The Small Heat-shock Protein αB-Crystallin Promotes FBX4-dependent Ubiquitination*

By J. den Engelsman, V. Keijsers, W. D. de Jong, W. Boelens. Journal of Biological Chemistry, 2003

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αB-Crystallin is a small heat-shock protein in which three serine residues (positions 19, 45, and 59) can be phosphorylated under various conditions. We describe here the interaction of αB-crystallin with FBX4, an F-box-containing protein that is a component of the ubiquitin-protein isopeptide ligase SCF (SKP1/CUL1/F-box). The interaction with FBX4 was enhanced by mimicking phosphorylation of αB-crystallin at both Ser-19 and Ser-45 (S19D/S45D), but not at other combinations. Ser-19 and Ser-45 are preferentially phosphorylated during the mitotic phase of the cell cycle. Also αB-crystallin R120G, a mutant found to co-segregate with a desmin-related myopathy, displayed increased interaction with FBX4. Both αB-crystallin S19D/S45D and R120G specifically translocated FBX4 to the detergent-insoluble fraction and stimulated the ubiquitination of one or a few yet unknown proteins. These findings implicate the involvement of αB-crystallin in the ubiquitin/proteasome pathway in a phosphorylation- and cell cycle-dependent manner and may provide new insights into the αB-crystallin-induced aggregation in desmin-related myopathy.

Subfields: Cell Biology, Molecular Biology

View Paper: https://www.semanticscholar.org/paper/600d5e088409cd86f28055dd8565b662fda4822f

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Citations in the corpus

The SCF ubiquitin ligase: insights into a molecular machine (2004, background): “pl?Q9UKT5">Fbx4 in a manner that is dependent on the mitotic-specific phosphorylation of certain serines in α-crystalli”
Phosphorylation-Dependent Ubiquitination of Cyclin D1 by the SCFFBX4-αB Crystallin Complex (2006, background): “Phospho-T286 dependent interaction between cyclin D1 and the SCFFBX4-αB crystallin ligase αB crystallin associates with a 46 KD protein, FBX4, in vivo and increases ubiquitinconjugation of unknown proteins (den Engelsman et al., 2003).”