Recombinant Human SIRP alpha Fc Biotinylated Protein, CF Summary
Optimal dilutions should be determined by each laboratory for each application.
|Human SIRP alpha |
Accession # NP_542970
CF stands for Carrier Free (CF). We typically add Bovine Serum Albumin (BSA) as a carrier protein to our recombinant proteins. Adding a carrier protein enhances protein stability, increases shelf-life, and allows the recombinant protein to be stored at a more dilute concentration. The carrier free version does not contain BSA.
In general, we advise purchasing the recombinant protein with BSA for use in cell or tissue culture, or as an ELISA standard. In contrast, the carrier free protein is recommended for applications, in which the presence of BSA could interfere.
|Formulation||Lyophilized from a 0.2 μm filtered solution in PBS.|
|Reconstitution||Reconstitute at 500 μg/mL in PBS.|
|Shipping||The product is shipped with polar packs. Upon receipt, store it immediately at the temperature recommended below.|
|Stability & Storage:||Use a manual defrost freezer and avoid repeated freeze-thaw cycles.
Both immobilized unlabeled Recombinant Human SIRP alpha /CD172a Fc Chimera (Catalog # 4546-SA) and Biotinylated Recombinant Human SIRP alpha/CD172a Fc Chimera (Catalog # BT4546) support the adhesion of human red blood cells. The ED50 for this effect is 0.6-2.4 μg/mL. The similarity in activity highlights that the biotinylated protein is fully functional.
Background: SIRP alpha/CD172a
Signal regulatory protein alpha (SIRP alpha, designated CD172a), also called SHPS-1 (SHP substrate 1) and previously, MyD-1 (Myeloid/Dendritic-1), is a monomeric ~90 kDa type I transmembrane glycoprotein that belongs to the SIRP/SHPS (CD172) family of the immunoglobulin superfamily (1-4). SIRPs are paired receptors, with similar extracellular domains but differing C-termini and functions (1, 2). The 503 amino acid (aa) human SIRP alpha contains a 342 aa extracellular domain (ECD), with one V-type, and two C1 type Ig domains, and three potential N glycosylation sites. It has a 110 aa cytoplasmic sequence with ITIM motifs that recruit tyrosine phosphatases SHP-1 and SHP-2 when phosphorylated (4). Human SIRP alpha has more than 40 described polymorphisms, including the prominent BIT (Brain Ig like molecule with Tyrosine-based activation motifs, also called SIRP alpha 2 or PTPNS) (5). One reported isoform lacks aa 1-101, which eliminates most of the V type Ig domain. Human SIRP alpha ECD shares 61%, 60%, 71%, 72% and 73% aa identity with mouse, rat, porcine, bovine and equine SIRP alpha, respectively; it shares 84% and 76% aa identity with human SIRP beta 1 and SIRP gamma, respectively (2). SIRP alpha is expressed mainly on myeloid cells, including macrophages, neutrophils, dendritic and Langerhans cells (3-6). It is also found on neurons, smooth muscle and endothelial cells (7-9). SIRP alpha shows adhesion to the ubiquitous CD47/IAP (integrin associated protein), while SIRP gamma binds more weakly and SIRP alpha 1 does not bind at all (1, 2). Mouse and human SIRP alpha -CD47 binding only cross-reacts for specific polymorphisms and influences engraftment of xenotransplanted stem cells (6, 10). SIRP alpha engagement generally produces a negative regulatory signal (4). Low SIRP alpha recognition of CD47, which occurs on aged erythrocytes or platelets or xenogenic cells, promotes clearance of CD47low cells from circulation (11, 13). SIRP alpha recognition of surfactants SP-A and SP-D in the lung can inhibit alveolar macrophage cytokine production (14). The CD47 integrin-SIRP alpha interaction is reported to promote macrophage fusion during osteoclastogenesis (15).
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- Swissprot Accession # P78324.
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- Takenaka, K. et al. (2007) Nat. Immunol. 8:1313.
- Ishikawa-Sekigami, T. et al. (2006) Biochem. Biophys. Res. Commun. 343:1197.
- Olsson, M. et al. (2005) Blood 105:3577.
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- Lundberg, P. et al. (2007) Biochem. Biophys. Res. Commun. 352:444.
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