Elucidating the biochemical property of MURF1 E3 ligase function

Dawson, Peter William James (2024). Elucidating the biochemical property of MURF1 E3 ligase function. University of Birmingham. Ph.D.

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Abstract

The preservation of skeletal muscle mass is crucial for maintaining metabolic function, depending on the intricate balance between muscle protein synthesis (MPS) and muscle protein breakdown (MPB). Skeletal muscle atrophy occurs when MPB surpasses MPS. Although MuRF1 (Muscle-specific ubiquitin ring finger 1), an E3 ligase, is recognized as a marker for skeletal muscle atrophy, its precise molecular function in controlling muscle mass remains unclear. While MuRF1 is known for its role in degrading muscle proteins, little knowledge exists about its discreet mechanisms as a ubiquitin E3 ligase. This thesis aims to fill existing knowledge gaps, advancing our understanding of skeletal muscle mass regulation at the molecular level using in-vitro biochemical assays. The present thesis elucidates, in-vitro, the auto-ubiquitylation of MuRF1, generating various ubiquitin chain types in a UBE2-dependent manner. Furthermore, MuRF1 exhibits the ability to produce K48 and K63 polyubiquitin chains on substrates when interacting with UBE2D and UBE2E enzymes. Remarkably, it can generate unanchored K63 chains in association with UBE2N/V and mono-ubiquitylation with UBE2W. Notably, the mono-ubiquitin serves as an anchor for these unanchored K63 chains. This thesis demonstrates the direct ubiquitylation of previously suspected MuRF1 substrates and that MuRF1 ubiquitylates via the same mechanisms, whether with a substrate or through auto-ubiquitylation.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):