Nucleic Acid Aptamer Selection against Tau Microtubule-Associated Protein
Tau proteins are expressed by functional neurons and oligodendrocytes to stabilize microtubules. They generally consist of two main binding domains: a projection domain that interacts with neural plasma membrane and cytoskeletal elements, and the microtubules binding domain, which is responsible for microtubule polymerization and stabilization. Six main isoforms of tau exist, differing in their number of binding sites due to alternative splicing of exons.
Hyperphosphorylation of the tau protein leads to the self-assembly of neurofibrillary tangles as excessive binding pairs helical and straight filaments together. Neurofibrillary tangles are responsible for a specific class of neurodegenerative diseases that includes Alzheimer's and Parkinson's disease: tauopathy. Aggregation of hyperphosphorylated tau protein accumulates in the brain, leading to apoptosis of neurons.
One approach to inhibiting this process incorporates nucleic acid ligands called aptamers. Aptamers bind with high specificity and high affinity to proposed protein targets for diagnostic and therapeutic purposes. An aptamer against Tau protein could potentially either prevent the formation of neurofibrillary tangles prominent in neurodegenerate diseases or as a diagnostic tool allowing for the early detection of mutated tau protein. Figure 1 depicts tangled clumps of Tau proteins, leading to disintegrating microtubules.
Figure 1: As clumps of Tau proteins tangle together, microtubule subunits deteriorate.
Tau protein can be ordered online through the company rPeptide. The catalog number for my proposed target is T-1005-1. This specific isomer of the protein contains only the binding domain responsible for supporting microtubules. Choosing the protein with the least binding sites allows for greater specificity when selecting for an aptamer. Ordering a 100ug aliquot of the target protein costs approximately $375 and can be ordered by reaching this number: (678) 753-0747.
Huang, Austin. "The Effect of a ΔK280 Mutation on the Unfolded State of a
Microtubule-Binding Repeat in Tau." Computational Biology. Public Library
of Science, 22 Aug. 2008. Web.
"rPeptide Data Sheet." rPeptide. Web.
"Tau Protein in Alzheimers Disease." Edinformatics -- Education for the Information Age. 2009. Web.
www.edinformatics.com/news/tau_protein.htm>.
This is the link for my Research Proposal.
This is the link for my first Progress Report.
Here is my final research paper, outlining the progress on my selection for this semester.
8 comments:
Best of luck! This was my selection project a couple years ago. Tau was way more expensive back then.
Very good idea! I have one question though. If the aptamers target clumps of Tau, wouldn't they also attack functional Tau proteins and affect microtubule stability in the end?
Hi Santiago,
I'm glad that you asked, because I am still working the final kinks out of my scientific design.
My hope is to purchase functional Tau protein, and then to induce hyper-phosphorylation before starting my rounds of selection. This way an aptamer would bind to the phosphorylated segments and prevent tau protein from binding together. If all goes well, the aptamer will not bind to the functional domain of the protein responsible for interacting with the microtubules.
After listening to your presentation yesterday, I was understanding more of how the Tau proteins are affected and can cause neural problems. Microtubules are definitely an essential component to all body cells, both for active transport and cellular division, but could this lead to brain cancer? If an aptamer is found for this, Santiago mentioned that it could impact normal Tau proteins, and may have some side effects to the treatment. Hope to hear more about this!
Hi Shaan,
I'm not quite sure I understand what you mean...
Are you suggesting an aptamer that selectively binds to Tau protein would cause cancer? If I may, I think you are confusing neurofibrillary tangles with malignant tumors. These tangles are proteins-not cells.
Your presentation on this was very interesting, and I cannot wait to see how this will turn out!! Good luck Stephanie!!!
This is a really interesting idea that could definitely lead somewhere. I think the induced hyper-phosphorylation of tau before selection is a good idea, but how does this create tau clumps? Looking into how the proteins bind together might be a good idea (like is there a specific site?) because that's obviously your area of interest. Is there any way you can design your selection conditions in order to make sure it binds to the right binding site and no others?
My intent was to order Tau protein with only the specific binding sites for hyper-phosphorylation. This would ensure that I am only selecting for an aptamer that can competitively bind to these sites. Another option I was considering would be selecting for tau that was already hyper-phosphorylated. Then after inducing phosphorylation,the aptamer could bind to these regions to prevent clumping that leads to tangles. However, I am not sure what directly caused the protein to hyper-phosphorylate, therefore I cannot induce this as I originally planned.
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