Semester

Fall

Date of Graduation

2022

Document Type

Dissertation

Degree Type

PhD

College

School of Medicine

Department

Biochemistry

Committee Chair

David M Smith

Committee Co-Chair

Aaron Robart

Committee Member

Aaron Robart

Committee Member

Bradley Webb

Committee Member

Visvanathan Ramamurthy

Committee Member

Werner Geldenhuys

Abstract

Virtually all cellular processes are precisely regulated by the proteasome which is the primary enzyme responsible for the degradation of misfolded, damaged, or no longer necessary soluble proteins. To prevent any untimely degradation of these target protein substrates and protect the cell, the proteasome is tightly regulated via adaptor proteins, known as proteasomal regulators. There are many classes of proteasomal regulators each with their own unique structures, functions, and effects on protein degradation through the proteasome. One such class is the 11S family of proteasomal regulators which are also referred to as PA26/28, or REG. The 11S family are ATP-independent and are found in the majority of multicellular eukarya, with a notable exception being bird species. Mammalian 11S family members have three distinct homologs: PA28α, PA28β, and PA28γ. PA28γ specifically has been implicated in certain cancers, systemic lupus erythematosus (SLE), and spinal and bulbar muscular atrophy (SMBA), however its proteasomal regulatory mechanism is contested and not well understood. Here, we show that PA28γ allosterically activates the trypsin-like catalytic site, without inhibiting or modifying the other proteasomal active sites, while maintaining a similar quaternary structure to other well-characterized 11S family members. Our results provide a definitive mechanism of proteasomal activation via PA28γ. This information provides a clear molecular model to feasibly design PA28γ-mimetic or -inhibitor drugs to modulate proteasome function based upon the disease that is being treated.

Embargo Reason

Publication Pending

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