Targeting of murine leukemia virus gag to the plasma membrane is mediated by PI(4,5)P2/PS and a polybasic region in...

Area of Science:

• Virology
• Molecular Biology
• Cell Biology

Background:

• Membrane targeting of human immunodeficiency virus Gag proteins is crucial for viral replication and depends on plasma membrane phosphatidylinositol-(4,5)-bisphosphate [PI(4,5)P(2)].
• Understanding the conserved mechanisms of retroviral Gag protein membrane association is vital for developing antiviral strategies.

Purpose of the Study:

• To investigate whether evolutionarily distant retroviral Gag proteins utilize similar mechanisms for membrane targeting.
• To elucidate the role of the matrix (MA) domain of murine leukemia virus (MuLV) Gag in phosphatidylinositol phosphate binding and plasma membrane localization.

Main Methods:

• Generation and analysis of MuLV Gag matrix (MA) domain mutants.
• In vitro binding assays using membrane models to assess MA domain affinity for various phosphatidylinositol phosphates.
• Cell culture experiments to evaluate the impact of MA mutations and PI(4,5)P(2) levels on Gag localization, membrane binding, and virion production.

Main Results:

• The MuLV MA domain exhibited significant binding affinity for all phosphatidylinositol phosphates, with a strong specificity for PI(4,5)P(2) when enhanced by phosphatidylserine.
• Mutations within the MA polybasic region substantially reduced PI(4,5)P(2) binding affinity.
• In cellular contexts, PI(4,5)P(2) depletion impaired virus production, and MA polybasic region mutations altered Gag localization, membrane association, and virion release.

Conclusions:

• The N-terminal polybasic cluster of the MuLV MA domain is essential for Gag protein targeting to the plasma membrane.
• Binding of the MA domain to PI(4,5)P(2) represents a conserved feature among retroviruses, even with structural differences in the MA domain compared to HIV.
• This conserved interaction highlights a potential target for broad-spectrum retroviral inhibitors.