pRb-dependent cyclin D3 protein stabilization is required for myogenic differentiation.

Abstract

The expression of retinoblastoma (pRb) and cyclin D3 proteins is highly induced during the process of skeletal myoblast differentiation. We have previously shown that cyclin D3 is nearly totally associated with hypophosphorylated pRb in differentiated myotubes, whereas Rb-/- myocytes fail to accumulate the cyclin D3 protein despite normal induction of cyclin D3 mRNA. Here we report that pRb promotes cyclin D3 protein accumulation in differentiating myoblasts by preventing cyclin D3 degradation. We show that cyclin D3 displays rapid turnover in proliferating myoblasts, which is positively regulated through glycogen synthase kinase 3beta (GSK-3beta)-mediated phosphorylation of cyclin D3 on Thr-283. We describe a novel interaction between pRb and cyclin D3 that maps to the C terminus of pRb and to a region of cyclin D3 proximal to the Thr-283 residue and provide evidence that the pRb-cyclin D3 complex formation in terminally differentiated myotubes hinders the access of GSK-3beta to cyclin D3, thus inhibiting Thr-283 phosphorylation. Interestingly, we observed that the ectopic expression of a stabilized cyclin D3 mutant in C2 myoblasts enhances muscle-specific gene expression; conversely, cyclin D3-null embryonic fibroblasts display impaired MyoD-induced myogenic differentiation. These results indicate that the pRb-dependent accumulation of cyclin D3 is functionally relevant to the process of skeletal muscle cell differentiation.

• Authors: Francesca De Santa, Sonia Albini, Eleonora Mezzaroma, Livio Baron, Armando Felsani, Maurizia Caruso
• Journal: Molecular and cellular biology (Mol Cell Biol) Vol. 27 Issue 20 Pg. 7248-65 (Oct 2007) ISSN: 0270-7306 [Print] United States
• PMID: 17709384 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Ccnd3 protein, mouse
• Cyclin D3
• Cyclins
• Retinoblastoma Protein
• Threonine
• Glycogen Synthase Kinase 3 beta
• Gsk3b protein, mouse
• Glycogen Synthase Kinase 3

Topics

• Animals
• Cell Differentiation (physiology)
• Cells, Cultured
• Cyclin D3
• Cyclins (genetics, metabolism)
• Glycogen Synthase Kinase 3 (genetics, metabolism)
• Glycogen Synthase Kinase 3 beta
• Mice
• Mice, Knockout
• Muscle Development (physiology)
• Myoblasts (cytology, physiology)
• Phosphorylation
• Retinoblastoma Protein (genetics, metabolism)
• Threonine (metabolism)