Type
Text
Type
Dissertation
Advisor
Frohman, Michael A. | Daniel F. Bogenhagen | Robert S. Haltiwanger | Deborah A. Brown.
Date
2010-08-01
Keywords
diacylglycerol, Lipin 1, mitochondrial dynamics, mitochondrial fusion assay, MitoPLD, phosphatidic acid | Biology, Cell -- Biology, Molecular
Department
Department of Molecular and Cellular Pharmacology
Language
en_US
Source
This work is sponsored by the Stony Brook University Graduate School in compliance with the requirements for completion of degree.
Identifier
http://hdl.handle.net/11401/72542
Publisher
The Graduate School, Stony Brook University: Stony Brook, NY.
Format
application/pdf
Abstract
Mitochondria continuously undergo fusion and fission, the relative rates of which define their morphology. Mitochondrial fusion is currently assayed by fusing together cells expressing GFP or RFP in their mitochondria and then scoring the frequency of cells with yellow mitochondria (representing fused green and red mitochondria). However, this assay is labor intensive and only semi-quantitative. I developed a reporter system consisting of split fragments of Renilla luciferase and YFP fused to mitochondrial matrix-targeting sequences and to leucine zippers to trigger dimerization. The assay enables fusion to be quantitated both visually for individual cells and on a population level using chemiluminescence, laying the foundation for high throughput small molecule and RNAi screens for modulators of mitochondrial fusion. I used the assay to examine cytoskeletal roles in fusion progression. The mammalian Phospholipase D superfamily member MitoPLD localizes to mitochondria and facilitates fusion by generating the signaling lipid phosphatidic acid (PA). Independently, the Drosophila homolog of MitoPLD, Zucchini (Zuc), was proposed to be a cytoplasmic nuclease and shown to be required for piRNA generation, a critical step in oogenesis. I show here that Zuc localizes to mitochondria. Conversely, mice lacking MitoPLD exhibit the germ cell degeneration observed in mice lacking other piRNA components. These findings identify the first mitochondrial protein required for piRNA generation. MitoPLD generates PA on the mitochondrial surface. The PA then recruits another signaling enzyme, the PA phosphatase Lipin 1, to convert the PA to diacylglycerol and promote fission, suggesting a new mechanism for mitochondrial morphology homeostasis. MitoPLD-/- fibroblasts exhibit shortened mitochondria and spermatocytes lack intermitochondrial cement (nuage), a structure that is implicated in piRNA generation. I propose that mitochondrial-surface PA generated by MitoPLD/Zuc recruits nuage components critical for piRNA production.
Recommended Citation
Huang, Huiyan, "Development of a quantitative assay for mitochondrial fusion and characterization of a lipid signaling pathway on the mitochondrial surface" (2010). Stony Brook Theses and Dissertations Collection, 2006-2020 (closed to submissions). 1746.
https://commons.library.stonybrook.edu/stony-brook-theses-and-dissertations-collection/1746