SAR1B

The protein encoded by this gene is a small GTPase that acts as a homodimer. The encoded protein is activated by the guanine nucleotide exchange factor PREB and is involved in protein transport from the endoplasmic reticulum to the Golgi. This protein is part of the COPII coat complex. Defects in this gene are a cause of chylomicron retention disease (CMRD), also known as Anderson disease (ANDD). Two transcript variants encoding the same protein have been found for this gene.

Full Name

Secretion Associated Ras Related GTPase 1B

Function

GTP-binding protein involved in transport from the endoplasmic reticulum to the Golgi apparatus (By similarity).
Activated by the guanine nucleotide exchange factor PREB (By similarity).
Involved in the selection of the protein cargo and the assembly of the COPII coat complex (By similarity).
Synergizes with the cargo receptor SURF4 to mediate the export of lipoproteins from the endoplasmic reticulum, thereby regulating lipoprotein delivery and the maintenance of lipid homeostasis (PubMed:33186557).

Biological Process

Biological Process antigen processing and presentation of peptide antigen via MHC class ITAS:Reactome
Biological Process endoplasmic reticulum to Golgi vesicle-mediated transportManual Assertion Based On ExperimentIBA:GO_Central
Biological Process intracellular protein transportManual Assertion Based On ExperimentIBA:GO_Central
Biological Process lipid homeostasisManual Assertion Based On ExperimentIDA:UniProtKB
Biological Process lipoprotein transportManual Assertion Based On ExperimentIDA:UniProtKB
Biological Process membrane organizationManual Assertion Based On ExperimentIBA:GO_Central
Biological Process positive regulation of protein exit from endoplasmic reticulumManual Assertion Based On ExperimentIBA:GO_Central
Biological Process regulation of COPII vesicle coatingManual Assertion Based On ExperimentIBA:GO_Central
Biological Process regulation of lipid transportManual Assertion Based On ExperimentIDA:UniProtKB
Biological Process vesicle organizationManual Assertion Based On ExperimentIBA:GO_Central

Cellular Location

Endoplasmic reticulum membrane
Golgi apparatus, Golgi stack membrane
Associated with the endoplasmic reticulum and Golgi stacks, in particular in the juxta-nuclear Golgi region.

Involvement in disease

Chylomicron retention disease (CMRD):
An autosomal recessive disorder of severe fat malabsorption associated with failure to thrive in infancy. The condition is characterized by deficiency of fat-soluble vitamins, low blood cholesterol levels, and a selective absence of chylomicrons from blood. Affected individuals accumulate chylomicron-like particles in membrane-bound compartments of enterocytes, which contain large cytosolic lipid droplets.