Post-translational Modification Defect in Muscular Dystrophy

Post-translational Modification Defect in Muscular Dystrophy

Glycosylation is an essential post-translational modification that underlies many biological processes and diseases.

α-dystroglycan (α-DG) is a receptor for matrix and synaptic proteins that causes muscular dystrophy and lissencephaly upon its abnormal glycosylation (α-dystroglycanopathies).

Researchers identify the glycan unit ribitol 5-phosphate (Rbo5P), a phosphoric ester of pentose alcohol, in α-DG. Rbo5P forms a tandem repeat and functions as a scaffold for the formation of the ligand-binding moiety.

They show that enzyme activities of three major α-dystroglycanopathy-causing proteins are involved in the synthesis of tandem Rbo5P.

Isoprenoid synthase domain-containing (ISPD) is cytidine diphosphate ribitol (CDP-Rbo) synthase. Fukutin and fukutin-related protein are sequentially acting Rbo5P transferases that use CDP-Rbo. Consequently, Rbo5P glycosylation is defective in α-dystroglycanopathy models.

Supplementation of CDP-Rbo to ISPD-deficient cells restored α-DG glycosylation.

These findings establish the molecular basis of mammalian Rbo5P glycosylation and provide insight into pathogenesis and therapeutic strategies in α-DG-associated diseases.