Calretinin

Not to be confused with calreticulin.

Calbindin 2
Identifiers
Symbols	CALB2 ; CAB29; CAL2; CR
External IDs	OMIM: 114051 MGI: 101914 HomoloGene: 1318 GeneCards: CALB2 Gene
Gene ontology Molecular function • calcium ion binding Cellular component • nucleus • cytoplasm • cytosol • gap junction • neuron projection • terminal bouton • synapse Biological process • cytosolic calcium ion homeostasis Sources: Amigo / QuickGO
Orthologs
Species	Human	Mouse
Entrez	794	12308
Ensembl	ENSG00000172137	ENSMUSG00000003657
UniProt	P22676	Q08331
RefSeq (mRNA)	NM_001740	NM_007586
RefSeq (protein)	NP_001731	NP_031612
Location (UCSC)	Chr 16: 71.36 – 71.39 Mb	Chr 8: 110.14 – 110.17 Mb
PubMed search	[1]	[2]

Micrograph of a malignant epithelioid mesothelioma stained with an antibody against calretinin.

Calretinin also known as 29 kDa calbindin is a calcium-binding protein involved in calcium signaling. In humans, the calretinin protein is encoded by the CALB2 gene.

Function

This gene encodes an intracellular calcium-binding protein belonging to the troponin C superfamily. Members of this protein family have six EF-hand domains which bind calcium. This protein plays a role in diverse cellular functions, including message targeting and intracellular calcium buffering.

Calretinin is abundantly expressed in neurons including retina (which gave it the name) and cortical interneurons. Expression was found in different neurons than that of the similar vitamin D-dependent calcium-binding protein, calbindin-28kDa.

Calretinin has an important role as a modulator of neuronal excitability including the induction of long-term potentiation. Loss of expression of calretinin in hippocampal interneurons has been suggested to be relevant in temporal lobe epilepsy.

It is expressed in a number of other locations including hair follicles.

Clinical significance

Calretinin is a diagnostic marker for some human diseases, including Hirschsprung disease and some cancers.

Mesothelioma

Using immunohistochemistry, calretinin can be demonstrated in both benign mesothelium and in malignant mesothelioma and can be used to help differentiate different lung tumours. Antibodies to calretinin can also be used to distinguish between different types of brain tumour, demonstrating only those with neuronal rather than glial, differentiation.

Hirschsprung disease

In Hirschsprung disease, calretinin immunohistochemistry offers additional diagnostic value in specimens with inadequate amount of submucosa and rarely seen ganglion cells. The presence of ganglion cells consistently correlated with calretinin-positive thin nerve fibrils in the lamina propria, muscularis mucosae and superficial submucosa. These calretinin-positive thin neurofibrils are absent in the aganglionic segments of bowel and in the areas without ganglion cells from the junction of normal with diseased rectum. Calretinin is strongly expressed in the submucosal and subserosal nerve trunks in the ganglionic segment. No calretinin expression is seen in the nerve trunks in the rest of the aganglionic segment. It has faint expression in the thick nerve trunks from the areas without ganglion cells. Faint positivity of the thick submucosal and subserosal nerves in the absence of ganglion cells and calretinin positive nerve fibrils, is characteristic of the junction of the aganglionic-to-normal rectum.

External links

• calretinin at the US National Library of Medicine Medical Subject Headings (MeSH)

This article incorporates text from the United States National Library of Medicine, which is in the public domain.