Caspase cleavage of Itch in chronic lymphocytic leukemia cells.
E3 ubiquitin ligases catalyze the final step in the ubiquitylation cascade and therefore determine the specificity of this important cellular metabolic pathway. Although first thought to be constitutively active, increasing evidence demonstrates the existence of a wide variety of posttranslational modifications that regulate the activity of these enzymes. Here we show that upon induction of apoptosis the ubiquitin ligase Itch is processed by caspases both in vitro and ex vivo in cells from patients with chronic lymphocytic leukemia (CLL). The specific cleavage site was mapped to residue Asp240. Interestingly, cleavage of Itch by active caspases does not inhibit the catalytic activity of Itch, but results in the loss of an N-terminal Itch fragment that contains a negative regulatory region. Our data suggests that caspase-dependent Itch cleavage might be an important regulator of Itch at the endogenous level under both physiological and stressed conditions.
Rossi
Mario
M
Medical Research Council, Toxicology Unit, Hodgkin Building, University of Leicester, Lancaster Road, Leicester, UK.
Inoue
Satoshi
S
Walewska
Renata
R
Knight
Richard A
RA
Dyer
Martin J S
MJ
Cohen
Gerald M
GM
Melino
Gerry
G
D017209:Apoptosis; D020169:Caspases / Q000378:metabolism*; D002384:Catalysis; D004791:Enzyme Inhibitors / Q000494:pharmacology; D056572:Histone Deacetylase Inhibitors; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D007211:Indoles; D015451:Leukemia, Lymphocytic, Chronic, B-Cell; D000077767:Panobinostat; D012097:Repressor Proteins / Q000378:metabolism*; D013312:Stress, Physiological; D013379:Substrate Specificity; D014407:Tumor Cells, Cultured; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*
D004791:Enzyme Inhibitors; D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; D007211:Indoles; D012097:Repressor Proteins; C012589:trichostatin A; D000077767:Panobinostat; C432966:ITCH protein, human; D044767:Ubiquitin-Protein Ligases; D020169:Caspases