Objective: The aim of this study is to investigate the effect of mutant DNAJC13 on the vesicle transport machinery using cultured cellular model.

Background: Recently, a missense mutation (p.N855S) in DNAJC13 gene has been identified in patients with autosomal dominant, rare familial forms of Parkinson’s disease (PD). DNAJC13 has been known as a Dnaj-domain-containing protein that is tightly associated with endosomal membrane.

Methods: COS7 cells were transiently transfected with GFP-tagged DNAJC13 together with mStrawberry-tagged Rab GTPase constructs. The expression and subcellular localization of DNAJC13 were examined using laser scanning microscope (LSM) and Western blot analyses. To determine how the DNAJC13 mutant affects on the different endosomal pathway, cells over-expressing wt or mutant DNAJC13 were incubated in the culture media containing reference molecules including EGF and Alexa555-labeled transferrin. Time-lapse images of internalized reference molecules were acquired using LSM. To assess the subcellular distribution of α-synuclein in the presence of mutant DNAJC13, HEK293 cells expressing α-synuclein were co-transfected either with wt or mutant DNAJC13 under the existence of cycloheximide and subjected to subcellular fractionation analysis.

Results: While wt-DNAJC13 was exclusively co-localized with rab5A-positive endosome, N855S mutant was co-localized with not only rab5A but also Rab7 or Rab11A-positive endosome. The cargo-trafficking from early endosome to late endosome and/or recycling endosome was substantially impaired in cells over-expressing N855S DNAJC13. Moreover, endosomal retention of α-synuclein was observed in the cells expressing mutant DNAJC13.

Conclusions: PD-linked DNAJC13 mutation impairs endosomal cargo trafficking including α-synuclein and would thereby contribute to the pathogenesis of the disease.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/parkinsons-disease-linked-mutation-in-dnajc13-causes-specific-trafficking-defect-in-endosomal-pathway/