Exo70

Exo70 is a protein component of the exocyst, a conserved eight-subunit complex that mediates tethering of secretory vesicles to the plasma membrane before SNARE-mediated fusion. The exocyst complex comprises Sec3, Sec5, Sec6, Sec8, Sec10, Sec15, Exo70, and Exo84, and Exo70 provides a primary interface for membrane targeting and vesicle docking.

In cellular trafficking, Exo70 helps recruit the exocyst to sites of secretion and interacts with small GTPases such as RalA and RalB, among others. These interactions help direct polarized exocytosis to specific plasma membrane regions, supporting processes like directional growth, membrane remodeling, and the trafficking of membrane proteins and receptors. Exo70’s activity influences secretion in diverse cell types, including epithelial cells, neurons, and migrating cells, and can affect nutrient transporter trafficking such as GLUT4 in adipocytes.

In vertebrates, Exo70 is encoded by the EXOC7 gene. The Exo70 family is expanded in higher eukaryotes, with multiple Exo70-like paralogs across plants and animals, reflecting diversification of exocyst function. These paralogs can form alternative exocyst assemblies and may exhibit tissue- or process-specific roles, contributing to the regulation and specificity of exocytosis in different cellular contexts.

Regulation of Exo70 occurs through its interactions with other exocyst subunits and with regulatory proteins, as well as post-translational modifications that influence localization and vesicle docking efficiency. Overall, Exo70 acts as a key determinant of where exocytosis occurs, underpinning cellular polarity, secretion, and membrane trafficking.