Differential subcellular localization regulates c-Cbl E3 ligase activity upon Notch3 protein in T-cell leukemia.
Notch3 and pTalpha signaling events are essential for T-cell leukemogenesis and characterize murine and human T-cell acute lymphoblastic leukemia. Genetic ablation of pTalpha expression in Notch3 transgenic mice abrogates tumor development, indicating that pTalpha signaling is crucial to the Notch3-mediated leukemogenesis. Here we report a novel direct interaction between Notch3 and pTalpha. This interaction leads to the recruitment and persistence of the E3 ligase protein c-Cbl to the lipid rafts in Notch3-IC transgenic thymocytes. Conversely, deletion of pTalpha in Notch3 transgenic mice leads to cytoplasmic retention of c-Cbl that targets Notch3 protein to the proteasomal-degradative pathway. It appears that protein kinase C theta (PKCtheta), by regulating tyrosine and serine phosphorylation of Cbl, is able to control its function. We report here that the increased Notch3-IC degradation correlates with higher levels of c-Cbl tyrosine phosphorylation in Notch3-IC/pTalpha(-/-) double-mutant thymocytes, which also display a decreased PKCtheta activity. Our data indicate that pTalpha/pre-T-cell receptor is able to regulate the different subcellular localization of c-Cbl and, by regulating PKCtheta activity, is also able to influence its ubiquitin ligase activity upon Notch3 protein.
Checquolo
S
S
Department of Experimental Medicine, University Sapienza, Rome 00161, Italy.
Palermo
R
R
Cialfi
S
S
Ferrara
G
G
Oliviero
C
C
Talora
C
C
Bellavia
D
D
Giovenco
A
A
Grazioli
P
P
Frati
L
L
Gulino
A
A
Screpanti
I
I
D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D042541:Intracellular Space / Q000378:metabolism; D007527:Isoenzymes / Q000378:metabolism; D015458:Leukemia, T-Cell / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D021962:Membrane Microdomains / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D008954:Models, Biological; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011485:Protein Binding; D011493:Protein Kinase C / Q000378:metabolism; D000074121:Protein Kinase C-theta; D050721:Proto-Oncogene Proteins c-cbl / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D000071656:Receptor, Notch3; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000235:genetics / Q000378:metabolism; D051880:Receptors, Notch / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D013950:Thymus Gland / Q000378:metabolism / Q000473:pathology; D014162:Transfection; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism
D007527:Isoenzymes; C499373:Notch3 protein, mouse; D000071656:Receptor, Notch3; D016693:Receptors, Antigen, T-Cell, alpha-beta; D051880:Receptors, Notch; D050721:Proto-Oncogene Proteins c-cbl; D044767:Ubiquitin-Protein Ligases; C489593:Prkcq protein, mouse; D011493:Protein Kinase C; D000074121:Protein Kinase C-theta; D046988:Proteasome Endopeptidase Complex