The Selection of RNA Aptamers against S100 Calcium Binding Protein B for Inhibition of Inflammatory Cytokines in Alzheimer’s.

The full proposal can be seen here

Progress Report 1 can be seen here
Progress Report 2 can be seen here

Final Report can be seen here

S100B is a calcium binding protein produced mainly by glial cells in the Central Nervous System (1). As calcium binds to the EF-hands of the protein, S100B undergoes different conformational changes, allowing the protein to bind to several other molecules in the body, making it a multi-functional target (2). Because of the variety of binding capabilities for S100B, these proteins participate in several neurological diseases including Alzheimer’s, epilepsy, schizophrenia, Down’s syndrome, and melanoma (3).

Alzheimer’s disease (AD) is the predominant form of dementia, where patients suffer from a decline of cognitive functions such as language, personality, and memory (4). S100B plays a substantial role in AD as suggested by the elevated levels of the protein in the brain or CNS after diagnosis. S100B can act intracellularly or can be secreted into the extracellular space of glial cells and act as a cytokine, which binds to nearby cells via receptors (5). S100B activates the Receptor for Advanced Glycation Endproducts (RAGE), an immunoglobulin-like cell surface receptor , and in turn, triggers NF-kB and MEK signaling pathways (6). Although nanomolar concentrations of S100B can have trophic and neuroprotective effects, any over expression of the S100B protein can lead to neuroinflammation, neuronal dysfunction, and cell apoptosis that contributes to the degenerative affects of Alzheimer’s (4).

Figure 1: Signal transduction pathway between S100B/RAGE/ and NF-ĸB.
RAGE is activated initially by S100B, that starts a positive feedback loop to continually trigger S100B proteins that activate NF-ĸB gene transcription which release inflammatory cytokines.

Although elevated levels of S100B can indicate brain trauma and Alzheimer’s, no preventative measures to actually delay the onset of neurological damage have been developed. An aptamer is a sequence of nucleic acid that binds specifically to target molecules, primarily proteins (7). An aptamer selected for S100B protein can potentially be used as both a therapeutic and diagnostic tool in combating Alzheimer’s.

Specific Aim 1: Selection of RNA aptamer against S100B protein High concentrations of S100B in the brain and CNS lead to over stimulation of RAGE leading to neurological damage. The selection of an aptamer for S100B that inhibits binding, either directly or allosterically, to the V domain of RAGE will impede further signal transduction pathways that hinder neurological function. The inhibition of the S100B/RAGE interaction would provide a therapeutic method to slow down the devastating effects of Alsheimer’s.

References
1. Zhang, X.Y., et. Al. (2010) “Increased Serum S100B in never-medicated and medicated Schizophrenic patients.” Journal of Psychiatric Research 10:1-5.

2. Razvanpour, A., and Shaw, G. (2009) “Unique S100 Target protein interactions.” Gen. Phsyiol. Biophys. 28: 39-46.

3. http://en.wikipedia.org/wiki/S100B

4. Leclerc,E., et. al. (2010) “The S100B/RAGE Axis in Alzheimer’s Disease.” Cardiovasc. Psychiatry Neurol. P. 1-20.

5. Huttunen, H. et al. (2000) “Coregulation of Neurite Outgrowth and cell survival by Amphoterin and S100 proteins through Receptor for Advanced Glycation Endproducts (RAGE) Activation.” Journal of Biological Chemistry. 275(51): 40096-40105.

6. Sorci, G. et al. (2003) “S100B inhibits Myogenic differentiation and Myotube formation in a RAGE-independent manner.” Molecular and Cellular Biology. 23(14): 4870-4881.

7. http://en.wikipedia.org/wiki/aptamer

Image: Leclerc,E., et. al. (2010) “The S100B/RAGE Axis in Alzheimer’s Disease.” Cardiovasc. Psychiatry Neurol. P. 1-20.

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