ATG9B
Domain
Forms a homotrimer with a solvated central pore, which is connected laterally to the cytosol through the cavity within each protomer. Acts as a lipid scramblase that uses its central pore to function: the central pore opens laterally to accommodate lipid headgroups, thereby enabling lipid flipping and redistribution of lipids added to the outer leaflet of ATG9B-containing vesicles, thereby enabling growth into autophagosomes.
The tyrosine-based sorting signal motif, also named YXX-psi motif, promotes interaction with the AP-4 complex.
Function
Phospholipid scramblase involved in autophagy by mediating autophagosomal membrane expansion. Cycles between the preautophagosomal structure/phagophore assembly site (PAS) and the cytoplasmic vesicle pool and supplies membrane for the growing autophagosome. Lipid scramblase activity plays a key role in preautophagosomal structure/phagophore assembly by distributing the phospholipids that arrive through ATG2 (ATG2A or ATG2B) from the cytoplasmic to the luminal leaflet of the bilayer, thereby driving autophagosomal membrane expansion (By similarity). In addition to autophagy, also plays a role in necrotic cell death (By similarity).
Sequence Similarities
Belongs to the ATG9 family.
Tissue Specificity
Highly expressed in placenta (trophoblast cells) and pituitary gland. Not expressed in vascular endothelial.
Cellular localization
- Preautophagosomal structure membrane
- Multi-pass membrane protein
- Under amino acid starvation or rapamycin treatment, redistributes from a juxtanuclear clustered pool to a dispersed peripheral cytosolic pool (PubMed:18936157). The starvation-induced redistribution depends on ULK1 and ATG13 (PubMed:18936157).
Alternative names
APG9L2, NOS3AS, ATG9B, Autophagy-related protein 9B, APG9-like 2, Nitric oxide synthase 3-overlapping antisense gene protein, Protein sONE