The Ras-MAPK axis is a core signal-transduction system that converts extracellular cues into transcriptional, metabolic, and structural responses in neurons and glia.[1][2] In the central nervous system, this pathway helps determine whether cells mount adaptive plasticity programs or transition into sustained stress signaling states associated with neurodegeneration.[3][4]
Mechanistically, Ras proteins act as molecular switches upstream of the RAF-MEK-ERK cascade. In neurodegenerative disorders, pathway behavior is shaped by signal duration, cell type, and pathway cross-talk, especially with PI3K-AKT-mTOR signaling, inflammatory kinase programs, and mitochondrial quality-control modules.[4:1][5]
Neurotrophin receptors, growth-factor receptors, and selected GPCR-associated modules recruit adaptor complexes that activate Ras-family GTPases by promoting GDP-to-GTP exchange.[1:1][2:1] This activation step is the principal kinetic gate that determines downstream pathway intensity and duration.
GTP-bound Ras recruits RAF kinases, enabling MEK1/2 phosphorylation and subsequent ERK1/2 activation.[1:2][3:1] Activated ERK regulates cytoskeletal proteins, local translation, and transcription-factor programs relevant to neuronal survival, plasticity, and inflammatory responses.[2:2][3:2]
Transient signaling supports physiologic synaptic adaptation, while prolonged activation can drive maladaptive outputs including inflammatory amplification, abnormal protein phosphorylation, and neuronal dysfunction.[3:3][5:1]
Ras-MAPK is best viewed as a hub rather than an isolated linear pathway. Important integration points include:
In Alzheimer's disease, MAPK pathway dysregulation is linked to amyloid stress, inflammatory signaling, and tau-related toxicity.[5:3][9][10] Experimental data indicate that altered ERK/p38 dynamics can worsen pathology, while selective modulation of inflammatory MAPK signaling can improve outcomes in APP-transgenic systems.[10:1]
Key mechanistic themes:
This supports a working model where Ras-MAPK acts as a disease-amplifying network component that interacts with amyloid, tau, and neuroinflammatory modules rather than serving as a single initiating lesion.[5:4][7:2]
In Parkinson's disease, ERK pathway behavior is similarly bidirectional: physiologic signaling can support dopaminergic adaptation, while sustained activation under toxin/proteostasis stress associates with degeneration phenotypes.[6:1][12]
Mechanistic evidence includes:
Recent reviews frame AKT/ERK co-regulation as a key systems-level axis in PD, emphasizing pathway coupling instead of single-branch intervention.[14]
ALS literature supports MAPK dysregulation as part of a mixed neuronal-glial stress network that includes inflammatory and RNA/proteostasis pathology.[15][16]
Important points:
Translationally, ALS remains a setting where pathway modulation will likely require cell-state stratification to avoid suppressing compensatory signaling in surviving motor circuits.[15:2][17:1]
Ras-MAPK signaling is central to memory-linked and activity-dependent plasticity programs.[2:3][3:4] This creates a core therapeutic tension in neurodegeneration:
Precision control of signal amplitude and timing, rather than blanket suppression, is therefore the most defensible strategy for CNS applications.[3:5][4:3]
Vithayathil J, Pucilowska J, Landreth GE. RAS and downstream RAF-MEK and PI3K-AKT signaling in neuronal development, function and dysfunction. Biological Chemistry. 2016. ↩︎ ↩︎ ↩︎
Sweatt JD. 'The neuronal MAP kinase cascade: a biochemical signal integration system subserving synaptic plasticity and memory'. Journal of Neurochemistry. 2001. ↩︎ ↩︎ ↩︎ ↩︎ ↩︎
Thomas GM, Huganir RL. MAPK cascade signalling and synaptic plasticity. Nature Reviews Neuroscience. 2004. ↩︎ ↩︎ ↩︎ ↩︎ ↩︎ ↩︎ ↩︎
Jalili-Baleh L, et al. The Role of PI3K/Akt and ERK in Neurodegenerative Disorders. Neurotoxicity Research. 2019. ↩︎ ↩︎ ↩︎ ↩︎ ↩︎
Kim EK, Choi EJ. Pathological roles of MAPK signaling pathways in human diseases. Biochimica et Biophysica Acta. 2010. ↩︎ ↩︎ ↩︎ ↩︎ ↩︎
Kulich SM, Chu CT. 'Sustained extracellular signal-regulated kinase activation by 6-hydroxydopamine: implications for Parkinson''s disease'. Journal of Neurochemistry. 2001. ↩︎ ↩︎ ↩︎
Jiang C, Shi J, Li M, et al. 'Neuroinflammation in Alzheimer''s Disease: Current Progress in Molecular Signaling and Therapeutics'. Inflammation. 2023. ↩︎ ↩︎ ↩︎ ↩︎
Kim JH, et al. Involvement of p38 MAPK in Synaptic Function and Dysfunction. International Journal of Molecular Sciences. 2020. ↩︎
Amadoro G, et al. NMDA receptor mediates tau-induced neurotoxicity by calpain and ERK/MAPK activation. Proceedings of the National Academy of Sciences of the United States of America. 2006. ↩︎ ↩︎
Kracht L, et al. p38α-MAPK-deficient myeloid cells ameliorate symptoms and pathology of APP-transgenic Alzheimer's disease mice. Aging Cell. 2022. ↩︎ ↩︎ ↩︎
Li K, et al. CD2AP deficiency aggravates Alzheimer's disease phenotypes and pathology through p38 MAPK activation. Translational Neurodegeneration. 2024. ↩︎
Choi WS, et al. MPP+ increases alpha-synuclein expression and ERK/MAP-kinase phosphorylation in human neuroblastoma SH-SY5Y cells. Brain Research. 2002. ↩︎ ↩︎
Bonello F, Hassoun SM, Mouton-Liger F, et al. Aberrant mitochondrial morphology and function associated with impaired mitophagy and DNM1L-MAPK/ERK signaling are found in aged mutant Parkinsonian LRRK2. Autophagy. 2021. ↩︎
Gurung M, et al. Unraveling the AKT/ERK cascade and its role in Parkinson disease. Archives of Toxicology. 2024. ↩︎
Mejzini R, et al. Mitogen-Activated Protein Kinase Pathway in Amyotrophic Lateral Sclerosis. Biomedicines. 2021. ↩︎ ↩︎ ↩︎
Tortarolo M, et al. 'Inter- and intracellular signaling in amyotrophic lateral sclerosis: role of p38 mitogen-activated protein kinase'. Neuro-Degenerative Diseases. 2006. ↩︎ ↩︎
Wang M, et al. MAPK/MAK/MRK overlapping kinase (MOK) controls microglial inflammatory/type-I IFN responses via Brd4 and is involved in ALS. Proceedings of the National Academy of Sciences of the United States of America. 2023. ↩︎ ↩︎