Present address: Division of Biological Sciences, The University of Montana, Missoula, MT 59812, USA.
Ubiquitination of the bacterial inositol phosphatase, SopB, regulates its biological activity at the plasma membrane
Article first published online: 13 JUL 2009
© Published 2009. This article is a US Government work and is in the public domain in the USA
Volume 11, Issue 11, pages 1652–1670, November 2009
How to Cite
Knodler, L. A., Winfree, S., Drecktrah, D., Ireland, R. and Steele-Mortimer, O. (2009), Ubiquitination of the bacterial inositol phosphatase, SopB, regulates its biological activity at the plasma membrane. Cellular Microbiology, 11: 1652–1670. doi: 10.1111/j.1462-5822.2009.01356.x
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- Issue published online: 8 OCT 2009
- Article first published online: 13 JUL 2009
- Received 27 March, 2009; revised 27 June, 2009; accepted 3 July, 2009.
The Salmonella type III effector, SopB, is an inositol polyphosphate phosphatase that modulates host cell phospholipids at the plasma membrane and the nascent Salmonella-containing vacuole (SCV). Translocated SopB persists for many hours after infection and is ubiquitinated but the significance of this covalent modification has not been investigated. Here we identify by mass spectrometry six lysine residues of SopB that are mono-ubiquitinated. Substitution of these six lysine residues with arginine, SopB-K6R, almost completely eliminated SopB ubiquitination. We found that ubiquitination does not affect SopB stability or membrane association, or SopB-dependent events in SCV biogenesis. However, two spatially and temporally distinct events are dependent on ubiquitination, downregulation of SopB activity at the plasma membrane and prolonged retention of SopB on the SCV. Activation of the mammalian pro-survival kinase Akt/PKB, a downstream target of SopB, was intensified and prolonged after infection with the SopB-K6R mutant. At later times, fewer SCV were decorated with SopB-K6R compared with SopB. Instead SopB-K6R was present as discrete vesicles spread diffusely throughout the cell. Altogether, our data show that ubiquitination of SopB is not related to its intracellular stability but rather regulates its enzymatic activity at the plasma membrane and intracellular localization.