HTLV type 1 envelope glycoprotein gp46 evokes necrosis by binding to receptor complex

Area of Science:

• Virology
• Cell Biology
• Molecular Biology

Background:

• Human T-lymphotropic virus type 1 (HTLV-1) causes syncytium formation through interactions involving its envelope protein.
• 71-kDa heat shock cognate protein (HSC70) acts as a receptor, forming a complex with beta-actin and phosphatidylglycerol (PG).

Purpose of the Study:

• To investigate the molecular mechanisms by which HTLV-1 envelope protein induces cell death.
• To identify specific regions of the HTLV-1 envelope protein responsible for receptor interaction and cytotoxicity.

Main Methods:

• Analysis of HTLV-1 and HTLV-2 peptide interactions with cellular components (HSC70, beta-actin, PG).
• Assessment of the cytotoxic effects of viral peptide segments on MOLT-4 cells.
• Determination of cell death mechanisms (necrosis vs. apoptosis).

Main Results:

• The HTLV-1 gp46 envelope protein associates with HSC70, leading to target cell membrane pore formation and subsequent cell death (necrosis).
• A specific peptide segment, gp46-197, binds to HSC70 and PG and exhibits cytotoxicity.
• Other binding sites on gp46 and gp21, interacting only with PG, did not cause cell death.
• HTLV-2 peptides showed different binding properties and lacked cytotoxicity, with significant amino acid alterations in the hydrophilic face of the amphipathic structure compared to HTLV-1.

Conclusions:

• The interaction between HTLV-1 gp46 and HSC70, particularly through the gp46-197 peptide's hydrophilic face, is crucial for inducing pore formation in lipid bilayers.
• This pore formation can lead to membrane fusion or cell death, explaining HTLV-1-induced syncytium formation and cytotoxicity.