S100 calcium-binding protein B (S100B) is a protein of the S100 protein family.

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S100B
Available structures PDB Ortholog search: PDBe RCSB List of PDB id codes 1MQ1, 1UWO, 2H61, 2M49, 2PRU, 3CZT, 3D0Y, 3D10, 3HCM, 4XYN, 5CSJ, 5CSF, 5CSN, 5CSI
Identifiers
Aliases	S100B, NEF, S100, S100-B, S100beta, S100 calcium binding protein B
External IDs	OMIM: 176990 MGI: 98217 HomoloGene: 4567 GeneCards: S100B
Gene location (Human) Chr. Chromosome 21 (human)[1] Band 21q22.3 Start 46,598,604 bp[1] End 46,605,208 bp[1]
Gene location (Mouse) Chr. Chromosome 10 (mouse)[2] Band 10 C1|10 38.76 cM Start 76,089,687 bp[2] End 76,096,993 bp[2]
RNA expression pattern Bgee Human Mouse (ortholog) Top expressed in inferior ganglion of vagus nerve olfactory bulb subthalamic nucleus trigeminal ganglion internal globus pallidus medulla oblongata superior vestibular nucleus substantia nigra pons optic nerve Top expressed in anterior horn of spinal cord cerebellar vermis stria vascularis pontine nuclei facial motor nucleus optic nerve utricle dorsal tegmental nucleus medial vestibular nucleus ventral tegmental area More reference expression data BioGPS More reference expression data
Gene ontology Molecular function calcium ion binding S100 protein binding protein homodimerization activity zinc ion binding metal ion binding calcium-dependent protein binding protein binding identical protein binding tau protein binding signaling receptor binding RAGE receptor binding Cellular component cytoplasm ruffle extracellular region neuronal cell body perinuclear region of cytoplasm nucleus extracellular space Biological process axonogenesis response to glucocorticoid memory negative regulation of skeletal muscle cell differentiation central nervous system development astrocyte differentiation positive regulation of synaptic transmission positive regulation of cell population proliferation regulation of cell shape positive regulation of apoptotic process learning or memory positive regulation of I-kappaB kinase/NF-kappaB signaling regulation of neuronal synaptic plasticity response to methylmercury cell population proliferation innate immune response cellular response to hypoxia long-term potentiation positive regulation of myelination Sources:Amigo / QuickGO
Orthologs Species Human Mouse Entrez 6285 20203 Ensembl ENSG00000160307 ENSMUSG00000033208 UniProt P04271 P50114 RefSeq (mRNA) NM_006272 NM_009115 RefSeq (protein) NP_006263 NP_033141 Location (UCSC) Chr 21: 46.6 – 46.61 Mb Chr 10: 76.09 – 76.1 Mb PubMed search [3] [4]
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S100 proteins are localized in the cytoplasm and nucleus of a wide range of cells, and involved in the regulation of a number of cellular processes such as cell cycle progression and differentiation. S100 genes include at least 13 members which are located as a cluster on chromosome 1q21; however, this gene is located at 21q22.3.

S100B is glial-specific and is expressed primarily by astrocytes, but not all astrocytes express S100B. It has been shown that S100B is only expressed by a subtype of mature astrocytes that ensheath blood vessels and by NG2-expressing cells.^[5]

This protein may function in neurite extension, proliferation of melanoma cells, stimulation of Ca²⁺ fluxes, inhibition of PKC-mediated phosphorylation, astrocytosis and axonal proliferation, and inhibition of microtubule assembly. In the developing CNS it acts as a neurotrophic factor and neuronal survival protein. In the adult organism it is usually elevated due to nervous system damage, which makes it a potential clinical marker.

Chromosomal rearrangements and altered expression of this gene have been implicated in several neurological, neoplastic, and other types of diseases, including Alzheimer disease, Down syndrome, epilepsy, amyotrophic lateral sclerosis, schwannoma, melanoma, and type I diabetes mellitus.^[6]

It has been suggested that the regulation of S100B by melittin has potential for the treatment of epilepsy.^[7]

S100B is secreted by astrocytes or can spill from injured cells and enter the extracellular space or bloodstream. Serum levels of S100B increase in patients during the acute phase of brain damage. Over the last decade, S100B has emerged as a candidate peripheral biomarker of blood–brain barrier (BBB) permeability and CNS injury. Elevated S100B levels accurately reflect the presence of neuropathological conditions including traumatic head injury or neurodegenerative diseases. Normal S100B levels reliably exclude major CNS pathology. Its potential clinical use in the therapeutic decision making process is substantiated by a vast body of literature (citation?) validating variations in serum 100B levels with standard modalities for prognosticating the extent of CNS damage: alterations in neuroimaging, cerebrospinal pressure, and other brain molecular markers (neuron specific enolase and glial fibrillary acidic protein). However, more importantly, S100B levels have been reported to rise prior to any detectable changes in intracerebral pressure, neuroimaging, and neurological examination findings. Thus, the major advantage of using S100B is that elevations in serum or CSF levels provide a sensitive measure for determining CNS injury at the molecular level before gross changes develop, enabling timely delivery of crucial medical intervention before irreversible damage occurs. S100B serum levels are elevated before seizures suggesting that BBB leakage may be an early event in seizure development. ^[8] An extremely important application of serum S100B testing is in the selection of patients with minor head injury who do not need further neuroradiological evaluation, as studies comparing CT scans and S100B levels have demonstrated S100B values below 0.12 ng/mL are associated with low risk of obvious neuroradiological changes (such as intracranial hemorrhage or brain swelling) or significant clinical sequelae.^[9] The excellent negative predictive value of S100B in several neurological conditions is due to the fact that serum S100B levels reflect blood–brain barrier permeability changes even in absence of neuronal injury.^[10][11] In addition, S100B, which is also present in human melanocytes, is a reliable marker for melanoma malignancy both in bioptic tissue and in serum.^[12][13]

S100B has been shown to interact with:

• AHNAK,^[14]
• IMPA1,^[15]
• IQGAP1,^[16]
• MAPT,^[17][18] and
• P53,^[19]
• PGM1,^[20]
• S100A1,^[21][22]
• S100A6,^[22][23]
• S100A11,^[23]
• VAV1.^[24]