Loss of c-Cbl RING finger function results in high-intensity TCR signaling and thymic deletion.
Signaling from the T-cell receptor (TCR) in thymocytes is negatively regulated by the RING finger-type ubiquitin ligase c-Cbl. To further investigate this regulation, we generated mice with a loss-of-function mutation in the c-Cbl RING finger domain. These mice exhibit complete thymic deletion by young adulthood, which is not caused by a developmental block, lack of progenitors or peripheral T-cell activation. Rather, this phenotype correlates with greatly increased expression of the CD5 and CD69 activation markers and increased sensitivity to anti-CD3-induced cell death. Thymic loss contrasts the normal fate of the c-Cbl-/- thymus, even though thymocytes from both mutant mice show equivalent enhancement in proximal TCR signaling, Erk activation and calcium mobilization. Remarkably, only the RING finger mutant thymocytes show prominent TCR-directed activation of Akt. We show that the mutant c-Cbl protein itself is essential for activating this pathway by recruiting the p85 regulatory subunit of PI 3-kinase. This study provides a unique model for analyzing high-intensity TCR signals that cause thymocyte deletion and highlights multiple roles of c-Cbl in regulating this process.
Thien
Christine B F
CB
School of Surgery and Pathology, University of Western Australia, Crawley, Australia.
Blystad
Frøydis D
FD
Zhan
Yifan
Y
Lew
Andrew M
AM
Voigt
Valentina
V
Andoniou
Christopher E
CE
Langdon
Wallace Y
WY
D019943:Amino Acid Substitution; D000818:Animals; D015703:Antigens, CD / Q000032:analysis; D000945:Antigens, Differentiation, T-Lymphocyte / Q000032:analysis; D017209:Apoptosis; D017252:CD3 Complex / Q000032:analysis; D018956:CD5 Antigens / Q000032:analysis; D048049:Extracellular Signal-Regulated MAP Kinases / Q000032:analysis; D037181:Lectins, C-Type; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000032:analysis; D051379:Mice; D008822:Mice, Transgenic; D009154:Mutation; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D017434:Protein Structure, Tertiary; D050721:Proto-Oncogene Proteins c-cbl / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D011948:Receptors, Antigen, T-Cell / Q000276:immunology / Q000502:physiology*; D015398:Signal Transduction; D013950:Thymus Gland / Q000276:immunology*; D000099192:CD69 Antigens
D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D017252:CD3 Complex; D018956:CD5 Antigens; D048049:Extracellular Signal-Regulated MAP Kinases; D037181:Lectins, C-Type; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D019869:Phosphatidylinositol 3-Kinases; D050721:Proto-Oncogene Proteins c-cbl; D011948:Receptors, Antigen, T-Cell; D000099192:CD69 Antigens; C493849:Cbl protein, mouse