Detection of SPARC in Human HT1080 Cell Line byFlow Cytometry.
HT1080 human fibrosarcoma cell line wasstained with Mouse Anti-Human SPARC Alexa Fluor® 647-conjugated MonoclonalAntibody (Catalog # IC941R, filled histogram) or isotype control antibody(Catalog # IC002R, open histogram). To facilitate intracellular staining,cells were fixed with Flow Cytometry Fixation Buffer (Catalog # FC004)and permeabilized with Flow Cytometry Permeabilization/Wash Buffer I(Catalog # FC005). View our protocol for Staining Intracellular Molecules.
Preparation and Storage
The product is shipped with polar packs. Upon receipt, store it immediately at the temperature recommended below.
Stability & Storage
Protect from light. Do not freeze.
12 months from date of receipt, 2 to 8 °C as supplied.
SPARC, an acronym for “secreted protein, acidic and rich in cysteine”, is also known as osteonectin or BM-40 (1-5). It is the founding member of a family of secreted matricellular proteins with similar domain structure. The 286 amino acid (aa), 43 kDa protein contains an N-terminal acidic region that binds calcium, a follistatin domain that contains Kazal-like sequences, and a C-terminal extracellular calcium (EC) binding domain with two EF-hand motifs (1-5). Crystal structure modeling shows that residues implicated in cell binding, inhibition of cell spreading, and disassembly of focal adhesions cluster on one face of SPARC, while a collagen binding epitope and an N-glycosylation site are opposite this face (6). SPARC is produced by fibroblasts, capillary endothelial cells, platelets and macrophages, especially in areas of tissue morphogenesis and remodeling (3, 7). SPARC shows context-specific effects, but generally inhibits adhesion, spreading and proliferation, and promotes collagen matrix formation (3-5). For endothelial cells, SPARC disrupts focal adhesions and binds and sequesters PDGF and VEGF (3-5). SPARC is abundantly expressed in bone, where it promotes osteoblast differentiation and inhibits adipogenesis (5, 8). SPARC is potentially cleaved by metalloproteinases, producing an angiogenic peptide that includes the copper-binding sequence KGHK (7). Paradoxically, SPARC is highly expressed in many tumor types undergoing an endothelial to mesenchymal transition; its expression, however, mainly decreases the likelihood of metastasis and confers sensitivity to chemotherapy and radiation (4, 9-11). Stabilin-1, which is expressed on alternately activated macrophages, is the first SPARC receptor to be identified. It binds the SPARC EC domain and mediates endocytosis for degradation (12). Mature human SPARC shows 92%, 92%, 97%, 99%, 96% and 85% aa identity with mouse, rat, canine, bovine, porcine and chick SPARC, respectively.
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Secreted Protein Acidic and Rich in Cysteine
Entrez Gene IDs:
6678 (Human); 20692 (Mouse)
Basement-membrane protein 40; BM-40; ONcysteine-rich protein; Osteonectin; Secreted protein acidic and rich in cysteine; secreted protein, acidic, cysteine-rich (osteonectin); SPARC
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