UC Santa Barbara

Proteotoxic stress drives the progression of numerous degenerative diseases including Type I diabetes, Huntingtin’s Disease, Parkinson’s Disease, and retinitis pigmentosa, a degenerative blinding disease. Cells respond to misfolded proteins by activating the unfolded protein response (UPR), including endoplasmic-reticulum-associated-protein-degradation (ERAD) and proteasomal degradation, but persistent stress triggers apoptosis. Enhancing ERAD is a promising therapeutic approach for protein misfolding diseases. From plants to humans, loss of the zinc transporter ZIP7 causes ER stress; however, the mechanism is unknown. We used Drosophila melanogaster to genetically manipulate ZIP7 and investigate its function in vivo. Here, we show that ZIP7-mediated Zn2+ transport enhances ERAD and that cytosolic Zn2+ is limiting for deubiquitination of client proteins by the Rpn11 Zn2+ metalloproteinase as they enter the proteasome. We then decided to test ZIP7’s effects in a fly model of retinitis pigmentosa. Interestingly, we found ZIP7 overexpression rescues defective vision and photoreceptor degeneration caused by misfolded rhodopsin in Drosophila. We have begun a collaboration looking into whether ZIP7 can prevent or suppress mutant Rhodopsin-mediated neurodegeneration in human retinal organoids. Additionally, these results prompted a screen for potential ZIP7 rescue of other aggregate-prone proteins associated with neurodegenerative diseases. So far, we found that ZIP7 rescues photoreceptor degeneration caused by Aβ42 and Vap33. Further study of ZIP7, a novel component of ERAD, holds significant promise for therapeutic advancements in protein-folding disorders.