Imaging Lysosomes and Secreted Cathepsins

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Mohebbi, Nina
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Cathepsins, members of the papain family of proteases, have been implicated in the initiation and progression of tumors, cardiovascular disease, and osteoporosis. Due to their involvement in multiple diseases, many studies focus on cathepsins in these disease progressions. Cathepsin inhibitors have also been suggested as treatments for their associated diseases. Unfortunately, due to severe side effects, many inhibitors were terminated at the Phase II clinical testing stage. This suggests not enough is known about the cellular mechanism associated with cathepsins to ensure successful translation of these inhibitors to clinical applications. Due to their localization within lysosomes, we hypothesize that lysosomal activity, movement, and secretion will be tied to levels of cathepsin activity. Fluorescence microscopy with custom image analysis is used to track lysosomes within the cell and biochemical assays are used to assess enzymatic activity. These results are used to evaluate potential correlations between lysosome characteristics, such as size and/or cathepsin localization and the level of cathepsin activity. Results from an immunofluorescence experiment showed cathepsin L present inside of the cell is not exclusive to storage within lysosomes. Results from image analysis also show an increase in lysosome size when cathepsins inhibitor E-64 is added to cells. This could be a result of cargo in lysosomes not being broken down. The long-term implications of this research include providing clinicians and pharmaceutical developers with ways to predict the rate of disease progression on a patient-to-patient basis, and therefore more personally evaluate risk and designate aggressive or more passive treatment options.
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Undergraduate Thesis
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