Sphingomyelin synthase 2, but not sphingomyelin synthase 1, is involved in HIV-1 envelope-mediated membrane fusion

J Biol Chem. 2014 Oct 31;289(44):30842-56. doi: 10.1074/jbc.M114.574285. Epub 2014 Sep 17.

Abstract

Membrane fusion between the viral envelope and plasma membranes of target cells has previously been correlated with HIV-1 infection. Lipids in the plasma membrane, including sphingomyelin, may be crucially involved in HIV-1 infection; however, the role of lipid-metabolic enzymes in membrane fusion remains unclear. In this study, we examined the roles of sphingomyelin synthase (SMS) in HIV-1 Env-mediated membrane fusion using a cell-cell fusion assay with HIV-1 mimetics and their target cells. We employed reconstituted cells as target cells that stably express Sms1 or Sms2 in Sms-deficient cells. Fusion susceptibility was ∼5-fold higher in Sms2-expressing cells (not in Sms1-expressing cells) than in Sms-deficient cells. The enhancement of fusion susceptibility observed in Sms2-expressing cells was reversed and reduced by Sms2 knockdown. We also found that catalytically nonactive Sms2 promoted membrane fusion susceptibility. Moreover, SMS2 co-localized and was constitutively associated with the HIV receptor·co-receptor complex in the plasma membrane. In addition, HIV-1 Env treatment resulted in a transient increase in nonreceptor tyrosine kinase (Pyk2) phosphorylation in Sms2-expressing and catalytically nonactive Sms2-expressing cells. We observed that F-actin polymerization in the region of membrane fusion was more prominent in Sms2-expressing cells than Sms-deficient cells. Taken together, our research provides insight into a novel function of SMS2 which is the regulation of HIV-1 Env-mediated membrane fusion via actin rearrangement.

Keywords: Cell-Cell Fusion Assay; Human Immunodeficiency Virus (HIV); Membrane Fusion; Membrane Lipid; Phospholipid; Sphingolipid; Sphingomyelin Synthase.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / metabolism
  • Animals
  • Cell Membrane / enzymology
  • Cell Membrane / virology
  • Enzyme Activation
  • Focal Adhesion Kinase 2 / metabolism
  • Gene Expression
  • HIV-1 / physiology*
  • Humans
  • Jurkat Cells
  • Membrane Proteins / physiology*
  • Mice, Knockout
  • Nerve Tissue Proteins / physiology*
  • Protein Multimerization
  • Protein Transport
  • Receptors, HIV / metabolism
  • Transferases (Other Substituted Phosphate Groups) / physiology*
  • Virus Attachment
  • Virus Internalization*

Substances

  • Actins
  • Membrane Proteins
  • Nerve Tissue Proteins
  • Receptors, HIV
  • Focal Adhesion Kinase 2
  • SGMS1 protein, human
  • Transferases (Other Substituted Phosphate Groups)