Contribution of PDZD8 to Stabilization of the Human Immunodeficiency Virus (HIV-1) Capsid

Following human immunodeficiency virus (HIV-1) entry into the host cell, the viral capsid gradually disassembles in a process called uncoating. A proper rate of uncoating is important for reverse transcription of the HIV-1 genome. Host restriction factors such as TRIM5α and TRIMCyp bind retroviral capsids and cause premature disassembly, leading to blocks in reverse transcription. Other host factors, such as cyclophilin A, stabilize the HIV-1 capsid and are required for efficient infection in some cell types. To identify additional cellular factors that alter retroviral core uncoating, we developed a novel in vitro assay of HIV-1 capsid stability. Using this assay, we have shown that a factor in the cytoplasm of cells from multiple vertebrate species slows the spontaneous disassembly of HIV-1 capsid-nucleocapsid (CA-NC) complexes in vitro. We identified the PDZ-Domain-containing protein 8 (PDZD8) as a critical component of the capsid-stabilizing activity in the cytoplasmic extracts. PDZD8 has been previously reported to bind the HIV-1 Gag polyprotein and to make a positive contribution to the efficiency of HIV-1 infection. PDZD8 knockdown accelerated the disassembly of HIV-1 capsids in infected cells, resulting in decreased reverse transcription. The PDZD8 coiledcoil domain is sufficient for HIV-1 capsid binding, but other parts of the protein, including the PDZ domain, are apparently required for stabilizing the capsid and supporting HIV-1 infection. In summary, PDZD8 interacts with and stabilizes the HIV-1 capsid and thus represents a potentially targetable host cofactor for HIV-1 infection.