Glycogen ubiquitination pathway

The glycogen ubiquitination pathway is a regulatory system essential for controlling glycogen structure and preventing the accumulation of insoluble glucose polymers. The pathway is primarily mediated by the Malin-Laforin complex, where Laforin (a dual-specificity phosphatase) recruits Malin (an E3 ubiquitin ligase) to glycogen particles (UniProt P0C1P7, O95278). Malin then ubiquitylates various enzymes involved in glycogen metabolism, such as glycogen synthase (GYS1) and protein targeting to glycogen (PTG/PPP1R3C), leading to their regulation or proteasomal degradation (Gentry et al., 2018). Dysregulation of this pathway, typically due to mutations in the EPM2A or NHLRC1 genes, results in the formation of toxic polyglucosan aggregates called Lafora bodies. These aggregates cause progressive neurodegeneration, manifesting as Lafora disease, a severe form of epilepsy (Nitschke et al., 2018). Current therapeutic research focuses on modulating this pathway by inhibiting glycogen synthesis or utilizing enzyme replacement therapies to clear existing aggregates. Drugs like metformin and antisense oligonucleotides are being investigated to mitigate the pathological consequences of pathway failure (Zhou et al., 2022).

Other names

Laforin-Malin complexNHLRC1-EPM2A pathwayPolyglucosan regulation pathwayGlycogen metabolic regulation complex

The primary mechanisms include the inhibition of glycogen synthase (GYS1) to prevent the formation of insoluble polyglucosans, the use of antibody-enzyme fusions to degrade existing Lafora bodies, and the repurposing of metabolic modulators like metformin to reduce glycogen accumulation (Gentry et al., 2018; Nitschke et al., 2018).