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Evolution of the vesicle formation machinery Open Access


Other title
Membrane traffic
Organelle Paralogy Hypothesis
Protocoatomer Hypothesis
Type of item
Degree grantor
University of Alberta
Author or creator
Schlacht, Alexander Douglas William
Supervisor and department
Dacks, Joel
Examining committee member and department
LaPointe, Paul (Department of Cell Biology)
Gallin, Warren (Department of Biological Sciences)
Turkewitz, Aaron (Department of Molecular Genetics, University of Chicago)
Melancon, Paul (Department of Cell Biology)
Department of Cell Biology

Date accepted
Graduation date
Doctor of Philosophy
Degree level
One of the features that distinguishes eukaryotes from prokaryotes is the membrane trafficking system. This system underpins much of the functionality of the eukaryotic cell, and is necessary for feeding, motility and communication. Analyses aimed at addressing the evolution of this system have revealed tremendous complexity in the Last Eukaryotic Common Ancestor, pointing to an even earlier origin. However, the events giving rise to this system and its subsequent diversification are poorly understood. Comparative genomic and phylogenetic analyses aimed at addressing the evolution of the membrane trafficking system have focused largely on the machinery of vesicle fusion. Here, I examine the evolution of machinery involved in vesicle formation. Comparative genomic and phylogenetic analyses were used to assess the conservation and evolution of protein families involved in the regulation of vesicle coat formation. ArfGAPs and ArfGEFs are regulatory proteins for the small GTPase Arf, a key regulator of vesicle coat formation. I found that five of ten previously identified ArfGAP subfamilies were present in the LECA, and I identify a previously unreported ArfGAP subfamily that is absent from humans and yeast. I also report that the LECA possessed three of the six described ArfGEF subfamilies. COPII is a heteromeric coat complex necessary for the transport of cargo from the endoplasmic reticulum to the Golgi apparatus. I found that all seven components were present in the LECA, five of which are ubiquitously conserved across eukaryotes. The other two are frequently missing. TSET is a newly identified adaptin-like coat complex with a likely role in endocytosis. I found that this complex is broadly distributed, indicating its presence in the LECA. However, it has been frequently lost from multiple eukaryotic lineages, including that giving rise to humans and fungi. Analysis of these gene families revealed multiple patterns of protein conservation, including ubiquitous and lineage-specific patterns, but also components with a “patchy” distribution that had previously been under appreciated. That some of these are missing from traditional cell biological systems such as humans and yeast, suggests the need to consider other eukaryotes as model organisms in order to fully comprehend the diversity of eukaryotic cell biology. Analysis of these components also revealed some of the earliest events that may have occurred during the evolution of the trafficking system, in addition to convergent roles of multiple coat complexes in membrane trafficking.
This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for the purpose of private, scholarly or scientific research. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.
Citation for previous publication
Schlacht, A., Mowbrey, K., Elias, M., Kahn, R.A., Dacks, J.B. 2013. Ancient complexity, opisthokont plasticity, and discovery of the 11th subfamily of ArfGAP proteins. Traffic 14: 636-649Schlacht, A., Dacks, J.B. 2015. Unexpected ancient paralogues and an evolutionary model for the COPII coat complex. Genome Biology and Evolution 7: 1098-1109Hirst, J., Schlacht, A., Norcott, J.P., Traynor, D., Bloomfield, G., Antrobus, R., Kay, R.R., Dacks, J.B., Robinson, M.S. 2014. Characterization of TSET, an ancient and widespread membrane trafficking complex. eLife 3: e02866Schlacht, A., Herman, E.K., Klute, M.J., Field, M.C., Dacks, J.B. 2014. Missing pieces of an ancient puzzle: evolution of the eukaryotic membrane-trafficking system. In Cold Spring Harbor Perspectives: The Origin and Evolution of Eukaryotes (eds. Keeling, P.J., Koonin, E.V.) Cold Spring Harbor Press

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