SEC31A

SEC31A is a human gene that encodes Sec31A, a large cytosolic protein and a key component of the COPII vesicle coat involved in ER-to-Golgi transport. It is a vertebrate homolog of yeast Sec31 and, together with Sec13, forms the outer coat of COPII vesicles that bud from the endoplasmic reticulum. Sec31A functions as a scaffold that helps organize and stabilize the coat, coordinating with the inner coat formed by Sec23/24 and the small GTPase Sar1 during vesicle formation.

Functionally, Sec31A participates in recruiting and regulating COPII coat assembly at ER exit sites. By interacting with Sec13 and with the inner coat components, Sec31A contributes to vesicle budding, cargo selection, and the efficiency of cargo export from the ER. Its activity is integrated into the broader secretory pathway and is required for effective ER-to-Golgi trafficking. Sec31A localization is primarily at ER exit sites, where COPII assembly occurs, and its presence supports proper coat formation during vesicle budding.

Structure and regulation: SEC31A encodes a large protein enriched in coiled-coil and disordered regions typical of cytoskeletal-like scaffolds. These regions mediate interactions with Sec13 and Sec23, enabling outer-coat assembly. The function of Sec31A is modulated by cellular signals that influence COPII coat dynamics, allowing cells to adjust secretion in response to physiological conditions. The Sec31 family is conserved across eukaryotes, underscoring a fundamental role in the secretory pathway.

Clinical relevance: While COPII components are essential for secretion, specific disease associations with SEC31A variants are not well defined. Research focuses on its role in vesicle formation, cargo trafficking, and ER export efficiency, reflecting its broad importance in constitutive secretion across tissues.