• Purity

  >95%, by SDS-PAGE under reducing conditions and visualized by silver stain

• Endotoxin Level

  <0.10 EU per 1 μg of the protein by the LAL method.  

• Activity

  Measured by its ability to bind human IgG with an estimated K    _D <60 nM.  

• Source

  Mouse myeloma cell line, NS0-derived Ala17-Asn303, with a C-terminal 6-His tag

• Accession #

• N-terminal Sequence    
  Analysis

  Ala17

• Predicted Molecular Mass

  32 kDa

• SDS-PAGE

  38-45 kDa, reducing conditions

Background: FCRL1/FcRH1

Fc Receptor-Like 1 (FCRL1), also known as FcRH1, and IRTA5, is an approximately 50 kDa protein with sequence homology to classical Fc receptors. The type 1 transmembrane FCRL proteins contain from three to nine immunoglobulin-like domains. They are differentially expressed within the B cell lineage and can either promote or inhibit B cell proliferation and activation (1, 2). According to R&D Systems testing, FCRL1 binds to purified human IgG. Mature human FCRL1 consists of a 291 amino acid (aa) extracellular domain (ECD) with three Ig-like domains, a 21 aa transmembrane segment, and a 101 aa cytoplasmic domain with two immunotyrosine activation motifs (ITIMs) (3, 4). A charged glutamic acid within the transmembrane segment may mediate association with other signaling proteins. Alternative splicing may generate an isoform that lacks the transmembrane segment and an isoform that largely consists of the first two Ig-like domains (5).  Mouse FCRL1 contains only two Ig-like domains, but it shares 62% aa sequence identity with homologous regions of the human FCRL1 ECD. FCRL1 is expressed on pre-B cells and naive B cells (6, 7). It is downregulated upon B cell activation but upregulated on memory B cells (6, 8). FCRL1 is expressed on many B cell lymphoma and leukemia tumor cells with the exception of B cell acute lymphoblastic leukemia (9 - 11). Antibody crosslinking of FCRL1 triggers its tyrosine phosphorylation and augments B cell proliferation induced by the B cell receptor (6).

• References:

1. Davis, R.S. et al. (2007) Annu. Rev. Immunol. 25:525.

2. Maltais, L.J. et al. (2006) Nat. Immunol. 7:431.

3. Miller, I. et al. (2002) Blood 99:2662.

4. Davis, R.S. et al. (2001) Proc. Natl. Acad. Sci. 98:9772.

5. Accession # Q96LA6.

6. Leu, C.-M. et al. (2005) Blood 105:1121.

7. Li, F.J. et al. (2008) Blood 112:179.

8. Polson, A.G. et al. (2006) Int. Immunol. 18:1363.

9. Du, X. et al. (2008) Blood 111:338.

10. Kazemi, T. et al. (2008) Int. J. Cancer 123:2113.

11. Kazemi, T. et al. (2009) Cancer Immunol. Immunother. 58:989.

• Long Name:

  Fc Receptor-like 1

• Entrez Gene IDs:

  115350 (Human); 229499 (Mouse); 680665 (Rat)

• Alternate Names:

  BXMH1; CD307a antigen; CD307a; Fc receptor homolog 1; Fc receptor-like 1; FcRH1; FCRH1DKFZp667O1421; FCRL1; FcR-like protein 1; hIFGP1; IFGP family protein 1; IFGP1; IFGP1Fc receptor-like protein 1; Immune receptor translocation-associated protein 5; IRTA5; IRTA5immunoglobulin superfamily Fc receptor, gp42