Syndecan-1 increases B-lymphoid cell extravasation in response to HIV-1 Tat via α_vβ₃/pp60src/pp125FAK pathway

Area of Science:

• Molecular Biology
• Immunology
• Virology

Background:

• Syndecan-1, a heparan sulfate proteoglycan, is often overexpressed in AIDS-related B lymphoid malignancies.
• The HIV-1 transactivating factor (Tat) plays a key role in AIDS-related lymphoma (ARL) pathogenesis by interacting with cell surface molecules.
• Understanding the role of syndecan-1 in Tat-mediated cell migration is crucial for ARL progression.

Purpose of the Study:

• To investigate the role of syndecan-1 in mediating the migration of B lymphoid cells in response to HIV-1 Tat.
• To elucidate the signaling pathways involved in Tat-induced B lymphoid cell migration, with and without syndecan-1 overexpression.

Main Methods:

• Comparison of B-lymphoid Namalwa cell clones with and without syndecan-1 overexpression (EV-Ncs and SYN-Ncs) for Tat responsiveness.
• Analysis of signaling pathways including CXCR4, G-proteins, Rac, pp60src, and pp125FAK phosphorylation.
• Assessment of integrin engagement (αvβ3) and syndecan-1 interactions with Tat, pp60src, and αvβ3.

Main Results:

• In the absence of syndecan-1, Tat induces limited migration via CXCR4, G-proteins, and Rac.
• Syndecan-1 overexpression enhances Tat-induced migration, shifting the pathway to be independent of CXCR4/G-protein and dependent on pp60src phosphorylation.
• Tat-induced migration and pp60src phosphorylation require αvβ3 integrin engagement and pp125FAK phosphorylation, mediated by a syndecan-1/αvβ3/pp60src complex.

Conclusions:

• Syndecan-1 overexpression significantly increases B lymphoid cell migration in response to Tat.
• This enhanced migration is driven by a switch in signaling pathways from CXCR4/G-protein/Rac to a syndecan-1/αvβ3/pp60src/pp125FAK cascade.
• The findings highlight the critical role of the Tat/syndecan-1/αvβ3 interplay in ARL progression and suggest potential therapeutic targets.