- Other Names
- Human SIRPa, SIRPα, SIRPA, SIRPalpha, CD172a, Brain Ig-like molecule with tyrosine-based activation motifs, BIT, Macrophage Fusion Receptor, MFR, P84, MYD-1, SHP substrate 1, SHPS1, Tyrosine-protein phosphatase non-receptor type substrate 1, PTPNS1
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Signal Regulatory Proteins (SIRPs) are a family of transmembrane glycoproteins with extracellular IgG domains. SIRPα is an inhibitory receptor expressed on neurons and myeloid cells, including macrophages, granulocytes, myeloid dendritic cells, mast cells, and their precursors (including hematopoietic stem cells). The extracellular regions of the SIRPs are comprised of three Ig-like loops; the proximal loops contain IgC domains, whereas the distal membrane loop contains an IgV domain. While these extracellular domains are fairly similar between SIRPs, their transmembrane and cytoplasmic domains differentiate them from one another. The C-terminal intracellular domains of the SIRPα subfamily contain a relatively long amino acid sequence that includes four tyrosine residues to form two immunoreceptor tyrosine-based inhibition motifs (ITIM). SIRPα is best known for its inhibitory role following its interaction with the widely distributed protein CD47 (on host target cells). CD47 is a “marker of self”, which upon binding to SIRPα signals against phagocytosis by macrophages expressing SIRPα. When CD47 binds the N-terminal IgG domain of SIRPα, this causes clustering and phosphorylation of SIRPα. SIRPα phosphorylation results in the recruitment and activation of the tyrosine phosphatases SHP-1 and SHP-2, which regulate cellular functions in a negative fashion, including the regulation of leukocyte adhesion and transmigration, T cell activation, macrophage fusion and phagocytosis. In addition to its role in "self-signaling", SIRPα also functions as a scaffold for membrane-bound signaling molecules, plays a role in macrophage and osteoclast fusion, regulates T cell/DC activation and controls myeloid cell migration.Product Details
- Human SIRPα, amino acid Gly27-Arg370 (Accession #P78324.2), with a C-terminal human IgG1 Fc tag, was expressed in CHO cells.
- Molecular Mass
- The 579 amino acid recombinant protein has a predicted molecular mass of approximately 63.9 kD. The DTT-reduced protein migrates at approximately 75 - 100 kD and and the non-reduced protein migrates at approximately 150 - 200 kD by SDS-PAGE. The predicted N-terminal amino acid is Gly.
- >95%, as determined by Coomassie stained SDS-PAGE.
- 0.22 µm filtered protein solution is in PBS, pH 7.2.
- Endotoxin Level
- Less than 0.01 ng per µg cytokine as determined by the LAL method.
- 10 and 25 µg sizes are bottled at 200 µg/mL. 100 µg and larger sizes are lot-specific and bottled at the concentration indicated on the vial (please contact technical support for concentration, or use our Lookup tool if you have a lot number).
- Storage & Handling
- Unopened vial can be stored between 2°C and 8°C for up to 2 weeks, at -20°C for up to six months, or at -70°C or colder until the expiration date. For maximum results, quick spin vial prior to opening. The protein can be aliquoted and stored at -20°C or colder. Stock solutions can also be prepared at 50 - 100 µg/mL in appropriate sterile buffer, carrier protein such as 0.2 - 1% BSA or HSA can be added when preparing the stock solution. Aliquots can be stored between 2°C and 8°C for up to one week and stored at -20°C or colder for up to 3 months. Avoid repeated freeze/thaw cycles.
- ED50 = 0.15 - 0.6 µg/mL as measured by the ability of immobilized protein to support the adhesion of human red blood cells. When human SIRPα-Fc Chimera is coated at 2.0 µg/mL (100µL/well), human CD47 binds with an EC50 of 5 - 20 ng/mL.
- Application Notes
BioLegend carrier-free recombinant proteins provided in liquid format are shipped on blue ice. Our comparison testing data indicates that when handled and stored as recommended, the liquid format has equal or better stability and shelf-life compared to commercially available lyophilized proteins after reconstitution. Our liquid proteins are validated in-house to maintain activity after shipping on blue ice and are backed by our 100% satisfaction guarantee. If you have any concerns, contact us at firstname.lastname@example.org.
- Disulfide-linked homodimer
Broadly distributed in normal adult tissues including brain, endocrine tissues, bone marrow/immune system, lung, pancreas, gastrointestinal tract, kidney, testis, and ovary
- An inhibitory receptor present on myeloid cells that interacts with a widely distributed membrane protein CD47 to prevent phagocytosis of healthy cells.
- Interacts with CD47-expressing cells throughout the body.
- Measured by the ability of immobilized protein to induce the adhesion of human red blood cells. Also measured by its ability to bind CD47 in a functional ELISA.
- Cell Type
- Macrophages, Neurons
- Biology Area
- Cell Adhesion, Innate Immunity, Neuroscience
- Molecular Family
- Adhesion Molecules, Soluble Receptors
- Antigen References
- van Beek EM, et al. 2005. J Immunol. 12:7781-7.
- Lee WY, et al. 2007. J Immunol. 11:7741–50.
- Subramanian S, et al. 2006. Blood 107: 2548-56.
- Barclay AN. 2009. Current Opinion in Immunology 21:47-52.
- Liu Y, et al. 2005. J Biol Chem. 43:36132-40.
- Gene ID
- 140885 View all products for this Gene ID
- View information about SIRPalpha on UniProt.org
- Does specific activity of a recombinant protein vary between lots?
Specific activity will vary for each lot and for the type of experiment that is done to validate it, but all passed lots will have activity within the established ED50 range for the product and we guarantee that our products will have lot-to-lot consistency. Please conduct an experiment-specific validation to find the optimal ED50 for your system.
- Have your recombinants been tested for stability?
Our testing shows that the recombinant proteins are able to withstand room temperature for a week without losing activity. In addition the recombinant proteins were also found to withstand four cycles of freeze and thaw without losing activity.
- How do you convert activity as an ED50 in ng/ml to a specific activity in Units/mg?
- Use formula Specific activity (Units/mg) = 10e6/ ED50 (ng/mL)
- How does the activity of your recombinant proteins compare to competitors?
We quality control each and every lot of recombinant protein. Not only do we check its bioactivity, but we also compare it against other commercially available recombinant proteins. We make sure each recombinant protein’s activity is at least as good as or better than the competition’s. In order to provide you with the best possible product, we ensure that our testing process is rigorous and thorough. If you’re curious and eager to make the switch to BioLegend recombinants, contact your sales representative today!
- What is the specific activity or ED50 of my recombinant protein?
The specific activity range of the protein is indicated on the product datasheets. Because the exact activity values on a per unit basis can largely fluctuate depending on a number of factors, including the nature of the assay, cell density, age of cells/passage number, culture media used, and end user technique, the specific activity is best defined as a range and we guarantee the specific activity of all our lots will be within the range indicated on the datasheet. Please note this only applies to recombinants labeled for use in bioassays. ELISA standard recombinant proteins are not recommended for bioassay usage as they are not tested for these applications.