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Infection and Immunity, June 2008, p. 2722-2735, Vol. 76, No. 6
0019-9567/08/$08.00+0     doi:10.1128/IAI.00152-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Role for Myosin II in Regulating Positioning of Salmonella-Containing Vacuoles and Intracellular Replication

Julie A. Wasylnka,¹ Malina A. Bakowski,^1,2,¶ Jason Szeto,^1,¶ Maikke B. Ohlson,⁵ William S. Trimble,^1,4 Samuel I. Miller,^5,6,7 and John H. Brumell^1,2,3*

Cell Biology Program, Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada,¹ Department of Molecular Genetics,² Institute of Medical Science,³ Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada,⁴ Departments of Microbiology,⁵ Genome Sciences,⁶ Medicine, University of Washington, Seattle, Washington 98195-7710⁷

Received 5 February 2008/ Returned for modification 13 March 2008/ Accepted 3 April 2008

Salmonella enterica serovar Typhimurium grows within host cells in a permissive compartment termed the Salmonella-containing vacuole (SCV). These bacteria use two distinct type III secretion systems (T3SS) to deliver virulence proteins (effectors) into cells. Effectors secreted by the Salmonella pathogenicity island 1 (SPI-1)-encoded T3SS mediate invasion and early SCV maturation steps, while those secreted by the SPI-2 T3SS affect the SCV at later stages postinfection. Some SPI-2 effectors modulate microtubule motor activity on the SCV. Here, we show that the actin-based motor myosin II also affects SCV dynamics during infection. Following invasion, myosin II is required for SCV positioning near the nucleus of host cells. Later, myosin II counteracts the activities of the SPI-2 effectors PipB2 and SseJ to maintain SCV positioning and stability, respectively. Myosin II activity was required for maximal bacterial growth in macrophages. Rho kinase activity was required for SCV positioning. The effector SopB, a known activator of Rho GTPases, was found to be required for SCV positioning, and transfection of cells with SopB was sufficient to induce myosin II phosphorylation. These studies reveal a novel role for myosin II in controlling SCV dynamics during infection and suggest that SopB activates myosin II.

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* Corresponding author. Mailing address: Cell Biology Program, Hospital for Sick Children, 555 University Avenue, Toronto, ON M5G 1X8, Canada. Phone: (416) 813-7654, ext. 3555. Fax: (416) 813-5028. E-mail: john.brumell{at}sickkids.ca

Published ahead of print on 14 April 2008.

Editor: A. J. Bäumler

^¶ These authors contributed equally to the work in the paper.

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Infection and Immunity, June 2008, p. 2722-2735, Vol. 76, No. 6
0019-9567/08/$08.00+0     doi:10.1128/IAI.00152-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

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