Molecular and cellular roles of the N-end rule pathway in apoptotic cell death in mammalian-derived cell lines

• Author / Creator

  Eldeeb,Mohamed AM

• Cellular stresses and signaling that lead to the initiation of apoptotic pathways often result in the activation of proteases such as caspases which in turn culminate in the generation of proteolytically activated protein fragments with new or altered roles. Recent work has revealed that the activity of some of the caspase-generated activated pro-apoptotic protein fragments can be mitigated via their selective degradation by the N-end rule pathway. In this work, I report the investigations that examined the role of the N-end rule pathway in regulating apoptotic cell death via selective protein degradation of specific crucial cleaved pro- and anti-apoptotic fragments in mammalian cell lines. My investigation has focused on three cleaved protein fragments (cleaved fragments of Lyn kinase, BMX kinase and PKC-theta). Selective degradation of the C-terminal fragments of these three diverse protein kinases implicates an expansive role for the N-end rule pathway in the complex network of apoptotic pathways. The degradation of the anti-apoptotic cleaved Lyn kinase by the N-end rule pathway in K562 cell line revealed that N-end rule pathway may target anti-apoptotic protein fragments and thus regulates the apoptotic threshold in certain cells. Tellingly, the N-end-rule-mediated degradation of the pro-apoptotic cleaved BMX kinase in cancer-derived cell lines provides an example for an N-end rule-mediated anti-apoptotic response for cancer cell survival via destroying an endogenous caspase-generated pro-apoptotic protein fragment. Lastly, I have determined that the pro-apoptotic cleaved fragment of PKC-theta is unstable in mammalian cells as its N-terminal lysine targets it for proteasomal degradation via the N-end rule pathway and this degradation dampens the potent pro-apoptotic function of the cleaved fragment of PKC-theta. Collectively, this work delineates some of the functional scope of N-end rule pathway with respect to apoptotic cell death and supports the notion that targeting N-end rule machinery may have therapeutic implications.

• Subjects / Keywords

  • Protein degradation
  • Cell death
  • N-end rule pathway

• Graduation date

  Fall 2017

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R39W09F5K

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. 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.