Activated T cells transcribe an alternatively spliced mRNA encoding a soluble form of Qa-2 antigen.
Among the best characterized non-classical mouse major histocompatibility antigens are the Qa-2 molecules. These proteins can serve as targets for allogenic cytotoxic T cells and as signal transducing molecules. They are structurally similar to H-2 transplantation antigens in their N-terminal and beta 2-microglobulin binding domains but differ at their C-termini. While the H-2 antigens span the cell membrane, the Qa-2 molecules are attached to the cell surface via phospholipid anchors. The genetic information encoding this attachment is contained in exon 5. In concanavalin A activated splenocytes the expression of membrane bound Qa-2 antigens declines and, simultaneously, soluble forms of Qa-2 molecules are secreted. We demonstrate here that the soluble Qa-2 polypeptides are translated from alternatively spliced mRNAs lacking exon 5, while the membrane forms are encoded by the full-size transcripts. In cultured cells the alternative splicing of the Qa-2 message is induced by T-cell activation splicing of the Qa-2 message is induced by T-cell activation with concanavalin A. The canonical mRNA encoding the membrane form of Qa-2 predominates in unstimulated mouse tissues but the cultured cell lines, like activated T cells, express enhanced levels of the truncated mRNA. In some cell lines almost all Qa-2 transcripts lack exon 5. For example, in L cells, mRNAs encoding soluble Qa-2 molecules are at least 10 times more abundant than Qa-2 transcripts encoding phospholipid anchored antigens. These findings are discussed in terms of potential functions of membrane bound and secreted Qa-2 molecules.
Ulker
N
N
California Institute of Technology, Division of Biology, Pasadena 91125.
Lewis
K D
KD
Hood
L E
LE
Stroynowski
I
I
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D003001:Cloning, Molecular; D005091:Exons; D006031:Glycosylation; D006183:H-2 Antigens / Q000235:genetics; D015395:Histocompatibility Antigens Class I / Q000235:genetics*; D007739:L Cells / Q000276:immunology; D008213:Lymphocyte Activation; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D015345:Oligonucleotide Probes; D016133:Polymerase Chain Reaction; D012326:RNA Splicing; D012333:RNA, Messenger / Q000235:genetics*; D013601:T-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D014162:Transfection; D010738:Type C Phospholipases / Q000378:metabolism
D006183:H-2 Antigens; D015395:Histocompatibility Antigens Class I; D015345:Oligonucleotide Probes; C032907:Q surface antigens; D012333:RNA, Messenger; D010738:Type C Phospholipases