Functional and Structural Insights into a Vif/PPP2R5 Complex Elucidated Using Patient HIV-1 Isolates and...

Area of Science:

• Virology
• Molecular Biology
• Cell Biology

Background:

• Human immunodeficiency virus type 1 (HIV-1) Vif protein antagonizes APOBEC3 enzymes, an innate immune defense.
• HIV-1 Vif is also known to induce G2/M cell cycle arrest by degrading PPP2R5 phosphoregulators.

Purpose of the Study:

• To delineate the structural basis of the Vif/PPP2R5 complex using computational docking.
• To investigate the functional consequences of Vif-mediated PPP2R5 degradation on viral pathogenesis.
• To determine if Vif can concurrently degrade distinct cellular substrates like PPP2R5 and APOBEC3.

Main Methods:

• Computational protein-protein docking to model the Vif/CBF-β/PPP2R5 complex.
• Targeted mutagenesis to assess Vif-PPP2R5 interactions and degradation.
• Peptide inhibition assays to distinguish Vif-mediated degradation pathways.
• Live-cell imaging to compare degradation kinetics of PPP2R5A and APOBEC3G.
• Analysis of patient-derived Vif isolates for PPP2R5A degradation activity.

Main Results:

• A Vif/CBF-β/PPP2R5 complex model predicted Vif binding to the same PPP2R5 surface as physiological targets.
• Mutagenesis confirmed the importance of the putative interface for Vif-induced PPP2R5 degradation.
• Vif concurrently degraded PPP2R5A and APOBEC3G with similar kinetics (half-life ~6 hours).
• PPP2R5A degradation activity was prevalent in patient-derived HIV-1 Vif isolates.

Conclusions:

• HIV-1 Vif degrades PPP2R5 phosphoregulators, contributing to G2/M cell cycle arrest and viral pathogenesis.
• Vif possesses the capacity to simultaneously degrade distinct cellular substrates, including antiviral factors and cell cycle regulators.
• The degradation of PPP2R5 proteins is a conserved and significant function of HIV-1 Vif across diverse patient isolates.