Poster Presentation Worksheet Directions: Write one to two paragraphs for each of the two audiences below that summarizes how you would explain your poster to a visitor. Imagine yourself presenting your poster and giving a two-minute summary of your research to someone; think about how you should adjust your explanation for a general audience versus someone who has more background in your area of research. You will submit this worksheet along with your poster and it will be posted online. 1. Your explanation for a general audience: Alzheimer’s disease (AD) is a neurodegenerative condition resulting in memory loss. According to the Alzheimer’s Association it is estimated that 5.5 million people above the age of 65 are currently living with this disease. Unfortunately, no current treatment targets the underlying pathology of AD. Gamma-secretase is known to be the causative agent of the amyloid- β peptides (Aβ) plaques that build up in the brain. The Aß plaques are made up of the 42 amino acid length Aβ , which is generally thought to be Aβ that causes AD, as shown in Figure 1. Current research is observing the potential effects of the longer forms of Aβ in the pathogenesis of AD. Aß42 plaques ultimately leads to neurofibrillary tangles and loss of function. Gamma-secretase is a membrane protease that has over 90 substrates, including Notch, which is a part of a signaling pathway involved in many important cellular functions. Inhibitors of gamma-secretase cause toxic off- target side effects, thought to be due to unwanted targeting of Notch. Gamma- secretase modulators (GSM), which do not inhibit gamma-secretase, but rather modulate its function are currently being developed and tested towards an ultimate goal of an effective AD therapy. Compounds were derived from the parent compound, GSM-4, (bottom left corner) by Sanjay Bhattarai. These different analogs were tested in: human embryonic kidney (HEK) cells with a familial AD mutation known as the Swedish mutation (notated as NL), human neuroblastoma cells (SH-SY5Y) with the Swedish mutation and the Arctic mutation (notated as G) with various phenylalanine mutations (notated as F) designed to alter gamma-secretase generation of Aβ s. After treating a cell line for 24-hours with a GSM, the media was collected and the protein composition for Aß of different lengths was measured. Lei Liu, Chad Pope, and I handled the cell culture, GSM treatments, and worked to generate the ELISA data as shown by the figures on the right. As you can see from the graphs, these structures have varying effects on the levels of Aβ peptides based on their structural modifications. Ideally the smaller and more soluble Aßs would increase indicating the GSM increases trimming of Aβ s. In conclusion, SB-303 was found to stimulate production of Aß37 while keeping the production of Aß40 and Aß42 at the homeostatic level of production. Therefore, the levels of longer Aβ s (>43)
must be decreased. Current research suggests these longer forms of Aβ may be linked to AD. SB-303 will be used for further development of GSM analogs. 2. Your explanation for a professor from your department: Alzheimer’s disease (AD) currently has limited treatment options, of which all lose efficacy over time. Gamma-secretase modulators (GSM) may lead to an AD therapy that treats the underlying pathology of AD. Gamma-secretase is a proteolytic membrane protein with over ninety known substrates, including Notch, a transmembrane protein which is a part of a signaling pathway involved in many important cellular functions. Early development of AD treatments found that full antagonists of gamma-secretase causes toxic off-target effects in patients, which are mostly attributed to modulation of Notch. Therefore, GSMs, which are selective for gamma-secretase processing of amyloid precursor protein, have been pursued as a pharmacological therapy in AD research. It is known that the Aß42 (42 amino acids in length) forms plaques in the brain leading to neurofibrillary tangles and ultimately neurodegeneration. Current research suggests longer forms of Aβ (>43 amino acids in length), which we dub “dark amyloid” are t he forms of Aβ responsible for AD pathology, and GSMs can alter the production of Aβ s of various lengths. The bottom left corner (Figure 2) is the structure of the parent GSM compound we used in this study. Figure 3 shows the derived analogs of the parent GSM that were tested. Sanjay Bhattarai is the medicinal chemist that derived these compounds. There were four cell lines these compounds were tested in: human embryonic kidney (HEK) cells with a familial AD mutation known as the Swedish mutation (notated as NL), human neuroblastoma cells (SH-SY5Y) with the Swedish mutation and an arctic mutation (notated as G) with various phenylalanine mutations (notated as F) designed to alter gamma-secretase generation of Aβ s. Confluent cells were treated with increasing compound concentrations at 1% final DSMO concentration or DSMO control. The media was collected twenty-four hours after treatment, and an ELISA was preformed to quantify the lengths of the present Aß protein as well as the IC50s of the compounds. Lei Liu, Chad Pope, and I handled the cell culture, GSM treatments, and worked to generate and collect the ELISA data. This project was one step in identifying the structure-activity relationship of the GSM compounds. The graphs correlate with the structures shown in Figure 3. We were searching for a GSM that stimulated overall increased trimming of Aβ , as indicated by increases in smaller Aβ s. An ideal GSM candidate would also preferentially lead to trimming of longer Aβ s, which we believe may be pathogenic in AD. SB-302, SB-303, and SB-305 all stimulate trimming of Aβ to more soluble forms, however, SB-303 was the most promising molecule, because it appears to also preferentially trim longer Aβ s as indicated by there being no change in the amounts of Aβ 40 and Aβ 42. The trimming of these dark amyloid
peptides hold potential to be therapeutic for AD progression and aid in testing the importance of dark amyloid in the progression of AD. SB-303 will be a used as a candidate future derived GSM analogs.
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