Home | Help | Feedback | Subscriptions | Archive | Search | Table of Contents

This Article Full Text (PDF, 1020K) PPT slides of all figures Alert me when this article is cited Services Email this article Similar articles in this journal Alert me to new content in the JCB Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Leslie, M. Search for Related Content PubMed Articles by Leslie, M. Related Collections Related Article Social Bookmarking                            What's this?

Caching killer carbs

Laforin (green) dephosphorylates starch granules in this red alga.

Plants and protists may not have a nervous system, but they can help elucidate the mechanism of a fatal neurodegenerative disease, as Gentry et al. reveal on page 477. The organisms helped researchers pin down the function of a protein suspected of sparking destructive carbohydrate accumulations.

Lafora disease is a fatal form of epilepsy whose symptoms usually begin between the ages of 10 and 20. In neurodegenerative diseases such as Parkinson's and Alzheimer's, globs of insoluble proteins amass in neurons. But in Lafora disease, neurons harbor clumps of insoluble carbohydrates similar to amylopectin, a component of starch. Several mutations can trigger the illness, including glitches in the gene for laforin. This protein carries two key modules: one that grabs carbohydrates, and a second that slices off phosphate groups. Although mouse models develop the symptoms of Lafora disease, researchers still don't understand how their faulty laforin protein elicits neurological damage.

Gentry et al. thus went hunting for other laforin-making organisms. They trolled protist genomes and pinpointed genes for laforin in organisms as different as the pathogen behind toxoplasmosis and a type of red alga. Previously, researchers had thought that only vertebrates manufacture the protein. Like human laforin, the protist version grips carbohydrates and lops off a phosphate. Where laforin hangs out has been a mystery, but the researchers determined that, in one type of protist, it congregates around starch granules.

The team also found that plants carry an unrelated protein with the same function, known as SEX4. Arabidopsis plants with a defective form of SEX4 built up excess starch. The presence of proteins with the same job in such a range of organisms suggests that phosphate removal is crucial for breaking down insoluble carbohydrates. Why persistent phosphates lead to carbohydrate buildup remains unclear. The scientists now want to investigate whether the carb clusters from patients with Lafora disease carry excess phosphates.

Mitch Leslie

mitchleslie{at}comcast.net

CiteULike    Complore    Connotea    Del.icio.us    Digg    Facebook    Reddit    Technorati    Twitter    What's this?

Related Article

The phosphatase laforin crosses evolutionary boundaries and links carbohydrate metabolism to neuronal disease

Matthew S. Gentry, Robert H. Dowen, III, Carolyn A. Worby, Seema Mattoo, Joseph R. Ecker, and Jack E. Dixon
J. Cell Biol. 2007 178: 477-488. [Abstract] [Full Text] [PDF]

This Article Full Text (PDF, 1020K) PPT slides of all figures Alert me when this article is cited Services Email this article Similar articles in this journal Alert me to new content in the JCB Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Leslie, M. Search for Related Content PubMed Articles by Leslie, M. Related Collections Related Article Social Bookmarking                            What's this?