title: Presenilin/gamma-secretase and alpha-secretase-like peptidases cleave human MHC Class I proteins.
abstract: HLA (human leucocyte antigen)-A2 is an MHC Class I protein with primary functions in T-cell development and initi-ation of immune cell responses. MHC I proteins also play roles in intercellular adhesion, apoptosis, cell proliferation and neuronal plasticity. By utilizing a sequence comparison analysis, we recently identified HLA-A2 as a potential substrate for the Alzheimer's disease-associated PS1 (presenilin 1)/gamma-secretase. alpha-Secretase-like membrane metalloproteinases are responsible for an initial shedding event, partially mediated by ADAM (a disinteg-rin and metalloproteinase)-10. Accordingly, activation or inhibition of alpha-secretase-like membrane metalloproteinases directly modulated levels of a 14 kDa HLA-A2 CTF (C-terminal frag-ment) in CHO (Chinese-hamster ovary) cells. To show that the HLA-A2 CTF is subsequently cleaved by PS1/gamma-secretase, we re-duced its activity in cell lines stably expressing HLA-A2 and in Jurkat T-cells expressing endogenous MHC I. Treatment with specific PS1/gamma-secretase inhibitors or expression of a dominant-negative construct led to a significant accumulation of HLA-A2 CTFs. We also identified the PS1/gamma-secretase cleavage product of HLA-A2 CTF, termed HLA-A2 intracellular domain, in cell-free and cell-based experiments. In the absence of proteasome inhibitors, HLA-A2 intracellular domain underwent rapid degrad-ation. These data indicate that MHC I proteins undergo extra-cellular domain cleavage mediated by alpha-secretases and the cleavage product is subsequently cleaved by PS1/gamma-secretase.
authors.affiliation: Neurobiology of Disease Laboratory, Genetics and Aging Research Unit/MIND, Department of Neurology, Massachusetts General Hospital, Harvard Medical School, 114 16th St., Charlestown, MA 02129, USA.
authors.forename: Bryce W
authors.initials: BW
authors.lastname: Carey
authors.forename: Doo Y
authors.initials: DY
authors.lastname: Kim
authors.forename: Dora M
authors.initials: DM
authors.lastname: Kovacs
mesh_terms: D053829:Amyloid Precursor Protein Secretases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D015789:HLA-A2 Antigen / Q000378:metabolism; D015395:Histocompatibility Antigens Class I / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D008285:Major Histocompatibility Complex; D053763:Presenilins / Q000378:metabolism*; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D013379:Substrate Specificity; D014162:Transfection
chemical_list: D015789:HLA-A2 Antigen; D015395:Histocompatibility Antigens Class I; D053763:Presenilins; D011994:Recombinant Proteins; D053829:Amyloid Precursor Protein Secretases