| GABARAPL2, also known as GATE-16, belongs to the mammalian Atg8 protein family and specifically functions within the GABARAP subfamily, which is distinguished from the LC3 subfamily by unique interaction partners and stage-specific roles in autophagy. The protein adopts a ubiquitin-like fold and undergoes post-translational processing wherein the cysteine protease ATG4 cleaves the carboxyl terminus to expose a glycine residue, which then becomes conjugated to phosphatidylethanolamine on autophagosomal membranes through a cascade involving the E1-like enzyme ATG7 and the E2-like enzyme ATG3. GABARAPL2 orchestrates multiple distinct cellular pathways through its capacity to interact with diverse protein partners, functioning both within and beyond conventional autophagy. The protein directly binds N-ethylmaleimide-sensitive factor (NSF) and stimulates its ATPase activity, which subsequently enhances NSF association with the Golgi v-SNARE GOS-28, thereby coupling NSF enzymatic function with SNARE activation to regulate intra-Golgi membrane transport. Within the autophagy pathway, GABARAPL2 operates at a temporally distinct phase compared to LC3 proteins—while LC3 family members facilitate early phagophore membrane elongation, GABARAPL2 and its subfamily members execute critical functions during late-stage autophagosome maturation and fusion with lysosomes, ensuring cargo clearance. GABARAPL2 associates with cargo receptors through LC3-interacting region (LIR) motifs on partner proteins, including the selective autophagy receptor p62/SQSTM1, enabling targeted degradation of ubiquitinated protein aggregates. The protein exhibits specialized functionality in mitophagy, maintaining mitochondrial quality control through selective elimination of damaged mitochondria, which regulates cellular energy homeostasis and prevents excessive reactive oxygen species accumulation. Beyond autophagy, GABARAPL2 mediates antimicrobial defense by specifically associating with the small GTPase ADP-ribosylation factor 1 (Arf1) to promote uniform cytosolic distribution of interferon-inducible GTPases, and loss of GABARAPL2 impairs Arf1 activation, causing interferon-inducible GTPase aggregation and compromising clearance of intracellular pathogens such as Toxoplasma. The protein further participates in endoplasmic reticulum remodeling through interaction with the reticulophagy receptor TEX264, facilitating ER subdomain conversion into autophagosomes during nutrient stress. GABARAPL2 also localizes at the ER through binding the long-chain-fatty-acid-CoA ligase ACSL3, anchoring the ubiquitin-like modifier activating enzyme UBA5 and functionally coupling lipid droplet biogenesis with UFM1-mediated ufmylation pathways. Additionally, GABARAPL2 activates the CUL3(KBTBD6/7) E3 ubiquitin ligase complex locally, promoting ubiquitination and degradation of TIAM1, a guanyl-nucleotide exchange factor for RAC1, thereby influencing cytoskeletal organization, cell migration, and proliferation. Dysregulation of GABARAPL2 expression or function associates with impaired autophagy flux and defective antimicrobial responses, and the protein's multifunctional nature positions it as a regulatory hub integrating membrane trafficking, autophagy, immune defense, and metabolic signaling. |
Lane 1: A20, Lane 2: COS-7, Lane 3: RD, Lane 4: C6
