Proteomic Analysis and Identification of Cellular Interactors of the Giant Ubiquitin Ligase HERC2

HERC2 is a large E3 ubiquitin ligase
with multiple structural domains
that has been implicated in an array of cellular processes. Mutations
in HERC2 are linked to developmental delays and impairment caused
by nervous system dysfunction, such as Angelman Syndrome and autism-spectrum
disorders. However, HERC2 cellular activity and regulation remain
poorly understood. We used a broad proteomic approach to survey the
landscape of cellular proteins that interact with HERC2. We identified
nearly 300 potential interactors, a subset of which we validated binding
to HERC2. The potential HERC2 interactors included the eukaryotic
translation initiation factor 3 complex, the intracellular transport
COPI coatomer complex, the glycogen regulator phosphorylase kinase,
beta-catenin, PI3 kinase, and proteins involved in fatty acid transport
and iron homeostasis. Through a complex bioinformatic analysis of
potential interactors, we linked HERC2 to cellular processes including
intracellular protein trafficking and transport, metabolism of cellular
energy, and protein translation. Given its size, multidomain structure,
and association with various cellular activities, HERC2 may function
as a scaffold to integrate protein complexes and bridge critical cellular
pathways. This work provides a significant resource with which to
interrogate HERC2 function more deeply and evaluate its contributions
to mechanisms governing cellular homeostasis and disease.