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Role of human immunodeficiency virus type 1 matrix phosphorylation in an early postentry step of virus replication

Rajnish Kaushik1, Lee Ratner

  • 1Department of Medicine, Pathology, and Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.

Journal of Virology
|February 14, 2004
PubMed

Insights

Mutations in human immunodeficiency virus type 1 matrix protein (MA) serine residues impair viral infectivity by affecting an early postentry step. Phosphorylation of these serine sites is crucial for efficient viral replication.

Area of Science:

  • Virology
  • Molecular Biology
  • Cell Biology

Background:

  • The matrix domain (MA) of human immunodeficiency virus type 1 (HIV-1) Gag is essential for multiple stages of the viral life cycle, including plasma membrane targeting, virion incorporation, and nuclear import of the preintegration complex.
  • Myristylation and phosphorylation are critical regulatory modifications for MA function, with previous research highlighting the importance of serine (Ser) phosphorylation for viral replication.

Purpose of the Study:

  • To elucidate the molecular mechanisms underlying HIV-1 virus particle assembly and infectivity by investigating the specific role of MA serine phosphorylation.
  • To determine the impact of mutations in key serine residues of MA on viral infectivity and replication.

Main Methods:

  • Site-directed mutagenesis was used to create combined mutations of serine residues at positions 9, 67, 72, and 77 in the HIV-1 MA protein.
  • Viral infectivity assays were performed in both dividing and non-dividing cells to assess the functional consequences of these mutations.
  • Pseudotyping experiments using vesicular stomatitis virus G protein were conducted to investigate the stage of the viral life cycle affected by the MA mutations.
  • Phosphorylation levels of MA in mutant and wild-type viruses were analyzed.

Main Results:

  • Combined mutation of Ser-9, -67, -72, and -77 in MA significantly impaired viral infectivity in both dividing and non-dividing cells.
  • Virus particle assembly for these serine mutant viruses was comparable to wild-type HIV-1, indicating the defect occurs post-assembly.
  • The infectivity defect in serine mutant viruses could be rescued by pseudotyping with vesicular stomatitis virus G protein, pointing to a critical role in an early postentry step.
  • Phosphorylation levels of MA were severely reduced in the defective mutant viruses compared to wild-type, correlating mutation with reduced phosphorylation.

Conclusions:

  • Phosphorylation of MA at Ser-9, -67, -72, and -77 is essential for an early postentry step in the HIV-1 life cycle.
  • These specific serine residues are critical for viral infectivity, likely through regulating post-assembly events after viral entry.
  • Understanding these phosphorylation-dependent mechanisms provides insights into HIV-1 replication and potential therapeutic targets.

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