Functional characterization of the lysosomal membrane protein TMEM192 in mice

Research output: Contribution to journalResearch articleContributedpeer-review

Contributors

  • Thuy Linh Nguyen - , Kiel University (Author)
  • Janna Schneppenheim - , Kiel University (Author)
  • Sönke Rudnik - , Kiel University (Author)
  • Renate Lüllmann-Rauch - , Kiel University (Author)
  • Christian Bernreuther - , University of Hamburg (Author)
  • Irm Hermans-Borgmeyer - , University of Hamburg (Author)
  • Markus Glatzel - , University of Hamburg (Author)
  • Paul Saftig - , Kiel University (Author)
  • Bernd Schröder - , Institute of Physiological Chemistry, Kiel University (Author)

Abstract

The Transmembrane protein 192 (TMEM192) is a lysosomal/late endosomal protein initially discovered by organellar proteomics. TMEM192 exhibits four transmembrane segments with cytosolic N- and C-termini and forms homodimers. Devoid of significant homologies, the molecular function of TMEM192 is currently unknown. Upon TMEM192 knockdown in hepatoma cells, a dysregulation of autophagy and increased apoptosis were reported. Here, we aimed to define the physiological role of TMEM192 by analysing consequences of TMEM192 ablation in mice. Therefore, we compared the biochemical properties of murine TMEM192 to those of the human orthologue. We reveal lysosomal residence of murine TMEM192 and demonstrate ubiquitous tissue expression. In brain, TMEM192 expression was pronounced in the hippocampus but also present in the cortex and cerebellum, as analysed based on a lacZ reporter allele. Murine TMEM192 undergoes proteolytic processing in a tissuespecific manner. Thereby, a 17 kDa fragment is generated which was detected in most murine tissues except liver. TMEM192 processing occurs after lysosomal targeting by pH-dependent lysosomal proteases. TMEM192-/- murine embryonic fibroblasts (MEFs) exhibited a regular morphology of endo-/lysosomes and were capable of performing autophagy and lysosomal exocytosis. Histopathological, ultrastructural and biochemical analyses of all major tissues of TMEM192-/- mice demonstrated normal lysosomal functions without apparent lysosomal storage. Furthermore, the abundance of the major immune cells was comparable in TMEM192-/- and wild type mice. Based on this, we conclude that under basal conditions in vivo the loss of TMEM192 can be efficiently compensated by alternative pathways. Further studies will be required to decipher its molecular function.

Details

Original languageEnglish
Pages (from-to)43635-43652
Number of pages18
JournalOncotarget
Volume8
Issue number27
Publication statusPublished - 2017
Peer-reviewedYes

External IDs

PubMed 28504966

Keywords

ASJC Scopus subject areas

Keywords

  • Autophagy, Lysosomal membrane, Lysosome, Proteolytic processing, Transmembrane protein 192