Coblentz, Jessica
(2015)
LOSS OF TRPML1 ALTERS CELLULAR FUNCTIONS OUTSIDE OF THE LYSOSOME: DISSECTING THE RELATIONSHIP BETWEEN LYSOSOMAL AND MITOCHONDRIAL HEALTH IN MLIV.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
The transient receptor potential mucolipin 1 (TRPML1) is a lysosomal ion channel permeable to cations, including Fe2+. Mutations in MCOLN1, the gene coding for TRPML1, cause the lysosomal storage disease (LSD) Mucolipidosis type IV (MLIV). Recent evidence from our lab suggests that the lysosome functions as a cytoprotective organelle that works to sequester cytotoxic material to prevent cellular damage to other organelles. However, the role of TRPML1 in the cell is disputed and the mechanisms of cell deterioration in MLIV are unclear. The recent demonstration of Fe2+ buildup in MLIV cells raised the possibility that TRPML1 dissipates lysosomal Fe2+ and prevents its accumulation. In order to determine the function of TRPML1 and identify the molecular mechanisms leading to MLIV pathogenesis, I have analyzed the involvement of TRPML1 in the cytoprotective function of the lysosome. Since Fe2+ catalyzes the production of reactive oxygen species (ROS), I set out to test whether or not the loss of TRPML1 promotes ROS production by Fe2+ trapped in lysosomes. My data shows that TRPML1-deficient retinal-pigmented epithelial (RPE1) cells develop elevated levels of oxidative stress that promote lipid peroxidation, activation of mitochondrial fission factors, mitochondrial fragmentation, mitochondrial depolarization, and decreased mitochondrial metabolism. These deleterious effects of TRPML1 deficiency were aggravated by Fe2+ exposure, but were reversed by incubation with the antioxidant α-tocopherol. As this data suggests, TRPML1 redistributes Fe2+ between the lysosomes and the cytoplasm. This work has led to a better understanding of TRPML1’s role in cellular cytoprotection and in lysosomal transition metal homeostasis with regards to Fe2+. As the oxidative burden in TRPML1-deficient RPE1 cell has been recapitulated in MLIV patient fibroblasts and the MLIV mouse model, this data has also provided new developments into the molecular mechanisms of MLIV pathogenesis. Beyond suggesting a new model for MLIV pathogenesis and identifying novel therapeutic treatments for MLIV, this data shows that TRPML1’s role in the cell extends outside of lysosomes.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
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| ETD Committee: |
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| Date: |
12 January 2015 |
| Date Type: |
Publication |
| Defense Date: |
14 October 2014 |
| Approval Date: |
12 January 2015 |
| Submission Date: |
5 December 2014 |
| Access Restriction: |
2 year -- Restrict access to University of Pittsburgh for a period of 2 years. |
| Number of Pages: |
158 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Dietrich School of Arts and Sciences > Biological Sciences |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
Lysosome, Mitochondria, Iron, TRPML1, Mucolipin-1, Mucolipidosis Type IV, GDAP1, Reactive Oxygen Species, HMOX1 |
| Date Deposited: |
12 Jan 2015 15:33 |
| Last Modified: |
12 Jan 2017 06:15 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/23668 |
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