The Salmonella virulence protein SifA is a G protein antagonist.
Salmonella's success at proliferating intracellularly and causing disease depends on the translocation of a major virulence protein, SifA, into the host cell. SifA recruits membranes enriched in lysosome associated membrane protein 1 (LAMP1) and is needed for growth of Salmonella induced filaments (Sifs) and the Salmonella containing vacuole (SCV). It directly binds a host protein called SKIP (SifA and kinesin interacting protein) which is critical for membrane stability and motor dynamics at the SCV. SifA also contains a WxxxE motif, predictive of G protein mimicry in bacterial effectors, but whether and how it mimics the action of a host G protein is not known. We show that SKIP's pleckstrin homology domain, which directly binds SifA, also binds to the late endosomal GTPase Rab9. Knockdown studies suggest that both SKIP and Rab9 function to maintain peripheral LAMP1 distribution in cells. The Rab9:SKIP interaction is GTP-dependent and is inhibited by SifA binding to the SKIP pleckstrin homology domain, suggesting that SifA may be a Rab9 antagonist. SifA:SKIP binding is significantly tighter than Rab9:SKIP binding and may thus allow SifA to bring SKIP to the SCV via SKIP's Rab9-binding site. Rab9 can measurably reverse SifA-dependent LAMP1 recruitment and the perinuclear location of the SCV in cells. Importantly, binding to SKIP requires SifA residues W197 and E201 of the conserved WxxxE signature sequence, leading to the speculation that bacterial G protein mimicry may result in G protein antagonism.
Jackson
Laurie K
LK
Department of Pathology, Northwestern University, Feinberg School of Medicine, Chicago, IL 60611, USA.
Nawabi
Parwez
P
Hentea
Cristiana
C
Roark
Everett A
EA
Haldar
Kasturi
K
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D006023:Glycoproteins / Q000235:genetics / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D052118:Lysosomal-Associated Membrane Protein 1 / Q000378:metabolism; D011485:Protein Binding; D012486:Salmonella typhimurium / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity*; D014774:Virulence; D037521:Virulence Factors; D020691:rab GTP-Binding Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism
D001426:Bacterial Proteins; D006023:Glycoproteins; D052118:Lysosomal-Associated Membrane Protein 1; C421862:SifA protein, Salmonella; D037521:Virulence Factors; D006160:Guanosine Triphosphate; D020691:rab GTP-Binding Proteins
Mol Biol Cell. 2004 Jul;15(7):3146-54
15121880
J Biol Chem. 2003 Apr 18;278(16):14196-202
12574170
Biochem Soc Trans. 2004 Nov;32(Pt 5):707-11
15493994
Mol Microbiol. 2008 Apr;68(1):173-85
18333886
Proc Natl Acad Sci U S A. 1996 Mar 19;93(6):2593-7
8637919
J Cell Biol. 2006 Nov 6;175(3):453-63
17074883
Proc Natl Acad Sci U S A. 2006 Aug 8;103(32):11821-7
16882731
Proc Natl Acad Sci U S A. 1993 Nov 15;90(22):10544-8
8248143
J Biochem. 1987 Sep;102(3):503-11
3323191
Infect Immun. 2005 Sep;73(9):5438-49
16113260
J Biol Chem. 2003 Mar 7;278(10):8494-500
12493736
EMBO J. 2000 Jul 3;19(13):3235-49
10880437
Nat Cell Biol. 2006 Sep;8(9):971-7
16906144
J Cell Biol. 2007 Jan 29;176(3):263-8
17261845
J Cell Biol. 1995 Apr;129(1):81-97
7698996
Science. 2005 May 20;308(5725):1174-8
15905402
Microbiol Mol Biol Rev. 2007 Dec;71(4):636-52
18063721
J Biol Chem. 2004 Aug 6;279(32):33430-7
15173169
J Biol Chem. 2003 Jun 6;278(23):21099-104
12657629
Blood. 2008 Feb 15;111(4):2418-26
18057226
EMBO J. 2005 Apr 20;24(8):1491-501
15933719
Mol Microbiol. 1996 Apr;20(1):151-64
8861213
Nat Rev Microbiol. 2005 May;3(5):397-410
15821726
Mol Microbiol. 2002 May;44(3):645-61
11994148
Nat Biotechnol. 2004 Dec;22(12):1567-72
15558047
Mol Biol Cell. 2004 Dec;15(12):5420-30
15456905
EMBO J. 1999 Aug 16;18(16):4394-403
10449405
Biochem Biophys Res Commun. 2006 May 5;343(2):666-74
16554019
Cell Microbiol. 2001 Feb;3(2):75-84
11207622
Cell. 2006 Jan 13;124(1):133-45
16413487
EMBO J. 1993 Feb;12(2):677-82
8440258
EMBO J. 2003 Oct 1;22(19):5003-14
14517239
Nat Struct Mol Biol. 2006 Dec;13(12):1135-40
17115053