Date of Award
Fall 2022
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Molecular Biophysics and Biochemistry
First Advisor
Schlieker, Christian
Abstract
Collapse of protein quality control (PQC) is a defining feature of numerous neurological diseases. Work described within this thesis argues that DYT1 dystonia, a neurological movement disorder of unclear etiology, arises due to a PQC defect. While it is clear that mutations in the AAA+ ATPase TorsinA cause this disease, it is not known why loss of this protein function causes DYT1 dystonia. In cells lacking Torsin function, nuclear pore complexes (NPCs) fail to be properly assembled. Instead, nuclear envelope (NE) herniations form that sequester abundant molecular chaperones. Ubiquitylated proteins, that in healthy cells are rapidly degraded, become sequestered with these chaperones. The protein MLF2, identified through proteomic approaches as enriched inside NE herniations, recruits DNAJB6 to these structures. Performing proteomic interrogations of bleb composition revealed that MLF2 possesses nucleoporin-directed chaperone activity. The characteristic ubiquitin accumulation in Torsin-deficient cells requires p97 activity, which is highly dependent on the adaptor UBXD1. p97 does not significantly depend on the Ufd1/Npl4 heterodimer to generate these ubiquitylated proteins, nor does inhibiting translation or depleting known retrotranslocons affect the ubiquitin sequestration. This work identifies a dual mechanism of proteotoxicity provoked by loss of Torsin ATPase activity via the stabilization of otherwise rapidly degraded proteins and sequestration of abundant molecular chaperones. The Torsin-regulated PQC pathway utilizes p97 and its adaptor UBXD1, while operating independently from canonical ERAD machinery. With an ever-aging population comes more burden of neurological disease driven by defective PQC, and this work advances our knowledge of potentially druggable targets for developing life-saving therapies.
Recommended Citation
Prophet, Sarah M., "Mechanisms of protein quality control at the nuclear envelope and during nuclear pore complex biogenesis" (2022). Yale Graduate School of Arts and Sciences Dissertations. 838.
https://elischolar.library.yale.edu/gsas_dissertations/838
