Signal regulatory protein alpha (SIRPA, designated CD172a), also called SHPS-1 (SHP substrate 1) and previously, MyD-1 (Myeloid/Dendritic-1), is a monomeric ~90kD 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 SIRPA 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 SIRPA has more than 40 described polymorphisms, including the prominent BIT (Brain Ig-like molecule with Tyrosine-based activation motifs, also called SIRPA2 or PTPNS).5 One reported isoform lacks aa 1-101, which eliminates most of the V-type Ig domain. Human SIRPA ECD shares 61%, 60%, 71%, 72% and 73% aa identity with mouse, rat, porcine, bovine and equine SIRPA, respectively; it shares 84% and 76% aa identity with human SIRPB1 and SIRPy, respectively.2 SIRPA 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 SIRPA shows adhesion to the ubiquitous CD47/IAP (integrin-associated protein), while SIRPY binds more weakly and SIRPA1 does not bind at all.1, 2 Mouse and human SIRPA-CD47 binding only cross-reacts for specific polymorphisms and influences engraftment of xenotransplanted stem cells.6, 10 SIRPA engagement generally produces a negative regulatory signal.4 Low SIRPA recognition of CD47, which occurs on aged erythrocytes or platelets or xenogenic cells, promotes clearance of CD47low cells from circulation.11-13 SIRPA Arecognition of surfactants SP-A and SP-D in the lung can inhibit alveolar macrophage cytokine production.14 CD47- integrin-SIRPA interaction is reported to promote macrophage fusion during osteoclastogenesis.15
A DNA sequence encoding the extracellular domain of human SIRPa (Gly 27-Arg 370 & Glu31-Arg370; Accession # NP_542970) was fused to the Fc region of human IgG1 (Pro100-Lys330) via a polypeptide linker. The chimeric protein was expressed in Chinese hamster ovary cells.
Calculated molecular mass of ~ 64kD. As a result of glycosylation, the recombinant protein migrates as an ~ 70-105kD protein in SDS-PAGE under reducing conditions.
Activity:Measured by the ability of the immobilized protein to support the adhesion of red blood cells (Subramanian S., et al., 2006, Blood 107:2548-2556). Red blood cells added at 10x10e6 cells/ml (100ul/well) to SIRPa coated plated will adhere after 1hour at 37ºC. The ED50 for this effect is 0.6-2.4ug/ml.
Storage and Stability:Lyophilized powder may be stored at -20°C. Stable for 12 months after receipt at -20°C. Reconstitute with sterile PBS. Aliquot to avoid repeated freezing and thawing. Store at -20°C. Reconstituted product is stable for 6 months at -20°C. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap. Further dilutions can be made in assay buffer.
仕様
Size：50ug
Source Antigen：Recombinant, CHO cells
Grade：Purified
Purity：≥90%, as determined by SDS-PAGE under reducing conditions and visualized by silver stain. Endotoxin: ≤1EU/1ug.
Form：Supplied as a lyophilized powder from PBS, pH 7.4. Reconstitute with 500ul sterile PBS.
