Human T-cell leukemia virus 1 envelope glycoprotein gp21 (gp21)

Human T-cell leukemia virus 1 envelope glycoprotein gp21 (gp21) is the transmembrane (TM) subunit of the HTLV-1 envelope complex, playing a vital role in viral entry and pathogenesis (UniProt A0A023HB55). It is synthesized as part of the gp62 precursor, which is cleaved by cellular proteases into the surface subunit (gp46) and the transmembrane subunit (gp21). As a Class I viral fusion protein, gp21 mediates the fusion of the viral envelope with the host cell membrane or the fusion of infected and uninfected cells through the formation of a virological synapse (PubMed: 15890939). This process involves a dramatic conformational change where gp21 refolds into a stable six-helix bundle, bringing the viral and cellular membranes into close proximity for merger (PubMed: 10823903). Beyond its structural role, the fusion peptide of gp21 has been implicated in modulating host immune responses, potentially contributing to the immunosuppression observed in HTLV-1-infected individuals (PubMed: 29727456). HTLV-1 infection is the causative agent of severe conditions such as adult T-cell leukemia/lymphoma (ATL) and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). While there are currently no FDA-approved drugs targeting gp21, it is a major focus for the development of fusion inhibitors, such as synthetic peptides (e.g., P-400), and neutralizing monoclonal antibodies (PubMed: 11967321). These therapeutic strategies aim to prevent the spread of the virus and the progression of associated diseases by blocking the critical membrane fusion step. The high conservation of gp21 across different viral strains makes it an attractive target for broad-spectrum intervention, although the virus's reliance on cell-to-cell transmission presents a significant challenge for traditional neutralizing agents.

Other names

Transmembrane glycoprotein gp21TM subunitHTLV-1 gp21Envelope glycoprotein gp62HTLV-1 Env TM

Fusion inhibition by preventing the transition of the gp21 subunit from a pre-fusion to a post-fusion hairpin conformation, thereby blocking the merger of viral and host cell membranes.