ATG4D

Autophagy is the process by which endogenous proteins and damaged organelles are destroyed intracellularly. Autophagy is postulated to be essential for cell homeostasis and cell remodeling during differentiation, metamorphosis, non-apoptotic cell death, and aging. Reduced levels of autophagy have been described in some malignant tumors, and a role for autophagy in controlling the unregulated cell growth linked to cancer has been proposed. This gene belongs to the autophagy-related protein 4 (Atg4) family of C54 endopeptidases. Members of this family encode proteins that play a role in the biogenesis of autophagosomes, which sequester the cytosol and organelles for degradation by lysosomes. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Jul 2013]

Autophagy Related 4D Cysteine Peptidase

Cysteine protease ATG4D: Cysteine protease required for the cytoplasm to vacuole transport (Cvt) and autophagy. Cleaves the C-terminal amino acid of ATG8 family proteins MAP1LC3 and GABARAPL2, to reveal a C-terminal glycine. Exposure of the glycine at the C-terminus is essential for ATG8 proteins conjugation to phosphatidylethanolamine (PE) and insertion to membranes, which is necessary for autophagy. Has also an activity of delipidating enzyme for the PE-conjugated forms.
Cysteine protease ATG4D, mitochondrial: Plays a role as an autophagy regulator that links mitochondrial dysfunction with apoptosis. The mitochondrial import of ATG4D during cellular stress and differentiation may play important roles in the regulation of mitochondrial physiology, ROS, mitophagy and cell viability.

Apoptotic process Source: UniProtKB-KW
Autophagy Source: UniProtKB-KW
Protein transport Source: UniProtKB-KW
Proteolysis Source: UniProtKB

Cysteine protease ATG4D: Cytoplasm
Cysteine protease ATG4D, mitochondrial: Mitochondrion matrix; Cytoplasm. Imported into mitochondrial matrix after cleavage by CASP3 during oxidative stress and cell death.

Cleaved by CASP3 during apoptosis which leads to increased activity. The cleavage by CASP3 reveals a cryptic mitochondrial targeting sequence immediately downstream of their canonical caspase cleavage sites which leads to mitochondrial import of the protein.