S100 calcium-binding protein B (S100B) is a protein of the S100 protein family.
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.
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 injuryorneurodegenerative 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.
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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]
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^ abYang Q, O'Hanlon D, Heizmann CW, Marks A (February 1999). "Demonstration of heterodimer formation between S100B and S100A6 in the yeast two-hybrid system and human melanoma". Exp. Cell Res. 246 (2): 501–9. doi:10.1006/excr.1998.4314. PMID9925766.
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Duncan AM, Higgins J, Dunn RJ, Allore R, Marks A (1989). "Refined sublocalization of the human gene encoding the beta subunit of the S100 protein (S100B) and confirmation of a subtle t(9;21) translocation using in situ hybridization". Cytogenet. Cell Genet. 50 (4): 234–5. doi:10.1159/000132767. PMID2530061.
Allore R, O'Hanlon D, Price R, Neilson K, Willard HF, Cox DR, Marks A, Dunn RJ (1988). "Gene encoding the beta subunit of S100 protein is on chromosome 21: implications for Down syndrome". Science. 239 (4845): 1311–3. Bibcode:1988Sci...239.1311A. doi:10.1126/science.2964086. PMID2964086.
Jensen R, Marshak DR, Anderson C, Lukas TJ, Watterson DM (1985). "Characterization of human brain S100 protein fraction: amino acid sequence of S100 beta". J. Neurochem. 45 (3): 700–5. doi:10.1111/j.1471-4159.1985.tb04048.x. PMID4031854. S2CID46028228.
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Schäfer BW, Wicki R, Engelkamp D, Mattei MG, Heizmann CW (1995). "Isolation of a YAC clone covering a cluster of nine S100 genes on human chromosome 1q21: rationale for a new nomenclature of the S100 calcium-binding protein family". Genomics. 25 (3): 638–43. doi:10.1016/0888-7543(95)80005-7. PMID7759097.
1b4c: SOLUTION STRUCTURE OF RAT APO-S100B USING DIPOLAR COUPLINGS
1cfp: S100B (S100BETA) NMR DATA WAS COLLECTED FROM A SAMPLE OF CALCIUM FREE PROTEIN AT PH 6.3 AND A TEMPERATURE OF 311 K AND 1.7-6.9 MM CONCENTRATION, 25 STRUCTURES
1dt7: SOLUTION STRUCTURE OF THE C-TERMINAL NEGATIVE REGULATORY DOMAIN OF P53 IN A COMPLEX WITH CA2+-BOUND S100B(BB)
1mho: THE 2.0 A STRUCTURE OF HOLO S100B FROM BOVINE BRAIN
1mq1: Ca2+-S100B-TRTK-12 complex
1mwn: Solution NMR structure of S100B bound to the high-affinity target peptide TRTK-12
1psb: Solution structure of calcium loaded S100B complexed to a peptide from N-Terminal regulatory domain of NDR kinase.
1qlk: SOLUTION STRUCTURE OF CA(2+)-LOADED RAT S100B (BETABETA) NMR, 20 STRUCTURES
1sym: 3-D SOLUTION STRUCTURE OF REDUCED APO-S100B FROM RAT, NMR, 20 STRUCTURES
1uwo: CALCIUM FORM OF HUMAN S100B, NMR, 20 STRUCTURES
1xyd: NMR Solution Structure of Rat Zinc-Calcium-S100B, 20 Structures
