Cortactin promotes exosome secretion by controlling branched actin dynamics

Area of Science:

• Cell Biology
• Cancer Research
• Extracellular Vesicles

Background:

• Exosomes are extracellular vesicles crucial for intercellular communication and cancer progression.
• The precise mechanisms governing exosome secretion remain largely unknown.
• Cortactin is an actin-binding protein involved in cytoskeletal regulation.

Purpose of the Study:

• To investigate the role of cortactin in regulating exosome secretion.
• To elucidate the molecular mechanisms by which cortactin influences exosome release.
• To determine the functional impact of cortactin-mediated exosome secretion on cancer cell behavior.

Main Methods:

• Cortactin knockdown and overexpression in cancer cells.
• Quantification of exosome secretion and cargo analysis.
• Live-cell imaging to track multivesicular late endosome (MVE) trafficking and docking.
• Biochemical assays to assess cortactin's interaction with the Arp2/3 complex and actin filaments.
• Functional rescue experiments using purified exosomes.

Main Results:

• Cortactin levels directly correlate with exosome secretion rates without affecting exosome cargo.
• Cortactin is essential for MVE trafficking and plasma membrane docking, dependent on its interaction with the Arp2/3 complex and actin.
• Cortactin, Rab27a, and coronin 1b cooperate to stabilize actin-rich MVE docking sites, promoting exosome release.
• Restoring exosome levels rescues serum-independent growth and invasion defects in cortactin-knockdown cells.

Conclusions:

• Cortactin plays a critical role in promoting exosome secretion.
• Cortactin stabilizes actin-rich MVE docking sites, facilitating exosome release.
• Targeting cortactin-mediated exosome secretion may offer a novel therapeutic strategy for cancer.