Kulin Oak, United States of America
University of Michigan NeurologyAuthor Of 1 Presentation
A FUNCTIONAL ROLE FOR UBIQUILIN-2 IN REGULATING LEVELS OF ALPHA-SYNUCLEIN
Abstract
Aims
The protein quality control protein, ubiquilin-2 (UBQLN2), co-localizes with α-synuclein aggregates in Parkinson’s disease (PD) and Lewy body dementia (LBD), implicating UBQLN2 in synucleinopathies. However, little is known about how it may interact with and clear α-synuclein. This study aimed to define the role of UBQLN2 in handling α-synuclein.
Methods
To evaluate whether UBQLN2 regulates α-synuclein clearance in vitro and in vivo, we used western blot to measure α-synuclein or pS129 α-synuclein levels in HEK-293 cells transiently expressing or deleted of UBQLN2 and in multiple transgenic mouse lines including: UBLQN2 overexpressing mice (Ub2-hi) and A53T α-synuclein mice crossed with Ub2-hi or Ub2-KO mice. We measured soluble and insoluble UBQLN2 levels in human brain lysates from PD and LBD brains to assess solubility. To determine whether UBQLN2’s action on α-synuclein is ubiquitin-dependent, we measured α-synuclein levels following transient transfection of an engineered mutant UBQLN2 (L619A) that cannot bind ubiquitin.
Results
In vitro, UBQLN2 significantly decreased soluble α-synuclein levels. In vivo, α-synuclein levels decreased in UBQLN2-overexpressing mice. A53T α-synuclein and pS129 levels were unchanged in A53TxUb2-hi mice versus A53T controls but were significantly increased in A53TXUb2-KO mice. Human brain tissue studies revealed increased insoluble UBQLN2 levels in PD and LBD. Unexpectedly, L619A UBQLN2 was more effective than wild-type UBQLN2 at reducing α-synuclein levels, implying a ubiquitin-independent effect.
Conclusions
Our results support a functional role for UBQLN2 in regulating a-synuclein levels and that UBQLN2 solubility is altered in PD and LBD disease brains. Ongoing studies seek to elucidate the mechanism by which UBQLN2 helps clear a-synuclein.