Molecular dissection of the spindle assembly checkpoint signalling in Cryptococcus neoformans
dc.contributor.advisor
Hardwick, Kevin
dc.contributor.advisor
Bayne, Elizabeth
dc.contributor.author
Aktar, Koly
dc.contributor.sponsor
Darwin Trust of Edinburgh
en
dc.date.accessioned
2023-02-02T10:02:04Z
dc.date.available
2023-02-02T10:02:04Z
dc.date.issued
2023-02-02
dc.description.abstract
Cryptococcosis is a severe fungal infection caused by an opportunistic fungal
pathogen, Cryptococcus neoformans which has been medically significant for more
than half of the last century. This yeast displays noticeable ploidy shifts during in vivo
pulmonary infection. These polyploid cells often generate aneuploid progeny which
has been repeatedly reported as one of the main virulence factors for disease
progression. Given this capability of escaping equal chromosome segregation during
mitosis, they are possibly escaping several cell cycle controls including the spindle
assembly checkpoint. The spindle assembly checkpoint is undescribed in this fungal
pathogen. Therefore, I aimed to understand how this checkpoint signalling contribute
to cell division in C. neoformans. My current aim is to study one of the critical spindle
assembly checkpoint proteins, Mad1, which remains undescribed in this fungal
pathogen. Deletion of mad1 and mad2 in Cryptococcus showed sensitivity to anti-microtubules drugs. Microscopy and microfluidics data revealed that the mad1 and
mad2 mutants were unable to maintain mitotic arrest in response to such drugs. Both
proteins were also found to be important for Titan cell viability. Mad1 showed
localisation to unattached kinetochores of arrested cells. Purified Mad1 complexes
showed interactions with other checkpoint proteins Bub1, Mad2, Cdc20 and Mps1, by
co-immunoprecipitation and mass spectrometry. I believe that several of these
interactions are driven by phosphorylation. I found Mad1 to be phosphorylated by
recombinant Mps1 kinase. I have generated several Mad1 phospho-mutants and
some show defects in checkpoint signalling. Thus, Mad1 protein-protein interactions
could be regulated by kinases such as Mps1, Cdk, Plk1 or Bub1 kinase and this may
affect Mad1 interaction with Cdc20 (the APC/C co-activator). This study leads to a
plausible molecular explanation of Mad1 contribution in MCC assembly (Mitotic
checkpoint complex). The precise in vivo functions of Mad1 and more details of the
underlying molecular mechanisms of spindle assembly checkpoint signalling in this
understudied pathogenic fungus will be discussed.
en
dc.identifier.uri
https://hdl.handle.net/1842/39794
dc.identifier.uri
http://dx.doi.org/10.7488/era/3042
dc.language.iso
en
en
dc.publisher
The University of Edinburgh
en
dc.subject
Cryptococcus neoformans
en
dc.subject
aneuploidy
en
dc.subject
cell division control
en
dc.subject
cell cycle checkpoints
en
dc.subject
Mad1
en
dc.subject
Mad2
en
dc.subject
Titan cell viability
en
dc.title
Molecular dissection of the spindle assembly checkpoint signalling in Cryptococcus neoformans
en
dc.title.alternative
A molecular Dissection of the Spindle Assembly Checkpoint Signalling in Cryptococcus neoformans
en
dc.type
Thesis or Dissertation
en
dc.type.qualificationlevel
Doctoral
en
dc.type.qualificationname
PhD Doctor of Philosophy
en
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