Notch signaling is a highly conserved pathway that plays critical roles in neural development, adult neurogenesis, and cellular differentiation. In corticobasal syndrome (CBS) and progressive supranuclear palsy (PSP), both classified as 4-repeat (4R) tauopathies, dysregulation of Notch signaling contributes to neuronal vulnerability and impaired repair mechanisms. This section examines Notch pathway alterations in CBS/PSP and their relationship to tau pathology. [1]
CBS and PSP share common pathological features of 4R tau accumulation, but exhibit distinct clinical presentations 1. While CBS presents with asymmetric cortical dysfunction and basal ganglia degeneration leading to apraxia, alien limb phenomena, and cortical sensory loss, PSP is characterized by vertical gaze palsy, postural instability, and axial rigidity with progressive gait disturbance. Notch signaling interacts with tau pathology through multiple mechanisms, including regulation of tau phosphorylation, modulation of neurogenesis, and control of glial cell function. Understanding these interactions may reveal novel therapeutic targets for disease modification. [2]
The Notch pathway's role in neurodegeneration extends beyond its developmental functions. In the adult brain, Notch signaling regulates neural stem cell populations, modulates synaptic plasticity, and influences glial cell function. Dysregulation of these processes contributes to the progressive neurodegeneration observed in both CBS and PSP. [3]
The Notch family includes multiple receptors and ligands with distinct expression patterns 2: [4]
Notch Receptors: [5]
Notch Ligands (DSL family): [6]
The ligands are transmembrane proteins requiring cell-cell contact for Notch activation. This contact-dependent signaling allows precise spatial regulation of Notch activity in the brain. [7]
The Notch pathway involves sequential proteolytic cleavage: [8]
Canonical pathway steps: [9]
Downstream targets: Hes (Hairy and Enhancer of Split) and Hey (Hairy/Enhancer-of-Split related with YRPW motif) transcription factors regulate genes involved in differentiation, proliferation, and survival [10]
Notch signaling plays essential roles in adult neurogenesis 3:
The balance between Notch activation and inhibition determines whether neural stem cells remain proliferative or differentiate into neurons. This balance is critical for ongoing neurogenesis in the adult brain.
Notch contributes to synaptic plasticity through multiple mechanisms 4:
Notch receptors are present at both excitatory and inhibitory synapses, where they modulate synaptic strength and plasticity through interactions with postsynaptic density proteins.
Notch signaling regulates glial cell types:
Studies suggest Notch pathway alterations in tauopathies 5:
The motor cortex and basal ganglia, regions prominently affected in CBS, show particular Notch pathway alterations. Immunohistochemical studies demonstrate changes in Notch immunoreactivity in neurons with tau inclusions.
Notch signaling interacts with tau pathology in complex ways 6:
The relationship between Notch signaling and tau creates a vicious cycle: tau pathology impairs Notch signaling, which reduces neuroprotection and neurogenesis, leading to further tau accumulation and spread.
The pattern of Notch dysregulation in CBS/PSP follows the regional distribution of tau pathology:
Therapeutic strategies targeting Notch signaling include 7:
Challenges in Notch-targeted therapy 8:
Promising approaches include:
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Litvan I, et al. Clinical features and management of corticobasal syndrome. Lancet Neurology. 2020. ↩︎
Boxer AL, et al. Comparison of PSP and CBS phenotypes. Neurology. 2020. ↩︎
Kovacs GG, et al. Staging of tau pathology in PSP. Acta Neuropathologica. 2022. ↩︎
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Chahine LM, et al. Biomarkers for tauopathies in CBS/PSP. Neurobiology of Aging. 2020. ↩︎
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McKinnon PJ. DNA repair and the cell cycle as targets in tauopathies. Experimental Neurology. 2020. ↩︎