Protein trafficking and autophagy in the moulting cycle of C. elegans

Batas, Anastasios (2018) Protein trafficking and autophagy in the moulting cycle of C. elegans. PhD thesis, University of Glasgow.

Abstract

Endosomal trafficking and autophagy are two fundamental processes of eukaryotic cell biology, from unicellular organisms such as yeast to multicellular metazoans such as C.elegans and Humans. Both processes are involved in a diverse number of physiological processes and implicated in a number of pathologies. A recent study has exhibited a mutation on the SM protein Vps45 as a cause of severe congenital neutropenia in humans. The same mutation in yeast causes defects in endosome to vacuole trafficking in S.cerevisiae as well as a temperature sensitive lethality at the non-permissive temperature. A null allele of vps-45 in C.elegans results in developmental arrest during the highly secretory phase of moulting in a similar temperature conditional manner to yeast and defects in yolk protein trafficking. The work presented in this thesis aims to provide basic understanding in an animal model of the impact of loss of Vps45 function that might be informative of the reason for the death of the highly secretory neutrophil cells under the absence of a functional Vps45 protein. The vps-45 and unc-51 mutants as well as a novel unc-51 vps-45 double mutant where possible, were characterised for lifespan, duration of post- embryonic development as well as moulting duration. Reduced embryonic viability, reduced lifespan as well as delays in the moulting process were identified. Data suggested that both autophagy and protein trafficking play a role in C.elegans development through unc-51 and vps-45 respectively.
In addition to this, the seam cells of both the vps-45 and unc-51 defective C.elegans were observed during the moult using an autophagy marker. An increase in autophagic activity during the moult was observed, which was more pronounced in the case of the vps-45 mutant. As such the obtained data suggest autophagy and endosomal trafficking play an important role in the moulting process.
Following up to previous work conducted in our lab in yeast defective for Vps45 trafficking which exhibited increased sensitivity to oxidative stress, the redox state of the vps-45 and unc-51 animals as well as their sensitivity to oxidative stress was assessed using a set of ER and cytosolic GFP markers and killing assays. Both the vps-45 and unc-51 mutants showed a higher sensitivity to oxidative stress, with the unc-51 exhibiting the more pronounced phenotype overall. These results came in agreement with the shorter lifespan phenotypes exhibited by both mutants in the previous experiments, possibly as a result of accumulation of ROS, as well as the severe defects of the double mutant.
Finally, a suppressor identified for the moulting death of the vps-45 mutant was characterized for a set of phenotypes, in order to exclude suppression of any of the other phenotypes identified for the vps-45 mutant. Furthermore, the suppressor was identified as being autosomal and recessive and as thus an SNP full genome sequencing technique was employed, which gave rise to two suppression loci in two different chromosomes, along with two different subpopulations corresponding to these loci which exhibited different growing patterns.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: C. elegans, moulting, protein trafficking, autophagy, vps-45, unc-51, atg-1, seam cells, snares, SM proteins, neutropenia.
• Subjects: Q Science > Q Science (General); Q Science > QH Natural history > QH301 Biology; Q Science > QH Natural history > QH426 Genetics
• Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Molecular Biosciences
• Supervisor's Name: Johnstone, Dr. Iain and Nia, Prof. Bryant
• Date of Award: 2018
• Depositing User: Mr Anastasios/A Batas
• Unique ID: glathesis:2018-8856
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 27 Feb 2018 11:36
• Last Modified: 12 Apr 2018 08:22
• URI: https://theses.gla.ac.uk/id/eprint/8856