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Proc Natl Acad Sci U S A. 2005 Jun 14;102(24):8501-6. Epub 2005 Jun 1.

Insights into Lafora disease: malin is an E3 ubiquitin ligase that ubiquitinates and promotes the degradation of laforin.

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1
Department of Pharmacology, School of Medicine, University of California at San Diego, La Jolla, CA 92093-0721, USA.

Abstract

Lafora disease (LD) is a fatal form of progressive myoclonus epilepsy caused by recessive mutations in either a gene encoding a dual-specificity phosphatase, known as laforin, or a recently identified gene encoding the protein known as malin. Here, we demonstrate that malin is a single subunit E3 ubiquitin (Ub) ligase and that its RING domain is necessary and sufficient to mediate ubiquitination. Additionally, malin interacts with and polyubiquitinates laforin, leading to its degradation. Missense mutations in malin that are present in LD patients abolish its ability to polyubiquitinate and signal the degradation of laforin. Our results demonstrate that laforin is a physiologic substrate of malin, and we propose possible models to explain how recessive mutations in either malin or laforin result in LD. Furthermore, these data distinguish malin as an E3 Ub ligase whose activity is necessary to prevent a neurodegenerative disease that involves formation of nonproteinacious inclusion bodies.

PMID:
15930137
PMCID:
PMC1150849
DOI:
10.1073/pnas.0503285102
[Indexed for MEDLINE]
Free PMC Article
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