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Investigating the Functional Role of Drp1 in Mitochondrial Fission

Francy, Christopher Alfred
http://rave.ohiolink.edu/etdc/view?acc_num=case1480952643685349

Abstract Details

2017, Doctor of Philosophy, Case Western Reserve University, Pharmacology.
Mitochondria are dynamic organelles that continually undergo cycles of fission and fusion. Maintaining this fission/fusion balance is extremely important in sustaining cellular health. Mitochondrial fission serves to separate daughter mitochondria during division, segregate damaged mitochondria for autophagy and initiate apoptosis during disease conditions. In fact, in neurodegenerative, heart and liver disease, increased mitochondrial fission is observed, leading to cell death. The main mediator of mitochondrial fission is Drp1, a large GTPase of the dynamin superfamily. Drp1 can form oligomers capable of remodeling mitochondrial membranes, and this can lead to membrane partitioning. However, the mechanism of this process is not well understood. This work aimed to investigate the role of Drp1 in membrane constriction, the function of the uncharacterized variable domain (VD) of Drp1 and the structure of Drp1 on lipid membranes mimicking mitochondrial interactions. We assembled Drp1 on negatively charged membranes and induced constriction upon the addition of GTP. Moreover, we found that only GTP hydrolysis induces full constriction of the Drp1 lipid oligomer. Furthermore, the unstructured VD was found to keep Drp1 in a more active cytosolic conformation, as VD removal induced a hyperoligomeric state. We also found that alternatively spliced sequence insertion in the VD similarly reduces enzyme activity and narrows the diameters of Drp1-lipid polymers. In order to further investigate the function of these oligomers, we solved the 3D structure of Drp1 complexed on distinct lipid templates. Interestingly, we discovered that the mitochondrial specific lipid cardiolipin directly interacts with the VD and induces an activating conformational change to the rest of the Drp1 molecule. The helical assembly of Drp1 on CL templates is mediated exclusively through stalk and GTPase domain interaction sites. The VD has previously been termed a domain of unknown function, however our work characterizes the VD as a critical regulator of Drp1 self-assembly. We also find that the VD conformation influences stalk and novel G-domain orientations, which directly influence Drp1 enzymatic activity. This work advances our understanding of the Drp1 domains involved in the assembly and constriction of lipid bilayers. Overall, these findings will help us better understand Drp1 mediated mitochondrial fission.
Jason Mears (Advisor)
183 p.
Biochemistry; Pharmacology
mitochondria; Drp1; dynamin; structural biology; cryo-EM; GTPase

Recommended Citations

Citations

  • Francy, C. A. (2017). Investigating the Functional Role of Drp1 in Mitochondrial Fission [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1480952643685349

    APA Style (7th edition)

  • Francy, Christopher. Investigating the Functional Role of Drp1 in Mitochondrial Fission . 2017. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1480952643685349.

    MLA Style (8th edition)

  • Francy, Christopher. "Investigating the Functional Role of Drp1 in Mitochondrial Fission ." Doctoral dissertation, Case Western Reserve University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=case1480952643685349

    Chicago Manual of Style (17th edition)

case1480952643685349
872
© 2017, all rights reserved.
This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.