exocystmediated

Exocyst-mediated refers to the actions of the exocyst complex in tethering post-Golgi secretory vesicles to the plasma membrane to promote exocytosis. It supports targeted delivery of membrane and secreted proteins, enabling polarized secretion in diverse cell types.

The exocyst is an evolutionarily conserved octameric complex. In budding yeast Saccharomyces cerevisiae the subunits are Sec3, Sec5, Sec6, Sec8, Sec10, Sec15, Exo70, and Exo84. Mammals possess homologs: EXOC1–EXOC8 plus Exo70 and Exo84; specifics vary by organism.

The exocyst is recruited to membranes by small GTPases such as the Rho/Rac/Cdc42 family and by Rab proteins, and by phosphoinositides like PI(4,5)P2. It tethers secretory vesicles at defined plasma membrane sites, facilitating SNARE-mediated fusion with cytoskeletal coordination.

In yeast, exocyst-mediated tethering supports polarized growth at the budding site. In plants, it participates in polarized secretion during tip growth and cell wall formation. In animal cells, it contributes to neuronal synapse formation and function, epithelial polarity, and directed secretion during migration.

Exocyst activity is regulated through assembly dynamics, post-translational modifications, and interactions with cytoskeletal elements. Its proper function is essential for membrane expansion, secretion, and morphogenesis; defects are associated with developmental disorders and disease processes.