Oral Presentation ANZOS-Breakthrough Discoveries Joint Annual Scientific Meeting 2018

PSMD9 identified as a novel regulator of hepatic acylglycerol metabolism using an integrated systems-biology approach (#98)

Michael F Keating 1 , Tom Q Vallim 2 , Ben L Parker 3 , Marcus M Seldin 4 , Elizabeth J Tarling 2 , Sarah C Moody 1 , Yingying Lui 1 , Jake A Lusis 4 , Peter J Meikle 1 , David E James 3 , Brian G Drew 1 , Anna C Calkin 1
  1. Baker Heart and Diabetes Institute, Melbourne, VICTORIA, Australia
  2. Department of Medicine, University of California Los Angeles , Los Angeles, California, USA
  3. Metabolic Systems Biology Laboratory, Charles Perkins Centre, Sydney, New South Wales, Australia
  4. Department of Human Genetics/Medicine, University of California, Los Angeles, Los Angeles, California, USA

Disruptions in hepatic lipid homeostasis can promote the onset of conditions such as hepatosteatosis and insulin resistance. In order to interrogate hepatic lipid metabolism, we developed an integrated systems-biology discovery platform, consisting of 107 inbred mouse strains and performed proteomic and lipidomic analyses on the livers of these mice. We assessed protein:lipid associations in order to identify proteins/pathways not previously associated with hepatic lipid metabolism. This led to the identification of a protein known as 26S proteasome non-ATPase regulatory subunit 9 (PSMD9). PSMD9 highlights a previously underappreciated inter-play between proteostasis and acylglycerol metabolism. Moreover, the proteosomal associated protein was negatively associated with 65 lipid species in plasma and positively associated with 39 lipid species in the liver. Utilising the human hepatic cell line, Hep3B we sought to validate PSMD9 as a novel regulator of acylglycerol metabolism in vitro. PSMD9 overexpression resulted in a reduction in DGAT2 mRNA expression and an increase ABHD5 mRNA expression consistent with modulation of acylglycerol metabolism. Conversely, when PSMD9 was knocked down in cells DGAT2 expression increased and ABHD5 decreased. Acute over-expression of PSMD9 via an adenovirus (pAdV: PSMD9) in C57BL/6J and DBA/2J mice resulted in an accumulation of pathological acylglycerol and ceramide species in both the plasma and livers of these mice. Moreover, proteomic analysis of the livers of these mice revealed a significant enrichment of proteins associated with ER/lipid signalling and the proteasome. C57BL/6J mice injected with anti-sense oligonucleotides against PSMD9 resulted in robust hepatic knockdown and modulation of hepatic and plasma lipid species.

These findings validate the discovery platform as a resource for identifying novel regulators of hepatic lipid metabolism. Moreover, they provide a novel link between proteostasis and acylglycerol accumulation, and validate PSMD9 as a driver of acylglycerol metabolism, which has implications for hepatic steatosis.