PDZ scaffolds regulate extracellular vesicle production, composition, and uptake.

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Extracellular vesicles (EVs) are crucial for cell-to-cell communication but their biological mechanisms remain incompletely understood.
• PDZ proteins are molecular scaffolds involved in signal transduction and multicellularity.
• Syndecans (SDCs) play a known role in EV biogenesis, loading, and turnover.

Purpose of the Study:

• To investigate the role of PDZ proteins as regulators of EV biology.
• To determine the interactions between PDZ proteins, tetraspanins (CD9, CD63, CD81), and syndecans (SDCs).
• To elucidate the impact of PDZ proteins on EV characteristics and cell surface heparan sulfate.

Main Methods:

• Proteomic analysis to identify PDZ protein interactions with tetraspanins and SDCs.
• Loss-of-function studies of nine PDZ proteins.
• Assessment of tetraspanin and SDC levels, localization, and metabolism.
• Analysis of heparan sulfate levels at the cell surface.

Main Results:

• PDZ proteins directly interact with tetraspanins and extensively with SDCs.
• Loss of PDZ proteins alters tetraspanin and SDC levels, localization, and metabolism.
• PDZ proteins influence endosomal budding and EV accumulation.
• PDZ proteins regulate cell surface heparan sulfate levels involved in EV capture.

Conclusions:

• PDZ proteins are key regulators of EV biology, influencing EV heterogeneity and turnover.
• The interplay between SDCs, tetraspanins, and PDZ proteins forms a critical framework for EV production and intercellular communication.
• Understanding these molecular interactions advances the potential use of EVs in diagnostics and therapeutics.