We hypothesize that HCMV UL37 IE proteins traffic from the ER to mitochondria by targeting the mitochondria associated membrane (MAM) fraction and that the unique domains of UL37 isoforms result in differential trafficking and diverse functions.
In Aim 1, we will test if UL37 protein trafficking through the secretory apparatus and mitochondria are interrelated. We will perform pulse-chase studies and subcellular localization of UL37 proteins in HCMV-infected cells as well as live cell imaging to determine if UL37 proteins traffic from ER to mitochondria.
In Aim 2, we will examine post-translational processing of pUL37x1 and gpUL37, generate and assay UL37 mutants to determine which residues alter processing, trafficking, and function.
In Aim 3, the function of HCMV UL37 proteins will be examined in the context of viral infection. We will complement, with the corresponding UL37 isoforms, an HCMV UL37 exon 3 mutant, which is growth delayed in G0-human fibroblasts. The induction of cellular gene expression in parental or in UL37 mutant HCMV-infected differentiated cells will be analyzed by microarray analysis. A thorough understanding of the regulation of how the essential UL37 proteins traffic to their ultimate locations and their function in infected cells is of fundamental importance in understanding the HCMV life cycle and its pathogenesis. Deciphering UL37 protein trafficking may provide valuable insight into cellular ER to mitochondrial trafficking pathways and, ultimately, be used against HCMV for therapeutic benefit.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI057906-05
Application #
7570619
Study Section
Virology - B Study Section (VIRB)
Program Officer
Beisel, Christopher E
Project Start
2005-06-01
Project End
2012-02-28
Budget Start
2009-03-01
Budget End
2012-02-28
Support Year
5
Fiscal Year
2009
Total Cost
$308,815
Indirect Cost
Name
Children's Research Institute
Department
Type
DUNS #
143983562
City
Washington
State
DC
Country
United States
Zip Code
20010
Williamson, Chad D; Wong, Daniel S; Bozidis, Petros et al. (2015) Isolation of Endoplasmic Reticulum, Mitochondria, and Mitochondria-Associated Membrane and Detergent Resistant Membrane Fractions from Transfected Cells and from Human Cytomegalovirus-Infected Primary Fibroblasts. Curr Protoc Cell Biol 68:3.27.1-33
Zhang, Aiping; Hildreth, Richard L; Colberg-Poley, Anamaris M (2013) Human cytomegalovirus inhibits apoptosis by proteasome-mediated degradation of Bax at endoplasmic reticulum-mitochondrion contacts. J Virol 87:5657-68
Hildreth, Richard L; Bullough, Matthew D; Zhang, Aiping et al. (2012) Viral mitochondria-localized inhibitor of apoptosis (UL37 exon 1 protein) does not protect human neural precursor cells from human cytomegalovirus-induced cell death. J Gen Virol 93:2436-46
Williamson, Chad D; DeBiasi, Roberta L; Colberg-Poley, Anamaris M (2012) Viral product trafficking to mitochondria, mechanisms and roles in pathogenesis. Infect Disord Drug Targets 12:18-37
Williamson, Chad D; Zhang, Aiping; Colberg-Poley, Anamaris M (2011) The human cytomegalovirus protein UL37 exon 1 associates with internal lipid rafts. J Virol 85:2100-11
Gaddy, Charla E; Wong, Daniel S; Markowitz-Shulman, Ariel et al. (2010) Regulation of the subcellular distribution of key cellular RNA-processing factors during permissive human cytomegalovirus infection. J Gen Virol 91:1547-59
Williamson, Chad D; Colberg-Poley, Anamaris M (2010) Intracellular sorting signals for sequential trafficking of human cytomegalovirus UL37 proteins to the endoplasmic reticulum and mitochondria. J Virol 84:6400-9
Bozidis, Petros; Williamson, Chad D; Wong, Daniel S et al. (2010) Trafficking of UL37 proteins into mitochondrion-associated membranes during permissive human cytomegalovirus infection. J Virol 84:7898-903
Williamson, Chad D; Colberg-Poley, Anamaris M (2009) Access of viral proteins to mitochondria via mitochondria-associated membranes. Rev Med Virol 19:147-64
Bozidis, Petros; Williamson, Chad D; Colberg-Poley, Anamaris M (2008) Mitochondrial and secretory human cytomegalovirus UL37 proteins traffic into mitochondrion-associated membranes of human cells. J Virol 82:2715-26

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