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Inheritance of peroxisomes in the yeast Yarrowia lipolytica Open Access
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- Type of item
- Degree grantor
University of Alberta
- Author or creator
- Supervisor and department
Rachubinski, Richard (Cell Biology)
- Examining committee member and department
Wang, Zhixiang (Cell Biology)
Mullen, Robert (University of Guelph)
Casey, Joseph (Physiology)
Eitzen, Gary (Cell Biology)
Department of Cell Biology
- Date accepted
- Graduation date
Doctor of Philosophy
- Degree level
Peroxisomes are indispensable organelles that perform many essential metabolic activities. Thus, eukaryotic cells have evolved molecular mechanisms to ensure the inheritance of peroxisomes from mother cell to daughter cell at cell division. In the budding yeast Saccharomyces cerevisiae, the class V myosin motor, Myo2p, interacts with its peroxisomal receptor, Inp2p, to move peroxisomes along actin from mother cell to bud, while the peroxisomal membrane protein Inp1p functions to tether peroxisomes to the cell cortex.
In this thesis, I report the results of investigations of peroxisome inheritance using the dimorphic yeast Yarrowia lipolytica as a model system.
We showed that peroxisome mobility and inheritance are dependent on actin in Y. lipolytica. Interrogation of the Y. lipolytica genome revealed one class V myosin. This myosin V is involved in transporting peroxisomes from mother cell to bud. We characterized YlInp1p, the othologue of S. cerevisiae Inp1p, as the first peroxisomal protein required for peroxisome inheritance in Y. lipolytica. We demonstrated that YlInp1p functions to anchor peroxisomes in both mother cell and bud. YlInp1p has an additional role in the dimorphic transition from the yeast form to the hyphal form in Y. lipolytica.
We identified Pex3Bp, a paralogue of Pex3p, as the peroxisome-specific receptor for myosin V in Y. lipolytica. Pex3Bp interacts directly with the globular tail of myosin V. Pex3Bp also interacts with itself and with Pex3p. In cells lacking Pex3Bp, peroxisomes are preferentially retained in the mother cell, while the majority of peroxisomes gather and are transferred to the bud in cells overproducing Pex3Bp. Overexpression of PEX3 can partially complement the phenotype of pex3B∆ cells, while overexpression of PEX3B cannot complement the phenotype of pex3∆ cells. Interestingly, Pex3p, which has been shown previously to function in the de novo formation of peroxisomes from the ER, also interacts directly with the globular tail of myosin V. Therefore, Pex3p is involved in peroxisome inheritance. In addition, cells lacking Pex3Bp contain hyperelongated, tubulo-reticular peroxisomes, indicating that Pex3Bp has a role in peroxisome morphology. Our findings suggest that both Pex3Bp and Pex3p are multifunctional proteins that are involved in different steps of the peroxisome biogenic cascade.
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