akt-protein

Introduction

Akt (Protein Kinase B) is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.

Overview

AKT (Protein Kinase B, also known as PKB) is a serine/threonine kinase that serves as a central node in cell signaling, regulating cell survival, growth, proliferation, metabolism, and angiogenesis. Three AKT isoforms exist in humans: AKT1, AKT2, and AKT3, each with distinct but overlapping functions. AKT is frequently dysregulated in neurodegenerative diseases, making it an important therapeutic target (Manning & Cantley, 2007; Zhang et al., 2020). ^{1Citation2020 · DOI 10.1016/j.neuropharm.2020.108091Open reference}

--- ^{2Citation2011 · DOI 10.1016/j.neurobiolaging.2009.12.010Open reference}

Gene and Protein Structure

AKT Gene Family

Three genes encode the AKT isoforms: ^{3Citation2002 · DOI 10.1097/01.WCB.0000034373.52967.C6Open reference}

• AKT1 (ENSG00000142208): Located on chromosome 14q32.33; ubiquitously expressed

• AKT2 (ENSG00000105989): Located on chromosome 19q13.2; enriched in insulin-responsive tissues

• AKT3 (ENSG00000147883): Located on chromosome 1q43; enriched in brain

Protein Domain Architecture

AKT (~480-505 amino acids depending on isoform) contains: ^{4Citation2004 · DOI 10.1097/00001756-200404290-00008Open reference}

• PH domain (Pleckstrin Homology, residues 1-100): Binds PIP3 at the plasma membrane

• Turn motif (T308 in AKT1): Phosphorylation site for mTORC2

• Hydrophobic motif (S473 in AKT1): Phosphorylation site for mTORC2

• Kinase domain (residues 150-350): Catalytic serine/threonine kinase activity

• Regulatory domain (C-terminal): Contains hydrophobic motif

Activation Mechanism

AKT activation follows PI3K activation: ^{5Citation2021 · DOI 10.3389/fcell.2021.702015Open reference}

1. Receptor tyrosine kinases activate PI3K

2. PI3K generates PIP3 at the plasma membrane

3. AKT’s PH domain binds PIP3, localizing AKT to the membrane

4. PDK1 phosphorylates AKT at T308 (activation loop)

5. mTORC2 phosphorylates AKT at S473 (hydrophobic motif)

6. Full activation requires both phosphorylation events

--- ^{6Citation1997 · DOI 10.1016/S0092-8674(00Open reference}

Normal Biological Functions

Cell Survival and Anti-apoptosis

AKT promotes cell survival through multiple mechanisms: ^{7Citation1999 · DOI 10.1016/S0092-8674(00Open reference}

• Phosphorylates and inhibits BAD: Pro-apoptotic Bcl-2 family member (Datta et al., 1997)

• Activates NF-κB: Transcription factor for survival genes

• Inhibits caspases: Executioners of apoptosis

• Phosphorylates MDM2: Promotes p53 degradation

Cell Growth and Proliferation

AKT regulates cell growth through: ^{8Citation2011 · DOI 10.1016/j.cmet.2011.01.011Open reference}

• mTORC1 activation: Promotes protein synthesis and cell growth

• GSK3β inhibition: Stabilizes cyclin D1, promotes cell cycle progression

• FOXO phosphorylation: Inhibits forkhead transcription factors (Brunet et al., 1999)

Metabolism

AKT is a key regulator of glucose and lipid metabolism: ^{9Citation2006 · DOI 10.1111/j.1460-9568.2006.04943.xOpen reference}

• Glucose uptake: Promotes GLUT4 translocation to membrane

• Glycolysis: Increases glycolytic enzyme activity

• Glycogen synthesis: Activates glycogen synthase via GSK3β inhibition

• Lipid metabolism: Regulates SREBP and lipid synthesis (Yecies et al., 2011)

Neuronal Functions

In neurons, AKT signaling regulates: ^{10Citation2006 · DOI 10.1002/mds.20747Open reference}

• Synaptic plasticity: Important for learning and memory (Horwood et al., 2006)

• Neuronal development: Axon guidance, dendritic arborization

• Neurotrophic factor signaling: BDNF, NGF signaling

• Myelination: Oligodendrocyte survival and function

--- ^{2Citation2011 · DOI 10.1016/j.neurobiolaging.2009.12.010Open reference}0

Role in Neurodegenerative Diseases

Alzheimer’s Disease

AKT dysregulation is central to AD pathogenesis: ^{2Citation2011 · DOI 10.1016/j.neurobiolaging.2009.12.010Open reference}1

Insulin Signaling:

• AD is increasingly viewed as type 3 diabetes with brain insulin resistance

• AKT signaling is impaired in AD brain (Liu et al., 2011)

• Restoring AKT signaling improves cognitive function in AD models

Tau Pathology:

• GSK3β is a major tau kinase, inhibited by AKT

• AKT deficiency leads to increased GSK3β activity and tau hyperphosphorylation

• AKT activation reduces tau pathology in mouse models

Amyloid Metabolism:

• AKT regulates amyloid precursor protein (APP) processing

• PI3K/AKT signaling affects α-secretase activity

• Modulating AKT influences Aβ production and clearance

Synaptic Dysfunction:

• AKT is critical for synaptic plasticity and memory formation

• AKT signaling is impaired at synapses in AD

• BDNF/AKT signaling is compromised in AD brain

Parkinson’s Disease

AKT signaling is protective in PD:

Dopaminergic Neuron Survival:

• AKT protects substantia nigra dopaminergic neurons

• AKT activity is reduced in PD brain (Klein et al., 2006)

• Alpha-synuclein inhibits AKT signaling

Mitochondrial Function:

• AKT regulates mitochondrial dynamics and biogenesis

• PGC-1α activation by AKT promotes mitochondrial health

• AKT deficiency exacerbates mitochondrial dysfunction

Therapeutic Protection:

• AKT overexpression protects against MPTP/6-OHDA toxicity

• BDNF-mediated neuroprotection requires AKT signaling

Amyotrophic Lateral Sclerosis (ALS)

• AKT signaling is dysregulated in ALS motor neurons (Koshy et al., 2010)

• AKT activation protects against SOD1 mutant toxicity

• AKT/GSK3β signaling modulates motor neuron survival

• Crosstalk between AKT and TDP-43 pathology

Huntington’s Disease

• Mutant huntingtin disrupts AKT signaling (Zainuddin et al., 2011)

• AKT activity is reduced in HD models and patients

• Restoring AKT improves mitochondrial function and reduces toxicity

• AKT/mTOR signaling is impaired in HD

Therapeutic Targeting

AKT Activators

Therapeutic approaches to activate AKT signaling:

Small Molecule Activators:

• SC79: Direct AKT activator, crosses BBB

• PTEN inhibitors: Reduce PIP3 degradation

• PDK1 activators

Neurotrophic Factors:

• BDNF: Activates AKT signaling

• GDNF: Protects dopaminergic neurons via AKT

Receptor Agonists:

• Insulin and insulin mimetics

• IGF-1: Neuroprotective via AKT

Challenges

• Systemic AKT activation may promote cancer

• Isoform-specific targeting is important (AKT1 vs. AKT2 vs. AKT3)

• Brain-penetrant molecules are required

• Timing of intervention matters

Brain-Penetrant AKT Modulators

Recent drug development focuses on:

• Selective AKT isoform inhibitors/activators

• CNS-targeted compounds

• Modulators of upstream/downstream signaling

Downstream Targets

Rather than direct AKT modulation, alternative approaches:

• mTOR inhibitors/activators: Downstream of AKT

• GSK3β modulators: Major AKT substrate

• FOXO activators: Promote transcription of stress resistance genes

Pathway & Interaction Diagram

Interactive diagram showing AKT’s key relationships in the SciDEX knowledge graph (15 connections shown).

flowchart TD
    AKT(["AKT"])
    MTOR(["MTOR"])
    TSC2(["TSC2"])
    FOXO(["FOXO"])
    mTOR(["mTOR"])
    cell_growth("cell growth")
    MTORC1(["MTORC1"])
    AUTOPHAGY(["AUTOPHAGY"])
    PTEN(["PTEN"])
    LYC{"LYC"}
    CTSG(["CTSG"])
    MK2206{"MK2206"}
    PI3K(["PI3K"])
    BRSK2(["BRSK2"])
    lycopene{"lycopene"}

    AKT -->|"activates"| MTOR
    AKT -->|"phosphorylates"| TSC2
    AKT -.->|"inhibits"| TSC2
    AKT -.->|"inhibits"| FOXO
    AKT -->|"activates"| mTOR
    AKT -->|"activates"| cell_growth
    AKT -->|"activates"| MTORC1
    AKT -.->|"inhibits"| AUTOPHAGY
    PTEN -.->|"inhibits"| AKT
    LYC -.->|"inhibits"| AKT
    CTSG -.->|"inhibits"| AKT
    MK2206 -.->|"inhibits"| AKT
    PI3K -->|"activates"| AKT
    BRSK2 -->|"activates"| AKT
    lycopene -.->|"inhibits"| AKT

    style AKT fill:#006494,stroke:#4fc3f7,stroke-width:3px,color:#e0e0e0

See Also

• Proteins Index

• Genes Index

  • AKT1 Gene

  • AKT2 Gene

  • AKT3 Gene

• Diseases Index

  • Alzheimer’s Disease

  • Parkinson’s Disease

  • Amyotrophic Lateral Sclerosis

  • Huntington’s Disease

• Mechanisms Index

  • Insulin Signaling

  • PI3K/AKT Signaling

  • Apoptosis

  • mTOR Signaling

• Treatments Index

External Links

External Links

• AKT1 Gene (NCBI)

• AKT2 Gene (NCBI)

• AKT3 Gene (NCBI)

• AKT Protein (UniProt)

• AKT Signaling Pathway (KEGG)

• AKT in Neurodegeneration (PubMed)

Background

The study of Akt (Protein Kinase B) has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.

Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.