3BP2 has been previously described as the protein mutated in the osteoporotic disorder, Cherubism. The gain of function mutation that characterizes Cherubism is the result of an uncoupling of its interaction with Tankyrase 2, which has been reported to stimulate 3BP2 ubiquitination. Here we describe an attempt at identifying the E3 ligase responsible for mediating this ubiquitination using four candidate members from the Nedd4 family. Based on their respective abilities to bind and ubiquitinate 3BP2, as well as their sensitivity to the presence of Tankyrase 2 and to 3BP2 mutations (including Cherubism mutations and mutations within the 3BP2 PPxY motif thought to confer binding to the Nedd4 proteins), we have determined that Smurf1 best fits our model. Further supporting these findings, we have seen an elevation in 3BP2 protein levels in macrophages derived from Smurf1-/-/Smurf2+/- mice. This work supports a role for the Nedd4 family member, Smurf1, in mediating 3BP2 ubiquitination.

3BP2 has been previously described as the protein mutated in the osteoporotic disorder, Cherubism. The gain of function mutation that characterizes Cherubism is the result of an uncoupling of its interaction with Tankyrase 2, which has been reported to stimulate 3BP2 ubiquitination. Here we describe an attempt at identifying the E3 ligase responsible for mediating this ubiquitination using four candidate members from the Nedd4 family. Based on their respective abilities to bind and ubiquitinate 3BP2, as well as their sensitivity to the presence of Tankyrase 2 and to 3BP2 mutations (including Cherubism mutations and mutations within the 3BP2 PPxY motif thought to confer binding to the Nedd4 proteins), we have determined that Smurf1 best fits our model. Further supporting these findings, we have seen an elevation in 3BP2 protein levels in macrophages derived from Smurf1-/-/Smurf2+/- mice. This work supports a role for the Nedd4 family member, Smurf1, in mediating 3BP2 ubiquitination.

3BP2 was originally identified through its interaction with the ABL kinase. Fusion of ABL with the BCR gene forms the BCR-ABL onco-protein, which is causative in Chronic Myeloid Leukemia (CML) and acute lymphoid leukemia (ALL). Due to the ability of 3BP2 to regulate ABL activity in osteoblasts, we hypothesize that 3BP2 modulates BCR-ABL signalling. Overexpression of 3BP2 in the CML-T1 cell line produced a marked decrease in global tyrosine phosphorylation. 3BP2 overexpression also resulted in a significant increase in CML-T1 cell growth, accompanied by altered ERK1/2, AKT, SYK, LYN, HCK, and CBL phosphorylation and expression. A phospho-SRC family protein and a 116 kDa phospho-protein were identified as 3BP2 interaction partners in response to BCR-ABL activation. BCR-ABL bone marrow transplantation (BMT) models in 3bp2-/- mice exhibit accelerated disease compared to wild-type mice, with altered leukemic phenotype. In conclusion, 3BP2 is able to modulate signalling through BCR-ABL and affect BCR-ABL-induced disease outcome.

3BP2 was originally identified through its interaction with the ABL kinase. Fusion of ABL with the BCR gene forms the BCR-ABL onco-protein, which is causative in Chronic Myeloid Leukemia (CML) and acute lymphoid leukemia (ALL). Due to the ability of 3BP2 to regulate ABL activity in osteoblasts, we hypothesize that 3BP2 modulates BCR-ABL signalling. Overexpression of 3BP2 in the CML-T1 cell line produced a marked decrease in global tyrosine phosphorylation. 3BP2 overexpression also resulted in a significant increase in CML-T1 cell growth, accompanied by altered ERK1/2, AKT, SYK, LYN, HCK, and CBL phosphorylation and expression. A phospho-SRC family protein and a 116 kDa phospho-protein were identified as 3BP2 interaction partners in response to BCR-ABL activation. BCR-ABL bone marrow transplantation (BMT) models in 3bp2-/- mice exhibit accelerated disease compared to wild-type mice, with altered leukemic phenotype. In conclusion, 3BP2 is able to modulate signalling through BCR-ABL and affect BCR-ABL-induced disease outcome.