HIV-1 Vpu utilizes both cullin-RING ligase CRL dependent and independent mechanisms to downmodulate host proteinsReport as inadecuate




HIV-1 Vpu utilizes both cullin-RING ligase CRL dependent and independent mechanisms to downmodulate host proteins - Download this document for free, or read online. Document in PDF available to download.

Retrovirology

, 12:65

First Online: 28 July 2015Received: 02 February 2015Accepted: 22 July 2015

Abstract

BackgroundHijacking of the cullin-RING E3 ubiquitin ligase CRL machinery is a common mechanism employed by diverse groups of viruses for the efficient counteraction and degradation of host proteins. In particular, HIV-1 Vpu usurps the SCF E3 ubiquitin ligase complex to mark CD4 for degradation by the 26S proteasome. Vpu also interacts with and downmodulates a number of other host proteins, including the restriction factor BST-2. However, whether Vpu primarily relies on a cullin-dependent or -independent mechanism to antagonize its cellular targets has not been fully elucidated.

ResultsWe utilized a sulphamate AMP analog, MLN4924, to effectively block the activation of CRLs within infected primary CD4 T cells. MLN4924 treatment, in a dose dependent manner, efficiently relieved surface downmodulation and degradation of CD4 by NL4-3 Vpu. MLN4924 inhibition was highly specific, as this inhibitor had no effect on Nef’s ability to downregulate CD4, which is accomplished by a CRL-independent mechanism. In contrast, NL4-3 Vpu’s capacity to downregulate BST-2, NTB-A and CCR7 was not inhibited by the drug. Vpu’s from both a transmitted founder T-F and chronic carrier CC virus preserved the ability to downregulate BST-2 in the presence of MLN4924. Finally, depletion of cellular pools of cullin 1 attenuated Vpu’s ability to decrease CD4 but not BST-2 surface levels.

ConclusionsWe conclude that Vpu employs both CRL-dependent and CRL-independent modes of action against host proteins. Notably, we also establish that Vpu-mediated reduction of BST-2 from the cell surface is independent of β-TrCP and the CRL- machinery and this function is conserved by Vpu’s from primary isolates. Therefore, potential therapies aimed at antagonizing the activities of Vpu may need to address these distinct mechanisms of action in order to achieve a maximal effect.

KeywordsCRL Vpu MLN4924 Nef CD4 BST-2 NTB-A CCR7 AbbreviationsCRLcullin-RING ligase

RINGreally interesting new gene

AP-1Adaptor-Protein 1

Vpuviral protein u

Peter W Ramirez and Ana Beatriz DePaula-Silva contributed equally to this work

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Author: Peter W Ramirez - Ana Beatriz DePaula-Silva - Matt Szaniawski - Edward Barker - Alberto Bosque - Vicente Planelles

Source: https://link.springer.com/article/10.1186/s12977-015-0192-2



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