Intracellular sorting signals for sequential trafficking of human cytomegalovirus UL37 proteins to the endoplasmic reticulum and mitochondria.
Human cytomegalovirus UL37 antiapoptotic proteins, including the predominant UL37 exon 1 protein (pUL37x1), traffic sequentially from the endoplasmic reticulum (ER) through the mitochondrion-associated membrane compartment to the mitochondrial outer membrane (OMM), where they inactivate the proapoptotic activity of Bax. We found that widespread mitochondrial distribution occurs within 1 h of pUL37x1 synthesis. The pUL37x1 mitochondrial targeting signal (MTS) spans its first antiapoptotic domain (residues 5 to 34) and consists of a weak hydrophobicity leader (MTSalpha) and proximal downstream residues (MTSbeta). This MTS arrangement of a hydrophobic leader and downstream proximal basic residues is similar to that of the translocase of the OMM 20, Tom20. We examined whether the UL37 MTS functions analogously to Tom20 leader. Surprisingly, lowered hydropathy of the UL37x1 MTSalpha, predicted to block ER translocation, still allowed dual targeting of mutant to the ER and OMM. However, increased hydropathy of the MTS leader caused exclusion of the UL37x1 high-hydropathy mutant from mitochondrial import. Conversely, UL37 MTSalpha replacement with the Tom20 leader did not retarget pUL37x1 exclusively to the OMM; rather, the UL37x1-Tom20 chimera retained dual trafficking. Moreover, replacement of the UL37 MTSbeta basic residues did not reduce OMM import. Ablation of the MTSalpha posttranslational modification site or of the downstream MTS proline-rich domain (PRD) increased mitochondrial import. Our results suggest that pUL37x1 sequential ER to mitochondrial trafficking requires a weakly hydrophobic leader and is regulated by MTSbeta sequences. Thus, HCMV pUL37x1 uses a mitochondrial importation pathway that is genetically distinguishable from that of known OMM proteins.
Williamson
Chad D
CD
Center for Cancer and Immunology Research, Children's Research Institute, Children's National Medical Center, 111 Michigan Avenue, NW, Washington, DC 20010, USA.
Colberg-Poley
Anamaris M
AM
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D003587:Cytomegalovirus / Q000502:physiology*; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D017874:Immediate-Early Proteins / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D021382:Protein Sorting Signals; D021381:Protein Transport; D017385:Sequence Homology
D017874:Immediate-Early Proteins; D021382:Protein Sorting Signals; C420323:UL37 protein, Human herpesvirus 5
Proc Natl Acad Sci U S A. 1999 Oct 26;96(22):12536-41
10535957
J Mol Biol. 2005 Mar 18;347(1):81-93
15733919
Proc Natl Acad Sci U S A. 2003 Nov 25;100(24):14223-8
14623981
J Biol Chem. 2005 Jan 7;280(1):48-53
15501820
J Gen Virol. 2004 Jul;85(Pt 7):1989-1994
15218184
J Cell Biol. 2006 Sep 25;174(7):985-96
16982800
J Virol. 2006 Jul;80(14):6771-83
16809283
J Virol. 1992 Jan;66(1):95-105
1370097
Science. 2006 Mar 17;311(5767):1600-3
16543458
Proc Natl Acad Sci U S A. 2006 Dec 12;103(50):19117-22
17135350
J Cell Biol. 2006 Dec 18;175(6):901-11
17178908
Rev Med Virol. 2009 May;19(3):147-64
19367604
Curr Protoc Cell Biol. 2007 Dec;Chapter 3:Unit 3.27
18228515
Virology. 2003 Nov 25;316(2):221-33
14644605
BMC Bioinformatics. 2010 Jan 18;11 Suppl 1:S10
20122181
Virology. 1988 Jul;165(1):151-64
2838954
J Gen Virol. 2000 Jul;81(Pt 7):1779-89
10859384
J Virol. 2000 Nov;74(22):10816-8
11044129
Proc Natl Acad Sci U S A. 2003 Oct 14;100(21):12396-401
14519856
J Gen Virol. 2004 Dec;85(Pt 12):3555-3567
15557228
J Gen Virol. 2003 Dec;84(Pt 12):3353-3358
14645916
Mol Biol Cell. 2002 May;13(5):1615-25
12006657
J Virol. 1996 Oct;70(10):7198-208
8794367
Proteomics. 2004 Jun;4(6):1633-49
15174133
J Cell Biol. 2000 Oct 16;151(2):277-88
11038175
Nucleic Acids Res. 2002 Jan 1;30(1):235-8
11752303
J Biol Chem. 1989 Dec 15;264(35):21091-6
2687271
Virology. 2001 Jan 5;279(1):233-40
11145905
Annu Rev Biochem. 1997;66:863-917
9242927
Virology. 1999 Sep 1;261(2):155-64
10497101
Physiol Rev. 2006 Jan;86(1):369-408
16371601
J Biol Chem. 2003 Oct 24;278(43):42064-71
12917440
J Gen Virol. 2004 Feb;85(Pt 2):323-329
14769889
Proc Natl Acad Sci U S A. 2004 May 25;101(21):7988-93
15148411
EMBO J. 2006 Jun 7;25(11):2634-42
16688216
J Virol. 1990 May;64(5):2033-40
2157870
J Virol. 2005 Apr;79(8):5163-73
15795300
J Virol. 2003 Jan;77(1):631-41
12477866
PLoS Pathog. 2008 May 09;4(5):e1000063
18769594
Mol Biol Cell. 2005 Apr;16(4):1788-99
15673615
Cell. 2009 Mar 6;136(5):891-902
19269366
J Biol Chem. 2004 May 21;279(21):22605-14
15004026
J Virol. 2008 Mar;82(6):2715-26
18199645
Oncogene. 2007 Nov 1;26(50):7067-80
17496930
J Cell Biol. 2006 Sep 25;174(7):915-21
16982799
J Virol. 2008 Jul;82(13):6232-43
18417572
J Gen Virol. 2004 Dec;85(Pt 12):3541-3553
15557227
J Biol Chem. 2000 Nov 3;275(44):34534-40
10938271