Sec24D

Sec24D is a member of the Sec23/24 protein family that functions as part of the COPII coat complex involved in protein sorting and transport from the endoplasmic reticulum to the Golgi apparatus. It is encoded by the SEC24D gene located on chromosome 9 in humans. The Sec24D protein is part of the inner coat layer of COPII vesicles and acts as a cargo adaptor, recognizing signal motifs on vesicular cargo proteins and helping to specify which proteins are recruited into budding vesicles. The COPII complex comprises Sec23, Sec24, Sec13, Sec31, and the small GTPase Sar1; Sec24D cooperates with Sec23 in cargo selection and membrane bending.

Variants in SEC24D are associated with osteogenesis imperfecta, a connective-tissue disorder characterized by fragile bones and growth deficiencies. Hypomorphic mutations reduce Sec24D function, impairing secretion of extracellular matrix proteins such as collagen, leading to the clinical features of the disease. Genetic studies have identified several pathogenic mutations, including missense and nonsense alterations throughout the coding sequence. Other reported functions of Sec24D include participation in the secretion of lipidated proteins and diverse transmembrane proteins; it has been shown to interact with SNAREs and membrane-fusion machinery. The protein is highly conserved across vertebrates, indicating an essential role in intracellular trafficking. Research into Sec24D contributes to understanding basic cellular transport mechanisms and the pathogenic basis of skeletal disorders.