Identification and characterization of a novel surface antigen gene induced in mast cells activated through the high affinity IgE receptor.
In an effort to isolate novel genes involved in inflammation and/or mast cell activation, we have used a combination of differential screening and subtractive hybridization to isolate genes whose expression are induced upon activation of a transformed rat mast cell line. One of the isolated clones, pMCA-32, contained an open reading frame of 278 amino acids that included a putative hydrophobic transmembrane domain, a cysteine rich Ig-like extracellular domain, and a cytoplasmic domain containing three consensus SH2-domain phosphotyrosine binding sites. The MCA-32 gene is also highly conserved between rat and mouse, with the two coding regions being 73% identical. Although the MCA-32 coding region did not contain an obvious signal peptide, MCA-32 protein was detected on the surface of rat mast cells, and the cloned cDNA produced a cell surface protein when expressed in COS-7 cells. MCA-32 RNA from both mouse and rat undergoes alternative splicing, producing an mRNA containing an in-frame deletion of the TM domain, suggesting that a form of MCA-32 protein may be secreted. MCA-32 mRNA expression was up-regulated upon activation of RBL-2H3 cells and was highly abundant in primary peritoneal mast cells. Expression of MCA-32 RNA was only observed in primary and transformed mast cells from rat, while in the mouse MCA-32, RNA was also produced in significant amounts by a number of transformed monocyte cell lines. Thus, MCA-32 is a novel surface protein whose structure and expression suggest roles in the development and/or activation of mast cells and monocytes.
D000595:Amino Acid Sequence; D000818:Animals; D000954:Antigens, Surface / Q000235:genetics*; D001483:Base Sequence; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000032:analysis; D008407:Mast Cells / Q000737:chemistry*; D008565:Membrane Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017455:Receptors, IgE / Q000032:analysis / Q000502:physiology*; D014407:Tumor Cells, Cultured; D015854:Up-Regulation
D000954:Antigens, Surface; D018076:DNA, Complementary; D008565:Membrane Proteins; C097128:Milr1 protein, rat; D012333:RNA, Messenger; D017455:Receptors, IgE