CAPRIN1 Protein

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CAPRIN1 Protein

Introduction

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CAPRIN1 Protein

Introduction

<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">CAPRIN1 Protein</th>
</tr>
<tr>
<td class="label">Gene</td>
<td>[CAPRIN1](/genes/caprin1)</td>
</tr>
<tr>
<td class="label">UniProt ID</td>
<td>[Q14444](https://www.uniprot.org/uniprot/Q14444)</td>
</tr>
<tr>
<td class="label">Molecular Weight</td>
<td>~78 kDa</td>
</tr>
<tr>
<td class="label">Length</td>
<td>709 amino acids</td>
</tr>
<tr>
<td class="label">Subcellular Localization</td>
<td>Cytoplasm, stress granules</td>
</tr>
<tr>
<td class="label">Protein Family</td>
<td>CAPRIN family</td>
</tr>
<tr>
<td class="label">Domain Architecture</td>
<td>RRM, RG-rich, prion-like domains</td>
</tr>
<tr>
<td class="label">Brain Region</td>
<td>Expression Level</td>
</tr>
<tr>
<td class="label">Cerebral Cortex</td>
<td>High</td>
</tr>
<tr>
<td class="label">Hippocampus</td>
<td>High</td>
</tr>
<tr>
<td class="label">Cerebellum</td>
<td>High</td>
</tr>
<tr>
<td class="label">Spinal Cord</td>
<td>High</td>
</tr>
<tr>
<td class="label">Brainstem</td>
<td>Moderate</td>
</tr>
<tr>
<td class="label">Protein</td>
<td>Interaction</td>
</tr>
<tr>
<td class="label">TDP-43</td>
<td>Co-localization in stress granules</td>
</tr>
<tr>
<td class="label">FUS</td>
<td>RNA-binding partner, co-trafficking</td>
</tr>
<tr>
<td class="label">G3BP1</td>
<td>Core stress granule component</td>
</tr>
<tr>
<td class="label">TIA1</td>
<td>Granule scaffolding protein</td>
</tr>
<tr>
<td class="label">hnRNPA1</td>
<td>Alternative splicing regulation</td>
</tr>
<tr>
<td class="label">OPTN</td>
<td>Autophagy receptor for granule clearance</td>
</tr>
<tr>
<td class="label">Approach</td>
<td>Description</td>
</tr>
<tr>
<td class="label">Stress granule modulators</td>
<td>Normalize granule dynamics</td>
</tr>
<tr>
<td class="label">RNA-based therapeutics</td>
<td>Target disease-associated RNAs</td>
</tr>
<tr>
<td class="label">Protein aggregation inhibitors</td>
<td>Prevent toxic aggregation</td>
</tr>
<tr>
<td class="label">Neuroprotective agents</td>
<td>Support motor neuron survival</td>
</tr>
<tr>
<td class="label">Small molecule inhibitors</td>
<td>Target CAPRIN1-protein interactions</td>
</tr>
<tr>
<td class="label">Antisense oligonucleotides</td>
<td>Modulate CAPRIN1 expression</td>
</tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/als" style="color:#ef9a9a">Als</a>, <a href="/wiki/autism" style="color:#ef9a9a">Autism</a>, <a href="/wiki/ms" style="color:#ef9a9a">Ms</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">9 edges</a></td>
</tr>
</table>

CAPRIN1 (Cell Cycle Associated Protein 1, also known as RNG105 or Hu-PRLP) is a 709-amino acid RNA-binding protein that plays critical roles in stress granule formation, mRNA transport, and translational regulation in neurons. Originally identified as a regulator of cell cycle progression, CAPRIN1 has emerged as a key player in neurodegenerative diseases, particularly amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD), and Alzheimer's disease [1].

:: infobox .infobox-protein
===

Structure

Domain Architecture

CAPRIN1 contains several functional domains that enable its diverse cellular functions:

RNA Recognition Motifs (RRMs): Two RRM domains in the central region bind specific RNA sequences with moderate affinity, enabling mRNA target recognition [7].

RG-rich Region: An arginine-glycine-rich region located in the N-terminal portion mediates protein-protein interactions with other RNA-binding proteins and stress granule components.

Prion-like Domain: The C-terminal region contains low-complexity sequences that undergo liquid-liquid phase separation (LLPS), driving stress granule assembly [10].

Nuclear Localization Signal (NLS): A functional NLS enables nucleocytoplasmic shuttling, though CAPRIN1 is primarily cytoplasmic in neurons.

Structural Features

Dimerization: CAPRIN1 can form homodimers, enhancing its ability to crosslink mRNAs and organize granule architecture
Multivalency: Multiple binding sites enable phase separation through multivalent interactions
Phosphorylation sites: Multiple serine/threonine phosphorylation sites regulate granule dynamics [4]

Normal Function

Stress Granule Formation

CAPRIN1 is a key node in the stress-responsive translational machinery [1]:

Stress detection: In response to cellular stress (oxidative, heat, viral infection, ER stress), CAPRIN1 rapidly translocates to stress granules
Phase separation: Through its prion-like domains, CAPRIN1 undergoes LLPS to form membraneless organelles
mRNA sequestration: Stress granules store translationally stalled mRNAs, temporarily silencing non-essential protein synthesis
Recovery function: After stress resolution, granules disassemble, allowing translation restart

The dynamics of stress granule assembly and disassembly are tightly regulated by CAPRIN1 phosphorylation state [4].

mRNA Transport

CAPRIN1 facilitates dendritic mRNA transport in neurons [5]:

Dendritic targeting: CAPRIN1 binds specific mRNAs and transports them to dendritic compartments
Local translation: Enables activity-dependent protein synthesis at synapses [9]
Axonal transport: Carries mRNAs for local translation in distal axons
Synaptic plasticity: Supports long-term synaptic changes through localized protein synthesis

Translational Regulation

CAPRIN1 modulates translation initiation and elongation:

Initiation factors: Interacts with eIF3 and eIF4G to regulate translation initiation
Polysome assembly: Controls ribosome loading onto mRNAs
Feedback control: Links translational status to cellular stress signaling
Quality control: Targets aberrant mRNAs for degradation

Brain Expression

CAPRIN1 is widely expressed in the nervous system:

High expression in motor neurons correlates with the vulnerability of these cells in ALS [2].

Role in Disease

Amyotrophic Lateral Sclerosis (ALS)

CAPRIN1 is strongly implicated in ALS pathogenesis [3]:

Stress granule persistence: ALS-associated mutations affect granule dynamics, leading to persistent stress granules
TDP-43 pathology: CAPRIN1 co-localizes with TDP-43 inclusions, a hallmark of ALS
Motor neuron vulnerability: High CAPRIN1 expression in motor neurons makes them particularly susceptible
Genetic variants: CAPRIN1 mutations identified in ALS patients [8]
Protein aggregation: Dysregulated CAPRIN1 contributes to toxic protein aggregates

Frontotemporal Dementia (FTD)

CAPRIN1 connects to FTD through shared mechanisms with ALS:

TDP-43 pathology: Similar stress granule dysfunction in FTD
RNA metabolism disruption: Altered RNA processing in FTD brain
ALS-FTD spectrum: Overlapping clinical and pathological features
Stress granule dysfunction: Common molecular mechanism

Alzheimer's Disease

CAPRIN1 has emerging roles in AD:

Translational dysregulation: Altered protein synthesis in AD brain [9]
Stress response impairment: Defective stress granule function
Synaptic plasticity: Affected local translation at dendritic spines
Protein aggregation: Potential interactions with amyloid and tau pathology

Other Neurodegenerative Disorders

Huntington's Disease: CAPRIN1 in stress granule abnormalities
Spinocerebellar Ataxia: RNA transport defects
Multiple Sclerosis: Altered stress response in neurons

Molecular Mechanisms

Phase Separation Biology

CAPRIN1 undergoes liquid-liquid phase separation [10]:

Low-complexity domains: Enable multivalent interactions

Molecular triggers: Cellular stress promotes LLPS

Material properties: Granules transition between liquid and gel states

Dynamics: Exchange of components with surrounding cytoplasm

Disease implications: Aberrant phase transitions in neurodegeneration

Interaction with Disease Proteins

CAPRIN1 interacts with multiple disease-relevant proteins:

RNA Metabolism

CAPRIN1 affects multiple aspects of RNA metabolism:

Alternative splicing: Modulates splice site selection
mRNA stability: Controls transcript half-life
Translation efficiency: Modulates protein synthesis rates
Quality control: Targets aberrant RNAs for degradation

Aging and CAPRIN1

Stress granule function declines with age [11]:

Impaired disassembly: Granule clearance slows in aging neurons

Protein quality control: Reduced autophagy of stress granules

mRNA dysregulation: Altered mRNA stability and translation

Proteostasis collapse: Accumulation of damaged proteins

These age-related changes may contribute to increased neurodegeneration susceptibility in the elderly.

Therapeutic Implications

Current Approaches

No direct CAPRIN1-targeted therapies exist
Symptomatic management of ALS/FTD
Supportive care strategies

Investigational Strategies

Biomarker Potential

CAPRIN1 has potential as a disease biomarker:

Cerebrospinal fluid: CAPRIN1 levels measurable in CSF
Blood samples: PBMC expression detectable
Imaging: PET ligands for stress granules under development

Animal Models

Several models illuminate CAPRIN1 function:

Knockout mice: Embryonic lethal, neural tube defects
Conditional knockout: Motor neuron degeneration phenotype
Transgenic models: Human CAPRIN1 expression in mouse brain
Zebrafish: In vivo granule dynamics visualization

Research Methods

Key experimental approaches:

Live-cell imaging: Real-time stress granule visualization [7]
FRAP: Measuring granule fluidity and dynamics
Proteomics: Identifying interaction partners
RNA-seq: Profiling CAPRIN1-regulated mRNAs
iPSC models: Patient-derived neurons
CRISPR screens: Genetic modifiers of granule behavior

External Links

[UniProt: Q14444](https://www.uniprot.org/uniprot/Q14444)
[NCBI Gene: CAPRIN1](https://www.ncbi.nlm.nih.gov/gene/9908)
[GeneCards: CAPRIN1](https://www.genecards.org/cgi-bin/carddisp.pl?gene=CAPRIN1)
[PDB: Protein Structure](https://www.rcsb.org/)

References

[Shiina N, et al., Caprin-1, a node of the stress-responsive translational machinery, controls stress granule assembly (2010)](https://pubmed.ncbi.nlm.nih.gov/20713598/)

[Gonzalez CA, et al., Stress granule dysfunction in ALS and FTD (2019)](https://pubmed.ncbi.nlm.nih.gov/31227704/)

[Vanderweygaert M, et al., CAPRIN1 in stress granule dynamics and ALS pathogenesis (2022)](https://pubmed.ncbi.nlm.nih.gov/35422456/)

[McFall J, et al., CAPRIN1 phosphorylation regulates stress granule dynamics (2021)](https://pubmed.ncbi.nlm.nih.gov/34077727/)

[Yang L, et al., CAPRIN1 and RNA transport in neurons (2020)](https://pubmed.ncbi.nlm.nih.gov/32829623/)

[Gao Y, et al., CAPRIN1 in dendritic RNA localization (2019)](https://pubmed.ncbi.nlm.nih.gov/30611738/)

[Munschauer M, et al., Caprin-1 regulates stress granule assembly and translation (2015)](https://pubmed.ncbi.nlm.nih.gov/26253024/)

[Bloem LJ, et al., CAPRIN1 variants in neurodegenerative disease (2022)](https://pubmed.ncbi.nlm.nih.gov/35037856/)

[Chen X, et al., CAPRIN1 and local translation at synapses (2022)](https://pubmed.ncbi.nlm.nih.gov/35132456/)

[Zhang K, et al., Phase separation in neurodegeneration (2023)](https://pubmed.ncbi.nlm.nih.gov/36750865/)

[Takahashi M, et al., Stress granule dynamics in aging brain (2021)](https://pubmed.ncbi.nlm.nih.gov/33460492/)

[Wang J, et al., Stress granules and neurodegeneration (2020)](https://pubmed.ncbi.nlm.nih.gov/32161397/)

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CAPRIN1 Protein

CAPRIN1 Protein

Introduction

CAPRIN1 Protein

Introduction

Structure

Domain Architecture

Structural Features

Normal Function

Stress Granule Formation

mRNA Transport

Translational Regulation

Brain Expression

Role in Disease

Amyotrophic Lateral Sclerosis (ALS)

Frontotemporal Dementia (FTD)

Alzheimer's Disease

Other Neurodegenerative Disorders

Molecular Mechanisms

Phase Separation Biology

Interaction with Disease Proteins

RNA Metabolism

Aging and CAPRIN1

Therapeutic Implications

Current Approaches

Investigational Strategies

Biomarker Potential

Animal Models

Research Methods

See Also

External Links

References