PERK Kinase Activity is Regulated by Copper Binding-A New Regulatory Paradigm for Modulation of ER Stress Tolerance

PERK is a kinase that, in response to ER stress, mediates duplicitous homeostatic and pro-apoptotic signaling. Thus, intricate regulation is required for physiologic function. Attempts to modulate PERK activity have shown that the determinants of adaptive vs. mal-adaptive signaling remain ambiguous. Here, with purified protein, we provide direct evidence that PERK binds copper, identify the residues that coordinate binding, and demonstrate that binding is necessary for kinase activity. Furthermore cellular PERK activity can be modulated via copper availability, and this regulatory relationship can be manipulated to dictate ER stress tolerance. Critically, these phenomenon translate to phenotypes in vivo, as C. elegans harboring a "copper-binding mutant" of PERK exhibit enhanced ER-stress sensitivity. The copper-PERK paradigm adds onto a new class of dynamic copper-binding enzymes and implicates that copper homeostasis, as a regulator of PERK, may constitute a previously unknown variable to resolve long-standing ambiguity in endeavors to therapeutically target PERK.