Calretinin also known as 29 kDa calbindin is a vitamin D-dependent calcium-binding protein

Vitamin D-dependent calcium-binding protein

Vitamin D-dependent calcium binding proteins were discovered in the cytosolic fractions of chicken intestine, and later in mammalian intestine and kidney, by workers including Robert Wasserman of Cornell University....

 involved in calcium signaling

Calcium signaling

Calcium is a common signaling mechanism, as once it enters the cytoplasm it exerts allosteric regulatory effects on many enzymes and proteins...

. In humans, the calretinin protein is encoded by the CALB2 gene

Gene

A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...

.

Function

This gene encodes an intracellular calcium-binding protein belonging to the troponin C

Troponin C

Troponin C is a part of the troponin complex. It contains four calcium-binding EF hands. It is a component of thin filaments . It contains an N lobe and a C lobe. The C lobe serves a structural purpose and binds to the N domain of TnI. The C lobe can bind either Ca2+ or Mg2+...

 superfamily. Members of this protein family have six EF-hand

EF hand

The EF hand is a helix-loop-helix structural domain found in a large family of calcium-binding proteins. The EF-hand motif contains a helix-loop-helix topology, much like the spread thumb and forefinger of the human hand, in which the Ca2+ ions are coordinated by ligands within the loop...

 domains which bind calcium. This protein plays a role in diverse cellular functions, including message targeting and intracellular calcium buffering. It also functions as a modulator of neuronal excitability, and is a diagnostic marker for some human diseases, including Hirschsprung disease and some cancers.

Calretinin is abundantly expressed in neurons and in hair follicles.

Clinical significance

Calretinin stains pleural (lung

Lung

The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...

) and peritoneal mesothelioma

Peritoneal mesothelioma

Peritoneal mesothelioma is the name given to the cancer that attacks the lining of the abdomen. This type of cancer affects the lining that protects the contents of the abdomen and which also provides a lubricating fluid to enable the organs to move and work properly.The peritoneum is made of two...

 (abdomen

Abdomen

In vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity...

) and can be used to help differentiate different lung tumour

Lung cancer

Lung cancer is a disease characterized by uncontrolled cell growth in tissues of the lung. If left untreated, this growth can spread beyond the lung in a process called metastasis into nearby tissue and, eventually, into other parts of the body. Most cancers that start in lung, known as primary...

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