Calpastatin (CAST)
The protein contains 708 amino acids for an estimated molecular weight of 76573 Da.
Specific inhibition of calpain (calcium-dependent cysteine protease). Plays a key role in postmortem tenderization of meat and have been proposed to be involved in muscle protein degradation in living tissue. (updated: March 4, 2015)
Protein identification was indicated in the following studies:
- Goodman and co-workers. (2013) The proteomics and interactomics of human erythrocytes. Exp Biol Med (Maywood) 238(5), 509-518.
- Lange and co-workers. (2014) Annotating N termini for the human proteome project: N termini and Nα-acetylation status differentiate stable cleaved protein species from degradation remnants in the human erythrocyte proteome. J Proteome Res. 13(4), 2028-2044.
- Hegedűs and co-workers. (2015) Inconsistencies in the red blood cell membrane proteome analysis: generation of a database for research and diagnostic applications. Database (Oxford) 1-8.
- Bryk and co-workers. (2017) Quantitative Analysis of Human Red Blood Cell Proteome. J Proteome Res. 16(8), 2752-2761.
- D'Alessandro and co-workers. (2017) Red blood cell proteomics update: is there more to discover? Blood Transfus. 15(2), 182-187.
Methods
The following articles were analysed to gather the proteome content of erythrocytes.
The gene or protein list provided in the studies were processed using the ID mapping API of Uniprot in September 2018. The number of proteins identified and mapped without ambiguity in these studies is indicated below.
Only Swiss-Prot entries (reviewed) were considered for protein evidence assignation.
| Publication | Identification 1 | Uniprot mapping 2 | Not mapped / Obsolete | TrEMBL | Swiss-Prot |
|---|---|---|---|---|---|
| Goodman (2013) | 2289 (gene list) | 2278 | 53 | 20599 | 2269 |
| Lange (2014) | 1234 | 1234 | 7 | 28 | 1224 |
| Hegedus (2015) | 2638 | 2622 | 0 | 235 | 2387 |
| Wilson (2016) | 1658 | 1528 | 170 | 291 | 1068 |
| d'Alessandro (2017) | 1826 | 1817 | 2 | 0 | 1815 |
| Bryk (2017) | 2090 | 2060 | 10 | 108 | 1942 |
| Chu (2018) | 1853 | 1804 | 55 | 362 | 1387 |
1 as available in the article and/or in supplementary material
2 uniprot mapping returns all protein isoforms as one entry
The compilation of older studies can be retrieved from the Red Blood Cell Collection database.
The data and differentiation stages presented below come from the proteomic study and analysis performed by our partners of the GReX consortium, more details are available in their published work.
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| Variant | Description |
|---|---|
| dbSNP:rs1643702 | |
| dbSNP:rs754615 | |
| dbSNP:rs4948 | |
| empty |
The reference OMIM entry for this protein is 114090
Calpastatin; cast
DESCRIPTION
Calpastatin is an endogenous inhibitor of calpains (see 114170) consisting of 4 inhibitory repeats, each of which neutralizes an activated calpain. Unlike proteinases, it is an intrinsically unstructured protein, adopting a defined structure only upon binding to active calpain (Moldoveanu et al., 2008; Hanna et al., 2008).GENE FUNCTION
In erythrocytes of patients with essential hypertension (see 145500), the level of calpastatin activity is significantly lower than in the red cells of normotensive subjects. Pontremoli et al. (1988) demonstrated by Western blot analysis that the decreased inhibitor activity is the result of a decrease in the amount of the inhibitor protein. Calpastatin isolated and purified from erythrocytes of normotensive and hypertensive patients had identical specific activities. Pontremoli et al. (1988) also presented evidence indicating that the decreased level of calpastatin cannot be ascribed to accelerated decay during the red cell life span. Mimori et al. (1995) demonstrated that anti-calpastatin autoantibodies are present in as many as 57% of rheumatoid arthritis patients and concluded that they may participate in pathogenic mechanisms of this and other rheumatic diseases which showed a lower frequency. Lin et al. (2015) performed siRNA-mediated knockdown of CAST in the HaCaT immortalized keratinocyte cell line. Immunocytochemical analysis before and after mechanical stress revealed breakage of intercellular connections in CAST-knockdown cell monolayers, independent of whether they had been subjected to mechanical stress. In contrast, control cells showed stretched keratin filaments after mechanical stress but no disruption in intercellular adhesion prior to stress. Lin et al. (2015) concluded that calpastatin plays a role in keratinocyte adhesion.BIOCHEMICAL FEATURES
- Crystal Structure Moldoveanu et al. (2008) reported the 3.0-angstrom crystal structure of calcium-bound m-calpain (CAPN2; 114230) in complex with the first calpastatin repeat, both from rat, revealing the mechanism of exclusive specificity. The structure highlighted the complexity of calpain activation by calcium, illustrating key residues in a peripheral domain that serve to stabilize the protease core on calcium binding. Fully activated calpain binds 10 Ca(2+) atoms, resulting in several conformational changes allowing recognition by calpastatin. Calpain inhibition is mediated by the intimate contact with 3 critical regions of calpastatin. Two regions target the penta-EF-hand domains of calpain, and the third occupies the substrate-binding cleft, projecting a loop around the active site thiol to evade proteolysis. Hanna et al. (2008) reported the 2.4-angstrom resolution crystal structure of the calcium-bound calpain-2 (m-calpain) heterodimer bound by 1 of the 4 inhibitory domains of calpastatin. They observed that calpastatin inhibits calpain by occupying both sides of the active site cleft. Although the inhibitor passes through the active site cleft it escapes cleavage in a novel manner by looping out and around the active site cysteine. The inhibitory domain of calpastatin recognizes multiple lower affinity sites present only in the calcium-bound form of the enzyme, resulting in an interaction that is tight, specific, and calcium-dependent. Hanna et al. (2008) concluded that this crystal structure, and that of the related complex described by Moldoveanu et al. (2008), also revealed the conforma ... More on the omim web site
Feb. 2, 2018: Protein entry updated
Automatic update: Uniprot description updated
Dec. 19, 2017: Protein entry updated
Automatic update: Uniprot description updated
Nov. 23, 2017: Protein entry updated
Automatic update: Uniprot description updated
March 16, 2016: Protein entry updated
Automatic update: OMIM entry 114090 was added.