title: Regulation of NKG2D-ligand cell surface expression by intracellular calcium after HDAC-inhibitor treatment.
abstract: In this study we demonstrate that histone deacetylase (HDAC)-inhibitor mediated cell surface expression of the structural different NKG2D-ligands MICA/B and ULBP2 is calcium-dependent. Treatment with the calcium chelator EGTA inhibited constitutive as well as HDAC-inhibitor induced MICA/B and ULBP2 cell surface expression on melanoma cells and Jurkat T-cells. A NKG2D-dependent cytolytic assay and staining with a recombinant NKG2D-Fc fusion protein showed that calcium chelation impaired the functional ability of NKG2D-ligands induced by HDAC-inhibitor treatment. The HDAC-inhibitor induced cell surface expression of ULBP2, but not MICA/B, was sensitive to treatment calmidazolium and trifluoperazine, two agents known to block calcium signaling. siRNA-mediated knock-down of the calcium-regulated proteins calmodulin or calpain did however not affect NKG2D-ligand cell surface expression on Jurkat T-cells. We further show that secretion and cell surface binding of the calcium-regulating protein galectin-1 is enhanced upon HDAC-inhibitor treatment of melanoma cells. However, binding of galectin-1 to cell surface glycoproteins was not critical for constitutive or HDAC-inhibitor induced MICA/B and ULBP2 cell surface expression. We provide evidence that MICA/B and ULBP2 cell surface expression is controlled differently by calcium, which adds to the increasing perception that cell surface expression of MICA/B and ULBP2 is controlled by distinct signal transduction pathways.
authors.affiliation: Laboratory of Immunology, Section of Biomedicine, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark. hellejensen@fastmail.fm
authors.forename: Helle
authors.initials: H
authors.lastname: Jensen
authors.forename: Michael
authors.initials: M
authors.lastname: Hagemann-Jensen
authors.forename: Felicia
authors.initials: F
authors.lastname: Lauridsen
authors.forename: Søren
authors.initials: S
authors.lastname: Skov
mesh_terms: D001483:Base Sequence; D020013:Calcium Signaling / Q000187:drug effects; D002147:Calmodulin / Q000037:antagonists & inhibitors / Q000235:genetics; D002154:Calpain / Q000037:antagonists & inhibitors / Q000235:genetics; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D047630:Depsipeptides / Q000494:pharmacology; D058851:GPI-Linked Proteins / Q000378:metabolism; D037483:Galectin 1 / Q000378:metabolism; D055785:Gene Knockdown Techniques; D056572:Histone Deacetylase Inhibitors / Q000494:pharmacology*; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism*; D019169:Jurkat Cells; D008024:Ligands; D008545:Melanoma / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D014268:Trifluoperazine / Q000494:pharmacology
chemical_list: D002147:Calmodulin; D047630:Depsipeptides; D058851:GPI-Linked Proteins; D037483:Galectin 1; D056572:Histone Deacetylase Inhibitors; D007093:Imidazoles; D036341:Intercellular Signaling Peptides and Proteins; C445499:LGALS1 protein, human; D008024:Ligands; D034741:RNA, Small Interfering; C423230:ULBP2 protein, human; C423229:ULBP3 protein, human; D014268:Trifluoperazine; C031938:calmidazolium; C087123:romidepsin; D002154:Calpain