ubiquitin-like (Ubl) domain found in gamma-aminobutyric acid receptor-associated protein (GABARAP) and similar proteins; sub-family of the autophagy-related 8 (ATG8) protein family
GABARAP (also termed GABA(A) receptor-associated protein, ATG8A, or MM46) has been implicated in intracellular protein trafficking. It is a cytosolic protein, localized to transport vesicles, the Golgi network and the endoplasmic reticulum. It interacts with the intracellular domain of the gamma2 subunit of GABA(A) receptors, and thus, functions as a trafficking modulator implicated in the intracellular trafficking of GABA(A) receptor. GABARAP also acts as a Ubl modifier belonging to the ATG8 (autophagy-related 8) protein family which is essential for autophagosome biogenesis and maturation. GABARAP recruits phosphatidylinositol 4-kinase II alpha (PI4KIIalpha) as a specific downstream effector, and regulates phosphatidylinositol 4-phosphate (PI4P)-dependent autophagosome lysosome fusion. This sub-family also includes GABARAPL1 (also termed GABA(A) receptor-associated protein-like, or GEC1), GABARAPL2/GATE-16, and GABARAPL3. GABARAPL1 has been involved in the intracellular transport of receptors via interactions with tubulin and GABA(A) or kappa opioid receptors. GABARAPL1 is also a Ubl modifier that functions as a mediator involved in androgen-regulated autophagy process. It is transcriptionally modulated by androgen receptor (AR) and has a repressive role in autophagy. In addition, GABARAPL1 is required for increased membrane expression of epidermal growth factor receptor (EGFR) during hypoxia, suggesting a possible role in the trafficking of these membrane proteins. GABARAPL1 may also play a key role in several important biological processes such as cancer or neurodegenerative diseases. Low expression of GABARAPL1 is associated with poor prognosis of patients with hepatocellular carcinoma.
Jiyao W et al.(2023). "The conserved domain database in 2023.",