title: Midline 1 directs lytic granule exocytosis and cytotoxicity of mouse killer T cells.
abstract: Midline 1 (MID1) is a microtubule-associated ubiquitin ligase that regulates protein phosphatase 2A activity. Loss-of-function mutations in MID1 lead to the X-linked Opitz G/BBB syndrome characterized by defective midline development during embryogenesis. Here, we show that MID1 is strongly upregulated in murine cytotoxic lymphocytes (CTLs), and that it controls TCR signaling, centrosome trafficking, and exocytosis of lytic granules. In accordance, we find that the killing capacity of MID1(-/-) CTLs is impaired. Transfection of MID1 into MID1(-/-) CTLs completely rescued lytic granule exocytosis, and vice versa, knockdown of MID1 inhibited exocytosis of lytic granules in WT CTLs, cementing a central role for MID1 in the regulation of granule exocytosis. Thus, MID1 orchestrates multiple events in CTL responses, adding a novel level of regulation to CTL activation and cytotoxicity.
authors.affiliation: Department of International Health, Immunology and Microbiology, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Lasse
authors.initials: L
authors.lastname: Boding
authors.forename: Ann K
authors.initials: AK
authors.lastname: Hansen
authors.forename: Germana
authors.initials: G
authors.lastname: Meroni
authors.forename: Bo B
authors.initials: BB
authors.lastname: Johansen
authors.forename: Thomas H
authors.initials: TH
authors.lastname: Braunstein
authors.forename: Charlotte M
authors.initials: CM
authors.lastname: Bonefeld
authors.forename: Martin
authors.initials: M
authors.lastname: Kongsbak
authors.forename: Benjamin A H
authors.initials: BA
authors.lastname: Jensen
authors.forename: Anders
authors.initials: A
authors.lastname: Woetmann
authors.forename: Allan R
authors.initials: AR
authors.lastname: Thomsen
authors.forename: Niels
authors.initials: N
authors.lastname: Odum
authors.forename: Marina R
authors.initials: MR
authors.lastname: von Essen
authors.forename: Carsten
authors.initials: C
authors.lastname: Geisler
mesh_terms: D000818:Animals; D015153:Blotting, Western; D003602:Cytotoxicity, Immunologic / Q000276:immunology*; D005089:Exocytosis / Q000502:physiology*; D005434:Flow Cytometry; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D011506:Proteins / Q000276:immunology* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D022142:Secretory Vesicles / Q000276:immunology / Q000378:metabolism*; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology* / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases
chemical_list: D011506:Proteins; C109037:Mid1 protein, mouse; D044767:Ubiquitin-Protein Ligases
keywords: Cytotoxicity; Granule exocytosis; Midline 1; T cells