title: The tumor-associated antigen EBAG9 negatively regulates the cytolytic capacity of mouse CD8+ T cells.
abstract: CTLs eliminate virus-infected and tumorigenic cells through exocytosis of cytotoxic agents from lytic granules. While insights into the intracellular mechanisms facilitating lytic granule release have been obtained through analysis of loss-of-function mutations in humans and mice, there is a paucity of information on negative regulators of secretory lysosome release at the molecular level. By generating and analyzing estrogen receptor-binding fragment-associated antigen 9-KO (Ebag9 KO) mice, we show here that loss of EBAG9 confers CTLs with enhanced cytolytic capacity in vitro and in vivo. Although loss of EBAG9 did not affect lymphocyte development, it led to an increase in CTL secretion of granzyme A, a marker of lytic granules. This resulted in increased cytotoxicity in vitro and an enhanced cytolytic primary and memory T cell response in vivo. We further found that EBAG9 interacts with the adaptor molecule gamma2-adaptin, suggesting EBAG9 is involved in endosomal-lysosomal biogenesis and membrane fusion. Indeed, granzyme B was sorted to secretory lysosomes more efficiently in EBAG9-deficient CTLs than it was in WT CTLs, a finding consistent with the observed enhanced kinetics of cathepsin D proteolytic processing. While EBAG9 deficiency did not disrupt the formation of the immunological synapse, lytic granules in Ebag9-/- CTLs were smaller than in WT CTLs. These data suggest that EBAG9 is a tunable inhibitor of CTL-mediated adaptive immune response functions.
authors.affiliation: Max-Delbrück-Center for Molecular Medicine, Berlin, Germany.
authors.forename: Constantin
authors.initials: C
authors.lastname: Rüder
authors.forename: Uta E
authors.initials: UE
authors.lastname: Höpken
authors.forename: Jana
authors.initials: J
authors.lastname: Wolf
authors.forename: Hans-Willi
authors.initials: HW
authors.lastname: Mittrücker
authors.forename: Boris
authors.initials: B
authors.lastname: Engels
authors.forename: Bettina
authors.initials: B
authors.lastname: Erdmann
authors.forename: Susanne
authors.initials: S
authors.lastname: Wollenzin
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Uckert
authors.forename: Bernd
authors.initials: B
authors.lastname: Dörken
authors.forename: Armin
authors.initials: A
authors.lastname: Rehm
mesh_terms: D000818:Animals; D000951:Antigens, Neoplasm / Q000502:physiology*; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D002352:Carrier Proteins / Q000502:physiology; D002402:Cathepsin D / Q000378:metabolism; D002478:Cells, Cultured; D003602:Cytotoxicity, Immunologic; D003713:Dendritic Cells / Q000502:physiology; D011992:Endosomes / Q000378:metabolism; D053804:Granzymes / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D037102:Lectins / Q000502:physiology; D051907:Lysosomal Membrane Proteins / Q000032:analysis; D008247:Lysosomes / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D011948:Receptors, Antigen, T-Cell / Q000502:physiology; D013569:Synapses / Q000502:physiology; D033921:Vesicular Transport Proteins / Q000502:physiology; D052118:Lysosomal-Associated Membrane Protein 1
chemical_list: D000951:Antigens, Neoplasm; D002352:Carrier Proteins; D002402:Cathepsin D; D053804:Granzymes; D047908:Intracellular Signaling Peptides and Proteins; D037102:Lectins; D051907:Lysosomal Membrane Proteins; D011948:Receptors, Antigen, T-Cell; D033921:Vesicular Transport Proteins; C513476:Bloc1s6 protein, mouse; C534295:EBAG9 protein, mouse; C052255:Lamp1 protein, mouse; D052118:Lysosomal-Associated Membrane Protein 1; C498451:Snapin protein, mouse; C533923:Ctsd protein, mouse