title: Open conformers: the hidden face of MHC-I molecules.
abstract: A pool of MHC-I molecules present at the plasma membrane can dissociate from the peptide and/or the light chain, becoming open MHC-I conformers. Whereas peptide-bound MHC-I molecules have an important role in regulating adaptive and innate immune responses, through trans-interactions with T cell and NK cell receptors, the function of the open MHC-I conformers is less clear but seems to be related to their inherent ability to cis-associate, both with themselves and with other receptors. Here, we review data indicating the open MHC-I conformers as regulators of ligand-receptor interactions and discuss the biological implications for immune and non-immune cells. The likelihood that the MHC-I heavy chains have hidden functions that are determined by the amino acid sequence of the alpha1 and alpha2 domains are discussed.
authors.affiliation: Lymphocyte Biology Group, Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, 4150-180 Porto, Portugal. farosa@ibmc.up.pt
authors.forename: Fernando A
authors.initials: FA
authors.lastname: Arosa
authors.forename: Susana G
authors.initials: SG
authors.lastname: Santos
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Powis
mesh_terms: D000818:Animals; D019281:Dimerization; D015395:Histocompatibility Antigens Class I / Q000737:chemistry* / Q000502:physiology; D006801:Humans; D011487:Protein Conformation
chemical_list: D015395:Histocompatibility Antigens Class I