CRYAB

CRYAB
Available structures PDB Ortholog search: PDBe RCSB List of PDB id codes 2KLR, 2N0K, 2WJ7, 2Y1Y, 2Y1Z, 2Y22, 2YGD, 3L1G, 3SGM, 3SGN, 3SGO, 3SGP, 3SGR, 3SGS, 4M5S, 4M5T, 3J07
Identifiers
Aliases	CRYAB, CMD1II, CRYA2, CTPP2, CTRCT16, HEL-S-101, HSPB5, MFM2, crystallin alpha B
External IDs	OMIM: 123590 MGI: 88516 HomoloGene: 68209 GeneCards: CRYAB
Gene location (Human) Chr. Chromosome 11 (human)[1] Band 11q23.1 Start 111,908,564 bp[1] End 111,923,722 bp[1]
Gene location (Mouse) Chr. Chromosome 9 (mouse)[2] Band 9 A5.3|9 27.75 cM Start 50,662,625 bp[2] End 50,667,936 bp[2]
RNA expression pattern Bgee Human Mouse (ortholog) Top expressed in middle frontal gyrus olfactory bulb optic nerve inferior ganglion of vagus nerve right ventricle gastrocnemius muscle tibialis anterior muscle internal globus pallidus body of tongue tibial nerve Top expressed in ciliary body iris myocardium of ventricle soleus muscle sciatic nerve intercostal muscle retinal pigment epithelium masseter muscle extraocular muscle right ventricle More reference expression data BioGPS More reference expression data
Gene ontology Molecular function protein homodimerization activity microtubule binding unfolded protein binding metal ion binding cytoskeletal protein binding protein binding structural constituent of eye lens identical protein binding amyloid-beta binding protein-containing complex binding Cellular component cytoplasm Golgi apparatus I band microtubule cytoskeleton nucleoplasm cell surface actin filament bundle extracellular exosome nucleus cardiac myofibril perikaryon dendritic spine synaptic membrane synapse M band postsynaptic density axon mitochondrion cytosol plasma membrane Z disc contractile fiber protein-containing complex Biological process negative regulation of intracellular transport response to estradiol muscle contraction regulation of cell death human ageing negative regulation of apoptotic process microtubule polymerization or depolymerization protein folding stress-activated MAPK cascade negative regulation of cell growth cellular response to gamma radiation regulation of cellular response to heat negative regulation of reactive oxygen species metabolic process protein homooligomerization response to hydrogen peroxide response to hypoxia lens development in camera-type eye tubulin complex assembly muscle organ development multicellular organism aging negative regulation of gene expression negative regulation of protein homooligomerization camera-type eye development negative regulation of cysteine-type endopeptidase activity involved in apoptotic process protein stabilization apoptotic process involved in morphogenesis negative regulation of amyloid fibril formation negative regulation of transcription, DNA-templated Sources:Amigo / QuickGO
Orthologs Species Human Mouse Entrez 1410 12955 Ensembl ENSG00000109846 ENSMUSG00000032060 UniProt P02511 P23927 RefSeq (mRNA) NM_001289807 NM_001289808 NM_001885 NM_001330379 NM_001368245 NM_001368246 NM_001289782 NM_001289784 NM_001289785 NM_009964 RefSeq (protein) NP_001276736 NP_001276737 NP_001317308 NP_001876 NP_001355174 NP_001355175 NP_001276711 NP_001276713 NP_001276714 NP_034094 Location (UCSC) Chr 11: 111.91 – 111.92 Mb Chr 9: 50.66 – 50.67 Mb PubMed search [3] [4]
Wikidata
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Alpha-crystallin B chain is a protein that in humans is encoded by the CRYAB gene.^[5] It is part of the small heat shock protein family and functions as molecular chaperone that primarily binds misfolded proteins to prevent protein aggregation, as well as inhibit apoptosis and contribute to intracellular architecture.^[6][7][8] Post-translational modifications decrease the ability to chaperone.^[6][8] Mutations in CRYAB cause different cardiomyopathies,^[9] skeletal myopathies^[10] mainly myofibrillar myopathy,^[11] and also cataracts.^[12] In addition, defects in this gene/protein have been associated with cancer and neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease.^[6][7][8]

Structure

Crystallins are separated into two classes: taxon-specific, or enzyme, and ubiquitous. The latter class constitutes the major proteins of vertebrate eye lens and maintains the transparency and refractive index of the lens. Since lens central fiber cells lose their nuclei during development, these crystallins are made and then retained throughout life, making them extremely stable proteins. Mammalian lens crystallins are divided into alpha, beta, and gamma families; beta and gamma crystallins are also considered as a superfamily. Alpha and beta families are further divided into acidic and basic groups.

Seven protein regions exist in crystallins: four homologous motifs, a connecting peptide, and N- and C-terminal extensions. Alpha crystallins are composed of two gene products: alpha-A and alpha-B, for acidic and basic, respectively. These heterogeneous aggregates consist of 30–40 subunits; the alpha-A and alpha-B subunits have a 3:1 ratio, respectively.^[6]

Function

Alpha B chain crystallins (αBC) can be induced by heat shock, ischemia, and oxidation, and are members of the small heat shock protein (sHSP also known as the HSP20) family.^[6][13] They act as molecular chaperones although they do not renature proteins and release them in the fashion of a true chaperone; instead, they bind improperly folded proteins to prevent protein aggregation.^[6][7][8]

Furthermore, αBC may confer stress resistance to cells by inhibiting the processing of the pro-apoptotic protein caspase-3.^[8] Two additional functions of alpha crystallins are an autokinase activity and participation in the intracellular architecture. Alpha-A and alpha-B gene products are differentially expressed; alpha-A is preferentially restricted to the lens and alpha-B is expressed widely in many tissues and organs. Elevated expression of alpha-B crystallin occurs in many neurological diseases; a missense mutation cosegregated in a family with a desmin-related myopathy.^[6]

Clinical significance

Although not yet clearly understood, defective chaperone activity is expected to trigger the accumulation of protein aggregates and underlie the development of α-crystallinopathy, or the failure of protein quality control, resulting in protein deposition diseases such as Alzheimer’s disease and Parkinson’s disease. Mutations in CRYAB could also cause restrictive cardiomyopathy.^[14] ER-anchored αBC can suppress aggregate formation mediated by the disease mutant. Thus, modulation of the micromilieu surrounding the ER membrane can serve as a potential target in developing pharmacological interventions for protein deposition disease.^[7]

Though expressed highly in eye lens and muscle tissues, αBC can also be found in several types of cancer, among which head and neck squamous cell carcinoma (HNSCC) and breast carcinomas, as well as in patients with tuberous sclerosis.^[15] αBC expression is associated with metastasis formation in HNSCC and in breast carcinomas and in other types of cancer, expression is often correlated with poor prognosis as well.^[16] The expression of αBC can be increased during various stresses, like heat shock, osmotic stress or exposure to heavy metals, which then may lead to prolonged survival of cells under these conditions.^[8]

Interactions

CRYAB has been shown to interact with:

• CRYAA,^[17]
• CRYBB2,^[17]
• CRYGC,^[17]
• HSPB2,^[18]
• Hsp27,^[17][19] and
• PSMA3.^[20]

References

Further reading

External links

• GeneReviews/NIH/NCBI/UW entry on Myofibrillar Myopathy