Contribution of PDZD8 to stabilization of the human immunodeficiency virus type 1 capsid.

Following human immunodeficiency virus type 1 (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. Here, we show that a heat-labile factor greater than 100 kDa 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 (M. S. Henning, S. G. Morham, S. P. Goff, and M. H. Naghavi, J. Virol. 84:: 8990-8995, 2010, doi:10.1128/JVI.00843-10). PDZD8 knockdown accelerated the disassembly of HIV-1 capsids in infected cells, resulting in decreased reverse transcription. The PDZD8 coiled-coil 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. After human immunodeficiency virus type 1 (HIV-1) gains access to the interior of the target cell, host cell factors can influence virus infection in either a positive or negative way. HIV-1 depends upon certain host cell factors to assist processes that are required for virus replication. One example of such a host factor is PDZD8. This work shows that PDZD8 helps to stabilize the HIV-1 capsid, a huge complex of the viral RNA, enzymes, and protein. When PDZD8 is prevented from interacting with the HIV-1 capsid, the capsid becomes unstable and HIV-1 infection is inhibited. These results show that PDZD8 regulates the uncoating of the HIV-1 capsid. Interfering with the interaction of PDZD8 and capsid could prove to be a useful strategy for intervening in HIV-1 infection and transmission.