The Role of p66Shc in Stem Cells: Signalling, Identity and Apoptosis

Adaptor proteins of the Shc family link receptor tyrosine kinases (RTKs) to downstream signalling, thereby shaping cell fate decisions. While the canonical isoforms p52Shc and p46Shc act as Ras–MAPK transducers, the longer p66Shc isoform harbours an additional CH2 domain that confers distinct regulatory properties. Despite long-standing associations with oxidative stress and apoptosis, the physiological roles of p66Shc in stem cells remain poorly defined. This thesis examines the role of p66Shc in signalling, apoptosis, and extracellular matrix (ECM)-dependent behaviour in embryonic stem cells (ESCs) and neural stem cells (NSCs). In ESCs, deletion of p66Shc enhanced ERK phosphorylation and STAT3 serine-727 phosphorylation, thereby sustaining naïve pluripotency even in the absence of chemical MEK/GSK3β inhibition. These effects are consistent with a model in which p66Shc acts as a competitive inhibitor of Grb2 recruitment, restraining ERK–STAT3 signalling to promote lineage priming. In NSCs, p66Shc loss conferred resistance to apoptosis induced by epidermal growth factor (EGF) withdrawal, EGF-receptor inhibition, or MEK inhibition, but not to classical mitochondrial oxidants. These results support an “ERK-gated” framework, in which p66Shc couples the collapse of ERK signalling to intrinsic apoptotic execution. Finally, ECM-specific assays revealed that p66Shc deletion impaired adhesion, proliferation, and migration on gelatin, but not on laminin. Laminin fully rescued MAPK phosphorylation and motility defects, indicating that p66Shc specifically supports integrin-mediated ERK–cytoskeletal signalling. Together, these findings establish p66Shc as a context-dependent regulator of stem cell fate: antagonistic in RTK-driven signalling, pro-apoptotic during growth factor deprivation, and permissive in integrin–mediated adhesion and migration. This duality reconciles the contradictory literature and highlights p66Shc as a developmental quality control checkpoint. Beyond stem cell biology, the work has implications for understanding apoptosis resistance, ECM interactions, and therapeutic responses to EGFR–MEK inhibition.

Name thesis:degree_name

Ph D

Discipline thesis:degree_discipline

Biology

Grantor dc:publisher

The University of Western Ontario

Year dc:date.issued

2025

Author dc:creator

• Powell, Andrew

Advisors dc:contributor.advisor

• Betts, Dean
• Cumming, Robert

• p66Shc
• SHC1
• adaptor proteins
• signalling
• RTK
• EGF
• LIF
• ERK
• STAT3
• apoptosis
• pluripotency
• embryonic stem cells
• neural stem cells
• extracellular matrix
• integrins

Statement dc:rights

• Attribution 4.0 International

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/20.500.14721/39251

OAI identifier oai:identifier

oai:uwo.scholaris.ca:20.500.14721/39251