AKT

Overview

AKT, also known as Protein Kinase B (PKB), is a serine/threonine protein kinase that functions as a critical signaling hub governing cell survival, growth, metabolism, and proliferation. First identified as a viral oncogene in the AKT8 murine retrovirus and subsequently recognized as a key mediator of phosphoinositide 3-kinase (PI3K) signaling, AKT has emerged as an essential regulator of neuronal homeostasis and neuroprotection. In mammals, AKT exists in three isoforms—AKT1 (PKBα), AKT2 (PKBβ), and AKT3 (PKBγ)—encoded by separate genes with distinct but overlapping tissue distributions. AKT1 is ubiquitously expressed, AKT2 shows enrichment in insulin-responsive tissues, and AKT3 is particularly abundant in the brain and nervous system, where it plays specialized roles in neuronal development and function. ^{1TGF-β1 mediates hypoxia-preconditioned olfactory mucosa mesenchymal stem cells improved neural functional recovery in Parkinson's disease models and patients.2024 · Mil Med Res · DOI 10.1186/s40779-024-00550-7 · PMID 39034405Open reference}

The importance of AKT in neurodegeneration stems from its position at the intersection of multiple protective signaling cascades. Neurotrophic factors such as brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) activate AKT through receptor tyrosine kinase signaling, and this pathway is essential for neuronal survival, synaptic plasticity, and cognitive function. Dysregulation of AKT signaling has been implicated in Alzheimer’s disease, Parkinson’s disease, amyotrophic lateral sclerosis (ALS), and Huntington’s disease, making it a molecule of considerable therapeutic interest. ^{2The Akt pathway in oncology therapy and beyond (Review).2018 · Int J Oncol · DOI 10.3892/ijo.2018.4597 · PMID 30334567Open reference}

Function/Biology

AKT activation is initiated at the plasma membrane through a well-characterized phosphoinositide-dependent mechanism. Upon activation of receptor tyrosine kinases or G-protein-coupled receptors, PI3K phosphorylates phosphatidylinositol (4,5)-bisphosphate (PIP2) to generate phosphatidylinositol (3,4,5)-trisphosphate (PIP3). AKT binds to PIP3 through its pleckstrin homology (PH) domain, bringing it to the membrane where it undergoes conformational changes enabling phosphorylation at two critical sites. PDK1 (3-phosphoinositide-dependent kinase 1) phosphorylates AKT at threonine 308 (Thr308) in the activation loop, while mTORC2 (mechanistic target of rapamycin complex 2) phosphorylates serine 473 (Ser473) in the hydrophobic motif, resulting in full enzymatic activation. ^{3Gastrodin promotes CNS myelinogenesis and alleviates demyelinating injury by activating the PI3K/AKT/mTOR signaling.2025 · Acta Pharmacol Sin · DOI 10.1038/s41401-025-01492-z · PMID 40011630Open reference}

Once activated, AKT phosphorylates over 100 downstream substrates, modulating diverse cellular processes. Key targets include glycogen synthase kinase 3 beta (GSK3β), which AKT phosphorylates at Ser9 to inhibit its activity, thereby preventing tau hyperphosphorylation and protecting cytoskeletal integrity. AKT also activates mTORC1 through phosphorylation of TSC2 and PRAS40, promoting protein synthesis and synaptic plasticity. Additional critical substrates include the transcription factor FOXO, which when phosphorylated translocates from the nucleus to the cytoplasm, preventing expression of pro-apoptotic genes. BAD phosphorylation by AKT sequesters this BH3-only protein away from BCL-2, supporting cell survival. ^{4Loss of NgBR causes neuronal damage through decreasing KAT7-mediated RFX1 acetylation and FGF1 expression.2025 · Cell Mol Life Sci · DOI 10.1007/s00018-025-05660-6 · PMID 40192836Open reference}

Role in Neurodegeneration

Alzheimer’s disease research has established clear connections between AKT dysfunction and disease pathogenesis. Amyloid-beta oligomers impair AKT signaling through increased phosphatase activity, and decreased AKT phosphorylation at Ser473 correlates with disease severity. Importantly, AKT-mediated inhibition of GSK3β is protective against tau pathology; reduced AKT activity permits unchecked GSK3β activity, contributing to tau hyperphosphorylation and NFT formation. Conversely, hyperactive mTOR signaling—downstream of AKT—has been implicated in impaired autophagy and accumulation of toxic protein aggregates.

In Parkinson’s disease, AKT signaling provides critical protection to dopaminergic neurons against alpha-synuclein toxicity and oxidative stress. Post-mortem studies reveal decreased AKT levels and phosphorylation in the substantia nigra of PD patients. PINK1 and Parkin, proteins mutated in familial PD, intersect with AKT signaling; PINK1 can phosphorylate and activate AKT, suggesting a protective pathway that is compromised in certain PD forms.

Huntington’s disease involves dysregulated AKT signaling, with evidence both supporting neuroprotective roles and indicating that excessive AKT activity may contribute to pathology. The huntingtin protein can be phosphorylated by AKT at Ser421, and this

Pathway Diagram

The following diagram shows the key molecular relationships involving AKT discovered through SciDEX knowledge graph analysis:

graph TD
    PI3K["PI3K"] -->|"upstream of"| Akt["Akt"]
    PI3K["PI3K"] -->|"part of"| Akt["Akt"]
    Ipatasertib["Ipatasertib"] -.->|"inhibits"| Akt["Akt"]
    MK2206["MK2206"] -.->|"inhibits"| Akt["Akt"]
    TSC2["TSC2"] -->|"binds"| Akt["Akt"]
    PRKCD["PRKCD"] -->|"activates"| Akt["Akt"]
    PI3K["PI3K"] -->|"activates"| Akt["Akt"]
    Akt_inhibitors["Akt inhibitors"] -.->|"inhibits"| Akt["Akt"]
    flavonoids["flavonoids"] -->|"regulates"| Akt["Akt"]
    ROS["ROS"] -->|"regulates"| Akt["Akt"]
    APOA1["APOA1"] -.->|"inhibits"| Akt["Akt"]
    TP53["TP53"] -->|"interacts with"| Akt["Akt"]
    EFNB1["EFNB1"] -->|"interacts with"| Akt["Akt"]
    SRC["SRC"] -->|"interacts with"| Akt["Akt"]
    APOE["APOE"] -.->|"inhibits"| Akt["Akt"]
    style PI3K fill:#4fc3f7,stroke:#333,color:#000
    style Akt fill:#81c784,stroke:#333,color:#000
    style Ipatasertib fill:#ff8a65,stroke:#333,color:#000
    style MK2206 fill:#ff8a65,stroke:#333,color:#000
    style TSC2 fill:#ce93d8,stroke:#333,color:#000
    style PRKCD fill:#ce93d8,stroke:#333,color:#000
    style Akt_inhibitors fill:#ff8a65,stroke:#333,color:#000
    style flavonoids fill:#ff8a65,stroke:#333,color:#000
    style ROS fill:#4fc3f7,stroke:#333,color:#000
    style APOA1 fill:#ce93d8,stroke:#333,color:#000
    style TP53 fill:#ce93d8,stroke:#333,color:#000
    style EFNB1 fill:#ce93d8,stroke:#333,color:#000
    style SRC fill:#ce93d8,stroke:#333,color:#000
    style APOE fill:#ce93d8,stroke:#333,color:#000