Person:
An, Heeseon

Profile Picture

Email Address

AA Acceptance Date

Birth Date

Research Projects

Organizational Units

Job Title

Last Name

An

First Name

Heeseon

Name

An, Heeseon

Filters

2017 - 20182

Settings

Author's Publications: search.filters.isAuthorOfPublication.c2cdf5c3-9819-4bd6-be33-06af8cce67d0

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    Publication
    Systematic Analysis of Ribophagy in Human Cells Reveals By-stander Flux During Selective Autophagy
    (2017) An, Heeseon; Harper, J. Wade
    Ribosomes are abundant cellular machines1,2 regulated by assembly, supernumerary subunit turnover, and nascent chain quality control mechanisms1–5. Moreover, nitrogen starvation in yeast has been reported to promote selective ribosome delivery to the vacuole in an autophagy conjugation system-dependent manner, a process called “ribophagy”6,7. However, whether ribophagy in mammals is selective or regulated is unclear. Using Ribo-Keima flux reporters, we find that starvation or mTOR inhibition promotes VPS34-dependent ribophagic flux, which unlike yeast, is largely ATG8 conjugation independent and occurs concomitantly with other cytosolic protein autophagic flux reporters8,9. Ribophagic flux was not induced upon inhibition of translational elongation or nascent chain uncoupling, but was induced in a comparatively selective manner upon proteotoxic stress via arsenite10 or chromosome mis-segregation11 dependent upon VPS34 and ATG8 conjugation. Unexpectedly, agents typically used to induce selective autophagy also promoted increased ribosome and cytosolic protein reporter flux, suggesting significant bulk or “by-stander” autophagy during what is often considered selective autophagy12,13. These results emphasize the importance of monitoring non-specific cargo flux when assessing selective autophagy pathways.
  • Thumbnail Image
    Publication
    Dynamic recruitment of ubiquitin to mutant huntingtin inclusion bodies
    (Nature Publishing Group UK, 2018) Juenemann, Katrin; Jansen, Anne H. P.; van Riel, Luigi; Merkx, Remco; Mulder, Monique P. C.; An, Heeseon; Statsyuk, Alexander; Kirstein, Janine; Ovaa, Huib; Reits, Eric A.
    Many neurodegenerative diseases, such as Huntington’s disease, are hallmarked by the formation of intracellular inclusion bodies (IBs) that are decorated with ubiquitin, proteasomes and chaperones. The apparent enrichment of ubiquitin and components involved in protein quality control at IBs suggests local ubiquitin-dependent enzymatic activity. In this study, we examine recruitment of ubiquitin to IBs of polyglutamine-expanded huntingtin fragments (mHtt) by using synthesized TAMRA-labeled ubiquitin moieties. We show that intracellular TAMRA-ubiquitin is dynamic at mHtt IBs and is incorporated into poly-ubiquitin chains of intracellular substrates, such as mHtt, in a conjugation-dependent manner. Furthermore, we report that mHtt IBs recruit catalytically active enzymes involved in (de)-ubiquitination processes based on novel activity-based probes. However, we also find that the overexpression of the GFP-ubiquitin reporter, unlike the endogenous ubiquitin and TAMRA-ubiquitin, becomes irreversibly sequestered as a ring-like structure around the mHtt IBs, suggesting a methodical disadvantage of GFP-tagged ubiquitin. Our data provide supportive evidence for dynamic recruitment of ubiquitin and ubiquitin (de)-conjugating activity at mHtt initiated IBs.