Date of Award
Master of Science
Microbiology and Immunology
Dr. Sung Kim
Autophagy is a vesicular system which is a lysosomal degradation pathway found in organisms ranging from yeast to mammals. To date, extensive studies have unraveled the mechanism of autophagy biogenesis and more than thirty autophagy related (ATG) genes have been identified. However, detailed molecular mechanisms of autophagic process have not yet been elucidated. This study uncovered a novel role of cathepsin B (CTSB), a lysosomal protease, in autolysosome clearance, termed autolysosome efflux. CTSB-deficient immortalized and primary macrophages showed higher accumulations of autophagy specific protein microtubule-associated protein 1 light chain 3(LC3)-II and they showed greater numbers of FITC-LC3 punta within the cells. These LC3 punta colocalized with dequenched (DQ)-fluorescent-conjugatedBSA, a lysosomal fluorescent marker, which indicated that the accumulating autophagy vesicles in CTSB-deficient cells were autolysosomes. Further investigations showed that CTSB-deficient macrophages accumulated autolyososomes due to defects in autolysosome efflux. These results suggested that CTSB is a key player in mediating autolysosome efflux. A clear linkage between autolysosome efflux and cell death was not found. This study implicates that CTSB may be used as a potential tool to further investigate autolysosome vesicle trafficking and identify the role of autolysosome efflux. Further research in autolysosome efflux will provide insights into the autophagy life cycle and possibly provide novel therapeutic strategies for treating many diseases caused by defective or overactive autophagy such as neurodegenerative diseases, pancreatitis or cancer.
Ham, Boram, "Cathepsin B-mediated autolysosome efflux and cell death" (2010). Digitized Theses. 3685.