CAREER: The Effects of Liquid-Liquid Phase Separation on Ubiquilin Chaperone and Triage Activity

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This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2). In response to cellular stress, some proteins form liquid-like droplets by a process called Liquid-Liquid Phase Separation (LLPS), but the specific effects of LLPS on protein activity are poorly understood. Other proteins, referred to as chaperones, have the role of mitigating cellular stress. This project focuses on a family of proteins called Ubiquilins that are considered chaperones. Ubiquilins can undergo LLPS and mitigate cellular stress by preventing the formation of toxic protein aggregates. The goal of this project is to understand how LLPS affects the ability of Ubiquilins to either assist proteins to insert into the cell membrane or degrade proteins that cannot properly insert, roles that are essential to prevent the accumulation of toxic protein aggregates and other forms of cell stress. The research project is intimately integrated with three key outreach activities targeted to children in foster care and students at Toledo Public Schools (TPS). First, in partnership with Lucas County Children Services and TPS, there will be science day at Elevate Summer Camp, which provides a safe summer environment for at risk youth, including foster youth. Campers will learn about STEM careers and conduct basic LLPS experiments. Second, TPS high school students will do a field trip to the University of Toledo to tour laboratories, demystify the college admission process, and learn about STEM research opportunities. Third, TPS students and foster youth will be mentored in a summer research internship. These outreach activities will increase scientific literacy, improve STEM education, and promote the full participation of foster youth and TPS students in STEM fields. American Rescue Plan funding is used to support this early career investigator at a critical stage in his career.Humans have three broadly expressed Ubiquilin paralogs: Ubqln1, Ubqln2, and Ubqln4. Ubiquilins have been shown to bind to uninserted membrane proteins and provide additional opportunities for productive membrane insertion. Ubiquilins can also interact with the Ubiquitin-Proteasome System to facilitate client protein degradation. Ubqln2 has been shown to undergo LLPS, but how LLPS affects Ubqln2 activity is unknown. This project focuses on determining how LLPS affects the ability of Ubiquilins to chaperone and triage uninserted membrane proteins. The project’s goals are to: (1) determine how LLPS affects the ability of Ubiquilins to facilitate client protein ubiquitination and degradation and (2) determine how LLPS affects the ability of Ubiquilins to bind membrane proteins and facilitate their insertion into the lipid bilayer. Completion of this project will facilitate the principal investigator’s long-term goal of understanding the functional significance of LLPS on Ubiquilin activity.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.