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The human cytomegalovirus protein UL37 exon 1 associates with internal lipid rafts

Chad D Williamson1, Aiping Zhang, Anamaris M Colberg-Poley

  • 1Children's Research Institute, Children's National Medical Center, Washington, DC 20010, USA.

Journal of Virology
|December 24, 2010
PubMed

Insights

Human cytomegalovirus protein pUL37x1 (vMIA) associates with internal lipid rafts in the ER/MAM, independent of mitochondrial targeting. This interaction, dependent on cholesterol, is crucial for HCMV infection and distinct from its apoptosis inhibition role.

Area of Science:

  • * Virology
  • * Cell Biology
  • * Molecular Biology

Background:

  • * Human cytomegalovirus (HCMV) protein UL37 exon 1 (pUL37x1), or viral mitochondrion-localized inhibitor of apoptosis (vMIA), inhibits apoptosis by trafficking to the outer mitochondrial membrane.
  • * Mitochondrion-associated membranes (MAMs) are critical for lipid transfer and calcium signaling, enriched in cholesterol and ceramide, forming detergent-resistant membranes (DRMs).
  • * Sigma 1 receptor (Sig-1R), a MAM chaperone, anchors to MAMs via lipid raft association.

Purpose of the Study:

  • * To investigate the association of pUL37x1/vMIA with internal lipid rafts (LRs) within the ER/MAM.
  • * To determine if this association is linked to its trafficking and function during HCMV infection.
  • * To elucidate the molecular basis and functional significance of pUL37x1/vMIA's interaction with MAM LRs.

Main Methods:

  • * Methyl-β-cyclodextrin (MβCD) extraction to assess LR association in lysed and intact cells.
  • * Isolation of detergent-resistant membranes (DRMs) from purified intracellular organelles.
  • * Analysis of pUL37x1/vMIA localization and association during various stages of HCMV infection.

Main Results:

  • * pUL37x1/vMIA was found to associate with internal LRs in the ER/MAM, confirmed by MβCD extraction and DRM isolation.
  • * This LR association was observed throughout all phases of HCMV infection.
  • * The association with LRs was independent of mitochondrial targeting signals but dependent on cholesterol binding.
  • * pUL37x1/vMIA was not detected in DRMs isolated from mitochondria.

Conclusions:

  • * pUL37x1/vMIA interacts with cholesterol-dependent LRs in the ER/MAM during HCMV infection.
  • * This LR association is functionally distinct from its role in apoptosis inhibition and mitochondrial trafficking.
  • * The findings suggest a conserved mechanism for UL37 proteins involving cholesterol and LR interactions, important for viral replication.

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