HIV-1 Nef triggers macrophage fusion in a p61Hck- and protease-dependent manner

Area of Science:

• Virology
• Immunology
• Cell Biology

Background:

• Macrophages are key targets for Human Immunodeficiency Virus type 1 (HIV-1) infection.
• HIV-1-infected macrophages can form multinucleated giant cells (MGCs), a characteristic feature in AIDS pathology, but the underlying mechanisms are not fully understood.

Purpose of the Study:

• To elucidate the role of the HIV-1 Nef protein in the formation of macrophage-derived MGCs.
• To identify the specific molecular players, including kinases and cellular components, involved in Nef-induced MGC formation.

Main Methods:

• Infection of human macrophages and RAW264.7 cells with wild-type and nef-deleted HIV-1.
• Expression of Nef protein and its mutants to assess MGC formation.
• Knockdown of hematopoietic cell kinase (Hck) and analysis of its isoforms (p61Hck).
• Investigation of lysosomal protein involvement in the fusion process.

Main Results:

• Deletion of the nef gene reduced MGC formation in HIV-1-infected macrophages.
• Expression of Nef alone was sufficient to induce MGC formation in macrophages.
• The polyproline motif of Nef, but not myristoylation, was crucial for MGC induction.
• Nef-induced MGC formation required the p61Hck isoform, specifically when localized to the lysosome membrane.
• Lysosomal proteins, including vacuolar adenosine triphosphatase and proteases, were implicated in Nef-mediated macrophage fusion.

Conclusions:

• The HIV-1 Nef protein plays a critical role in inducing macrophage fusion and MGC formation.
• Nef-induced MGC formation is dependent on the p61Hck kinase isoform and lysosomal enzymes.
• This study identifies novel molecular actors in HIV-1-induced macrophage fusion, offering insights into AIDS pathogenesis.