ACTB Protein

ACTB Protein — Beta-Actin

<div class="infobox infobox-protein">
<table>
<tr><th colspan="2" style="background:#e8f4f8; text-align:center; font-size:1.1em;">ACTB Protein</th></tr> [@michele2021]
<tr><td><strong>Protein Name</strong></td><td>Beta-Actin</td></tr> [@rivire2012]
<tr><td><strong>Gene</strong></td><td>[ACTB](/genes/actb)</td></tr> [@maloney2012]
<tr><td><strong>UniProt ID</strong></td><td>[P60709](https://www.uniprot.org/uniprot/P60709)</td></tr> [@shults2005]
<tr><td><strong>PDB ID</strong></td><td>1j6z, 2bt0, 3hku</td></tr> [@kim2010]
<tr><td><strong>Molecular Weight</strong></td><td>~42 kDa</td></tr>
<tr><td><strong>Subcellular Localization</strong></td><td>Cytoskeleton (cortical, stress fibers)</td></tr>
<tr><td><strong>Protein Family</strong></td><td>Actin family</td></tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/ad" style="color:#ef9a9a">AD</a>, <a href="/wiki/adh" style="color:#ef9a9a">ADH</a>, <a href="/wiki/ali" style="color:#ef9a9a">ALI</a>, <a href="/wiki/als" style="color:#ef9a9a">ALS</a>, <a href="/wiki/alzheimer" style="color:#ef9a9a">ALZHEIMER</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">668 edges</a></td>
</tr>
</table>
</div>

Overview

ACTB Protein — Beta-Actin

<div class="infobox infobox-protein">
<table>
<tr><th colspan="2" style="background:#e8f4f8; text-align:center; font-size:1.1em;">ACTB Protein</th></tr> [@michele2021]
<tr><td><strong>Protein Name</strong></td><td>Beta-Actin</td></tr> [@rivire2012]
<tr><td><strong>Gene</strong></td><td>[ACTB](/genes/actb)</td></tr> [@maloney2012]
<tr><td><strong>UniProt ID</strong></td><td>[P60709](https://www.uniprot.org/uniprot/P60709)</td></tr> [@shults2005]
<tr><td><strong>PDB ID</strong></td><td>1j6z, 2bt0, 3hku</td></tr> [@kim2010]
<tr><td><strong>Molecular Weight</strong></td><td>~42 kDa</td></tr>
<tr><td><strong>Subcellular Localization</strong></td><td>Cytoskeleton (cortical, stress fibers)</td></tr>
<tr><td><strong>Protein Family</strong></td><td>Actin family</td></tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/ad" style="color:#ef9a9a">AD</a>, <a href="/wiki/adh" style="color:#ef9a9a">ADH</a>, <a href="/wiki/ali" style="color:#ef9a9a">ALI</a>, <a href="/wiki/als" style="color:#ef9a9a">ALS</a>, <a href="/wiki/alzheimer" style="color:#ef9a9a">ALZHEIMER</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">668 edges</a></td>
</tr>
</table>
</div>

Overview

ACTB (Beta-Actin) is a highly conserved cytoskeletal protein encoded by the ACTB gene located on chromosome 7p15 [1]. As one of the six actin isoforms in humans, β-actin is ubiquitously expressed in virtually all cell types and serves as a fundamental component of the cytoskeleton. The protein undergoes dynamic polymerization and depolymerization, forming filamentous actin (F-actin) structures that are essential for cell structure, motility, division, and intracellular transport [2]. Beyond its structural roles, β-actin participates in critical cellular processes including gene transcription, chromatin remodeling, and intracellular signaling. Mutations in ACTB are associated with neurodevelopmental disorders, and dysregulated actin dynamics contribute to the pathogenesis of neurodegenerative diseases including [Alzheimer's disease](/diseases/alzheimers-disease), [Parkinson's disease](/diseases/parkinsons-disease), and ALS [3].

Structure

β-Actin is a 375-amino acid globular protein with a characteristic actin fold:

Primary Structure

• Amino Acids: 375 residues
• Molecular Weight: ~42 kDa
• Isoelectric Point: pH 5.2

Tertiary Structure

• Nucleotide-Binding Domain: Binds ATP (G-actin) or ADP (F-actin)
• DNase I Binding Loop: Highly conserved region involved in polymerization
• Hydrophobic Loop: Interacts with myosin
• C-terminal Domain: Contains binding sites for regulatory proteins

Quaternary Structure

• Monomeric (G-actin): Globular form, ATP-bound
• Filamentous (F-actin): Polymeric form, ADP-bound
• Binding Proteins: Thymosin β4, profilin, cofilin

• N-terminal acetylation (essential for polymerization)
• Arginine methylation
• Tyrosine nitration
• Ubiquitination

Normal Function

Cytoskeletal Structure

β-Actin forms the core of the actin cytoskeleton:

Cellular Architecture:

• Cortical actin beneath plasma membrane
• Stress fibers across the cell
• Lamellipodia and filopodia extensions
• Cytoplasmic actin networks

• Maintains cell morphology
• Establishes cell polarity
• Supports membrane organization

Cell Motility

Actin polymerization drives cell movement:

• Lamellipodia: Broad, sheet-like protrusions at leading edge
• Filopodia: Thin, finger-like extensions
• Cell Migration: Coordinated actin-myosin contraction
• Chemotaxis: Directed movement in response to gradients

Cell Division

Actin dynamics are essential for mitosis and cytokinesis:

• Mitotic Spindle Positioning: Actin [cortex](/brain-regions/cortex) regulates spindle orientation
• Cleavage Furrow Formation: Contractile ring at cell equator
• Cytokinesis: Physical separation of daughter cells

Intracellular Transport

β-Actin tracks support organelle and vesicle movement:

• Myosin-Dependent Transport: Cargo movement along actin filaments
• Endocytosis and Exocytosis: Vesicle trafficking
• Cytoplasmic Streaming: Large-scale cytoplasmic movement

Nuclear Functions

β-Actin participates in nuclear processes:

• Chromatin Remodeling: Component of BAF complex
• Transcription: RNA polymerase I and II function
• Nuclear Export: Exportin-mediated transport
• DNA Repair: Access to damaged sites

Role in Disease

Baraitser-Winter Syndrome

Dominant ACTB mutations cause Baraitser-Winter syndrome (BRWS) [4]:

Clinical Features:

• Iris coloboma
• Deafness
• Developmental delay
• Characteristic facial features
• Brain malformations (pachygyria, lissencephaly)

• Disrupted actin polymerization
• Impaired cell migration during development
• Altered neuronal morphology

Neurodevelopmental Disorders

ACTB mutations contribute to neurodevelopmental conditions:

Intellectual Disability:

• Impaired synaptic plasticity
• Altered dendritic spine morphology
• Defective neuronal connectivity

• Social and communication deficits
• Repetitive behaviors
• Synaptic dysfunction

Alzheimer's Disease

β-Actin dysregulation contributes to AD pathogenesis [5]:

Amyloid-β Effects:

• Disrupts actin polymerization
• Impairs synaptic actin dynamics
• Reduces spine density

• Tau interacts with actin
• Alters cytoskeletal stability
• Promotes neurofibrillary tangles

• Actin-stabilizing compounds show promise
• Targeting actin-regulatory proteins
• Restoring synaptic plasticity

Parkinson's Disease

Actin dysfunction contributes to PD mechanisms [6]:

Dopaminergic Neuron Vulnerability:

• Impaired axonal transport
• Altered dendritic complexity
• Reduced synaptic connectivity

• α-Synuclein binds actin
• Disrupts actin filament formation
• Promotes aggregation

• Actin-modulating compounds
• Myosin inhibitors
• Cytoskeletal stabilizers

Amyotrophic Lateral Sclerosis (ALS)

Actin pathology in ALS [7]:

[TDP-43](/mechanisms/tdp-43-proteinopathy) Aggregation:

• TDP-43 interacts with actin
• Disrupted RNA transport
• Impaired synaptic function

• Dysregulated actin dynamics
• Impaired vesicle trafficking
• Motor neuron vulnerability

Cancer

β-Actin is dysregulated in various cancers:

Metastasis:

• Enhanced cell motility
• Invasion through basement membrane
• Circulating tumor cells

• Altered drug response
• Stem cell-like properties
• Epithelial-mesenchymal transition

Interacting Partners

| Protein | Interaction Type | Functional Significance |
|---------|------------------|------------------------|
| Myosin II | Motor protein | Contraction, motility |
| Profilin | Binding protein | Actin polymerization |
| Cofilin | Binding protein | Filament turnover |
| α-Synuclein | Pathological | PD progression |
| Tau | Pathological | AD progression |
| BAF Complex | Chromatin | Gene expression |

Therapeutic Approaches

Targeting β-actin and actin dynamics for disease treatment:

Biomarkers

β-Actin serves as a reference gene and potential biomarker:

• Housekeeping Gene: Standard for qPCR normalization
• Circulating Actin: Biomarker for tissue damage
• Disease Progression: Correlates with severity in some conditions

Pathway & Interaction Diagram

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

See Also

• [ACTB Gene](/genes/actb)
• [Cytoskeleton in Neurodegeneration](/mechanisms/cytoskeleton-neurodegeneration)
• [Axonal Transport](/mechanisms/axonal-transport)
• [Synaptic Dysfunction](/mechanisms/synaptic-dysfunction)
• [Baraitser-Winter Syndrome](/diseases/baraitser-winter-syndrome)

External Links

• [UniProt P60709](https://www.uniprot.org/uniprot/P60709)
• [PDB: Actin Structure](https://www.rcsb.org/structure/1j6z)
• [GeneCards ACTB](https://www.genecards.org/cgi-bin/carddisp.pl?gene=ACTB)
• [NIH Actin Database](https://www.ncbi.nlm.nih.gov/gene/81)

References