Breana Santos
Research Mentor(s): Ricardo de Souza Cardoso
Mentor Department: Microbiology and Immunology
Authors: Breana Santos, Akira Ono, Ricardo de Souza Cardoso
Session: Session 7 (4:00pm – 4: 50pm)
Presentation Type: Oral
Abstract
HIV-1 assembly occurs at the plasma membrane (PM) and is orchestrated by the viral polyprotein Gag. The Highly Basic Region (HBR) of the matrix (MA) domain interacts with the negatively charged lipid phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2), anchoring Gag to the PM. At the PM, Gag multimerizes through two mechanisms: capsid (CA)-mediated protein-protein interactions and nucleocapsid (NC)-mediated binding to the viral genome. Concurrently, the HIV Env protein is recruited for incorporation into virions. In addition to viral components, various host transmembrane proteins (HCTMPs) are incorporated into HIV-1 particles, influencing infectivity. While CD43 and PSGL-1 hinder viral attachment, CD44 enhances trans-infection by lymph node stromal cells. Our recent study demonstrated that PI(4,5)P2 accumulates around Gag at assembly sites and bridges the association between the positively charged cytoplasmic tails of HCTMPs and the MA HBR, promoting their incorporation into HIV-1. This highlights the critical role of PI(4,5)P2 in recruiting HCTMPs into viral particles. Despite its importance, the mechanisms driving PI(4,5)P2 enrichment at assembly sites remain unclear. We hypothesize that Gag multimerization facilitates this process by increasing local PI(4,5)P2 concentration through electrostatic recruitment, which in turn enhances HCTMP recruitment and incorporation into HIV-1. To test this, we investigated whether CA- and NC-mediated Gag multimerization promotes PI(4,5)P2 and HCTMP accumulation at assembly sites. Using expansion microscopy—an innovative super-resolution technique that physically enlarges samples for nanoscale imaging—combined with a novel quantification approach, we measured the shortest distances between wild-type (WT) or multimerization-deficient Gag to PI(4,5)P2 and the HCTMPs. Our results reveal that multimerization-deficient viruses exhibit greater distances between Gag and HCTMPs compared to WT viruses. Collectively, these data suggest that Gag multimerization plays a key role in sorting CD43, PSGL-1, and CD44 into HIV-1 assembly sites.
