A model of neurodegeneration

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A model of neurodegeneration

Postby dignan » Thu Jan 29, 2009 8:44 pm

This research could be very important for us if the model of neurodegeneration / axonal degeneration that they have developed applies to MS.

New Pathway is a Common Thread in Age-Related Neurodegenerative Diseases

January 29, 2009 - How are neurodegenerative diseases such as Alzheimer's initiated, and why is age the major risk factor? A recent study of a protein called MOCA (Modifier of Cell Adhesion), carried out at the Salk Institute for Biological Studies, provides new clues to the answers of these fundamental questions.

Under normal circumstances, MOCA is a key member of the squadron charged with keeping Alzheimer's disease at bay. A team of researchers led by Salk professor David Schubert, Ph.D., demonstrated what happens when MOCA goes on furlough. In the process Schubert identified a novel pathway with broad implications for both Alzheimer's and other age-related neurodegenerative diseases.

Their findings, reported in the current issue of the Journal of Neuroscience, show how neurodegenerative disease starts, initiating in the nerve ending and inducing gradual changes, like a chain reaction over a long time. The animal model used in the study also will allow scientists to better understand the processes behind the formation of the protein aggregates that are common to most neurodegenerative diseases. In addition, it will provide new opportunities to target the earliest steps for therapy.

MOCA was initially identified as a protein that binds to presenilin, a molecule that when mutated causes familial Alzheimer's disease. MOCA is only found in neurons and regulates the expression of the beta amyloid protein responsible for the Alzheimer's plaques that are the hallmark of the disease. To better understand MOCA's function, Qi Chen, Ph.D., a senior scientist in Schubert's laboratory, created a line of mice genetically engineered to lack the gene for MOCA.

"Because of the initial studies in cultured cells that we had done, we expected these mice to develop plaques," explains Schubert. "What we found was that they develop ataxia—a motor coordination problem—as they age." Chen then studied the pathology of these mice and found that it reflected a common feature of most age-related neurological diseases, not just Alzheimer's.

The main problem turned out to be the degeneration of axons, the long projections that conduct impulses away from neurons. The axonal degeneration was caused by the accumulation of protein aggregates. Although the mice were not born with the problem, they acquired it, along with the ataxia, as they aged, and the ataxia worsened over time.

for the rest of the article:

Here is the Pubmed abstract:

Loss of modifier of cell adhesion reveals a pathway leading to axonal degeneration.

J Neurosci. 2009 Jan 7;29(1):118-30.
Chen Q, Peto CA, Shelton GD, Mizisin A, Sawchenko PE, Schubert D.
Cellular Neurobiology Laboratory, The Salk Institute for Biological Studies, La Jolla, California 92037, USA.

Axonal dysfunction is the major phenotypic change in many neurodegenerative diseases, but the processes underlying this impairment are not clear. Modifier of cell adhesion (MOCA) is a presenilin binding protein that functions as a guanine nucleotide exchange factor for Rac1.

The loss of MOCA in mice leads to axonal degeneration and causes sensorimotor impairments by decreasing cofilin phosphorylation and altering its upstream signaling partners LIM kinase and p21-activated kinase, an enzyme directly downstream of Rac1. The dystrophic axons found in MOCA-deficient mice are associated with abnormal aggregates of neurofilament protein, the disorganization of the axonal cytoskeleton, and the accumulation of autophagic vacuoles and polyubiquitinated proteins. Furthermore, MOCA deficiency causes an alteration in the actin cytoskeleton and the formation of cofilin-containing rod-like structures. The dystrophic axons show functional abnormalities, including impaired axonal transport. These findings demonstrate that MOCA is required for maintaining the functional integrity of axons and define a model for the steps leading to axonal degeneration.
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