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Journal of Virology, August 2009, p. 7467-7474, Vol. 83, No. 15
0022-538X/09/$08.00+0     doi:10.1128/JVI.00163-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Formation of Syncytia Is Repressed by Tetraspanins in Human Immunodeficiency Virus Type 1-Producing Cells{triangledown}

Jia Weng,1,2 Dimitry N. Krementsov,1,3 Sandhya Khurana,1,2 Nathan H. Roy,1,3 and Markus Thali1,2,3*

Department of Microbiology and Molecular Genetics,1 Graduate Programs in Microbiology and Molecular Genetics,2 Cellular and Molecular Biology, University of Vermont, Burlington, Vermont 054053

Received 23 January 2009/ Accepted 11 May 2009

In vitro propagation studies have established that human immunodeficiency virus type 1 (HIV-1) is most efficiently transmitted at the virological synapse that forms between producer and target cells. Despite the presence of the viral envelope glycoprotein (Env) and CD4 and chemokine receptors at the respective surfaces, producer and target cells usually do not fuse with each other but disengage after the viral particles have been delivered, consistent with the idea that syncytia, at least in vitro, are not required for HIV-1 spread. Here, we tested whether tetraspanins, which are well known regulators of cellular membrane fusion processes that are enriched at HIV-1 exit sites, regulate syncytium formation. We found that overexpression of tetraspanins in producer cells leads to reduced syncytium formation, while downregulation has the opposite effect. Further, we document that repression of Env-induced cell-cell fusion by tetraspanins depends on the presence of viral Gag, and we demonstrate that fusion repression requires the recruitment of Env by Gag to tetraspanin-enriched microdomains (TEMs). However, sensitivity to fusion repression by tetraspanins varied for different viral strains, despite comparable recruitment of their Envs to TEMs. Overall, these data establish tetraspanins as negative regulators of HIV-1-induced cell-cell fusion, and they start delineating the requirements for this regulation.

* Corresponding author. Mailing address: 318 Stafford Hall, University of Vermont, Burlington, VT 05405. Phone: (802) 656-1056. Fax: (802) 656-4789. E-mail: markus.thali{at}uvm.edu

{triangledown} Published ahead of print on 20 May 2009.

Journal of Virology, August 2009, p. 7467-7474, Vol. 83, No. 15
0022-538X/09/$08.00+0     doi:10.1128/JVI.00163-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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