Degree Type

Thesis

Date of Award

2019

Degree Name

Master of Science

Department

Biochemistry, Biophysics and Molecular Biology

Major

Molecular, Cellular and Developmental Biology

First Advisor

Gustavo C. MacIntosh

Abstract

Lysosome Associated Membrane Proteins (LAMPs) are the most abundant proteins in the lysosomal membrane and are important for maintaining the structural integrity of the lysosomes and separating the hydrolytic enzymes inside the lysosomal lumen from the cell cytoplasm. Additional functions of Lamp proteins are continued to be discovered and they have been recently characterized for their involvement in autophagy in different mammalian systems. LAMP-1 and LAMP-2 are ubiquitously expressed in mammals. LAMP-2 has 3 splice variants and mutations in LAMP-2B have been shown to cause Danon disease in humans, characterized by the accumulation of autophagic vacuoles in the heart and skeletal muscle. In mice, the knockdown of both LAMP-1 and LAMP-2 leads to embryonic lethality with similar accumulation of autophagic vacuoles in their heart and skeletal muscle tissues. In Drosophila melanogaster, there is only 1 ortholog of LAMP proteins, Lamp-1, that has been solely used as a lysosomal marker with its basic function remaining unknown. We hypothesize that Drosophila can be a good model to study lysosomal defects and Danon disease. Our lab had previously characterized a loss of function (LOF) mutant for Lamp-1 and unlike the deletion of LAMP-1/LAMP-2 in vertebrate, the LOF flies are viable and fertile with no morphological abnormalities. However, the analysis of their cellular phenotype showed accumulation of Lysotracker- red (LTR) positive puncta suggesting an increase in the accumulation or decreased degradation of autophagic vacuoles (autophagosomes, lysosomes or autophagolysosomes) in fat body tissues. In preliminary evaluation of larval crawling ability of the both wild-type and mutant 3rd instar larvae, we found that the mutant larvae also present with decreased crawling ability. This behavioral phenotype together with the observed cellular phenotype suggest important functions for Lamp-1, but more research is needed to obtain a deeper understanding of the role of Lamp-1 in the lysosomes of Drosophila melanogaster.

Copyright Owner

Norin Yasin Chaudhry

Language

en

File Format

application/pdf

File Size

90 pages

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