title: Calretinin - Calretinin
category: protein
Calretinin
Introduction
Calretinin Calretinin is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes. [@hof1999]
<div class="infobox infobox-protein">
<table>
<tr><th colspan="2" style="background:#e8f4f8; text-align:center; font-size:1.1em;">Calretinin</th></tr>
<tr><td><strong>Protein Name</strong></td><td>Calretinin</td></tr>
<tr><td><strong>Gene</strong></td><td>[CALB2](/genes/calb2)</td></tr>
<tr><td><strong>UniProt ID</strong></td><td>[P22676](https://www.uniprot.org/uniprot/P22676)</td></tr>
<tr><td><strong>PDB ID</strong></td><td>1T5L</td></tr>
<tr><td><strong>Molecular Weight</strong></td><td>31 kDa</td></tr>
<tr><td><strong>Localization</strong></td><td>Cytosol</td></tr>
<tr><td><strong>Protein Family</strong></td><td>EF-hand calcium-binding proteins</td></tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/autoimmune" style="color:#ef9a9a">Autoimmune</a>, <a href="/wiki/cancer" style="color:#ef9a9a">Cancer</a>, <a href="/wiki/depression" style="color:#ef9a9a">Depression</a>, <a href="/wiki/ms" style="color:#ef9a9a">Ms</a>, <a href="/wiki/schizophrenia" style="color:#ef9a9a">Schizophrenia</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">12 edges</a></td>
</tr>
</table>
</div>
Overview
...title: Calretinin - Calretinin
category: protein
Calretinin
Introduction
Calretinin Calretinin is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes. [@hof1999]
<div class="infobox infobox-protein">
<table>
<tr><th colspan="2" style="background:#e8f4f8; text-align:center; font-size:1.1em;">Calretinin</th></tr>
<tr><td><strong>Protein Name</strong></td><td>Calretinin</td></tr>
<tr><td><strong>Gene</strong></td><td>[CALB2](/genes/calb2)</td></tr>
<tr><td><strong>UniProt ID</strong></td><td>[P22676](https://www.uniprot.org/uniprot/P22676)</td></tr>
<tr><td><strong>PDB ID</strong></td><td>1T5L</td></tr>
<tr><td><strong>Molecular Weight</strong></td><td>31 kDa</td></tr>
<tr><td><strong>Localization</strong></td><td>Cytosol</td></tr>
<tr><td><strong>Protein Family</strong></td><td>EF-hand calcium-binding proteins</td></tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/autoimmune" style="color:#ef9a9a">Autoimmune</a>, <a href="/wiki/cancer" style="color:#ef9a9a">Cancer</a>, <a href="/wiki/depression" style="color:#ef9a9a">Depression</a>, <a href="/wiki/ms" style="color:#ef9a9a">Ms</a>, <a href="/wiki/schizophrenia" style="color:#ef9a9a">Schizophrenia</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">12 edges</a></td>
</tr>
</table>
</div>
Overview
Calretinin (encoded by the [CALB2](/genes/calb2) gene) is a calcium-binding protein belonging to the EF-hand family of proteins. It contains 6 EF-hand motifs and has a molecular weight of approximately 31 kDa. Calretinin is primarily expressed in specific populations of [GABAergic interneurons](/cell-types/gabaergic-neurons) throughout the central nervous system, particularly in the [cortex](/brain-regions/cortex), [hippocampus](/brain-regions/hippocampus), and [cerebellum](/brain-regions/cerebellum).
Calretinin serves as a reliable immunohistochemical marker for identifying specific interneuron subsets due to its highly restricted expression pattern. It is considered a calcium buffer with high affinity for calcium ions.
Structure
Calretinin possesses six EF-hand calcium-binding motifs:
- Five functional EF-hands capable of binding calcium
- High-affinity calcium binding properties
- Protein structure stabilized by hydrophobic core interactions
- Dimerization capability under certain conditions
The three-dimensional structure has been solved (PDB: 1T5L), revealing the characteristic EF-hand fold common to all calcium-binding proteins in this family.
Normal Function
Calcium Buffering
Calretinin functions as a high-affinity calcium buffer in [neurons](/entities/neurons):
- Protects neurons from calcium overload
- Modulates calcium signaling kinetics
- Shapes synaptic plasticity
Neuronal Marker
Calretinin is expressed in specific [interneuron](/cell-types/cortical-interneurons) populations:
- [Cortex](/brain-regions/cortex) layer 2/3 interneurons
- [Hippocampal](/brain-regions/hippocampus) interneurons
- Cerebellar granule cells
- Subpopulations of [medium spiny neurons](/cell-types/medium-spiny-neurons)
Synaptic Modulation
Calretinin modulates synaptic transmission:
- Influences GABA release
- Affects postsynaptic calcium dynamics
- May play roles in network oscillations
Role in Neurodegenerative Diseases
Alzheimer's Disease
Calretinin-expressing neurons show notable resilience in [Alzheimer's disease](/diseases/alzheimers-disease):
- Calretinin-positive (CR+ interneurons](/cell-types/calretinin-interneurons) are relatively preserved compared to other interneuron populations
- These neurons may be resistant to amyloid toxicity
- Potential protective mechanisms include:
- Enhanced calcium homeostasis
- Lower metabolic demands
- Distinctive electrophysiological properties
The relative preservation of CR+ neurons makes them of interest for understanding selective vulnerability in [neurodegeneration](/diseases/neurodegeneration).
Parkinson's Disease
Calretinin expression in [Parkinson's disease](/diseases/parkinsons-disease):
- Altered expression patterns observed in some studies
- Potential involvement in basal ganglia circuitry
- May affect [dopaminergic](/cell-types/dopaminergic-neurons) neuron function
Schizophrenia
Calretinin alterations in [schizophrenia](/diseases/schizophrenia):
- Changes in CR+ neuron density reported
- Potential role in circuit dysfunction
- Linked to gamma oscillation abnormalities
Other Neurological Conditions
- Huntington's Disease: Variable expression changes
- Epilepsy: Altered calretinin in seizure contexts
- Autism Spectrum Disorders: Some studies report differences
Therapeutic Implications
Calretinin has attracted attention for therapeutic development:
Neuroprotective Strategies: Understanding why CR+ neurons resist degeneration could inform protective therapies
Cell Replacement Therapy: CR+ interneurons as candidates for [cell-based therapies](/therapeutics/cell-therapy-neurodegeneration)
Biomarker Potential: Calretinin as a marker for specific neuron populations in disease statesResearch Methods
Calretinin is widely used in research:
- Immunohistochemistry: Primary marker for CR+ neurons
- Transgenic Models: Reporter lines for studying interneuron populations
- Single-cell RNA-seq: Marker gene for interneuron classification
Background
The study of Calretinin Calretinin 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.
See Also
- Gene: CALB2
- [Cell Types: Calretinin Interneurons](/content/cell-types)
- [Cell Types: Calretinin Neurons](/content/cell-types)
- [Proteins: Calbindin (related EF-hand protein)](/content/proteins)
- [Proteins: Parvalbumin (related calcium-binding protein)](/content/proteins)
- [Mechanisms: Calcium Signaling in Neurodegeneration](/content/mechanisms)
External Links
- [UniProt: Calretinin (P22676)](https://www.uniprot.org/uniprot/P22676)
- [PDB: Calretinin Structure (1T5L)](https://www.ebi.ac.uk/pdbe/alpha/1T5L)
- [Human Protein Atlas: CALB2](https://www.proteinatlas.org/ENSG00000176619-CALB2)
References
[Rogers et al., (1988). Calretinin: a calcium-binding protein in the CNS. J Neurosci (1988)](https://pubmed.ncbi.nlm.nih.gov/3266781/))
[Schwaller et al., (2002). Calretinin, calbindin D-28k and parvalbumin in the rat peripheral nervous system. Neuroscience (2002)](https://doi.org/10.1016/S0306-4522(02))
[Gulyás et al., (1996). Calretinin is present in GABA-containing non-pyramidal cells of the rat hippocampus. Hippocampus (1996)](https://doi.org/10.1002/(SICI))
[Ferrer et al., (1994). Calretinin in neurodegenerative processes. J Neural Transm Suppl (1994)](https://pubmed.ncbi.nlm.nih.gov/7966314/))
[Hof et al., (1999). Calretinin-immunoreactive neurons and their fate in aging and Alzheimer's disease. J Comp Neurol (1999)](https://doi.org/10.1002/(SICI))