Poster Presentation Inaugural Australian Ubiquitin Summit 2025

Similar But Not the Same: Understanding FAM115A and FAM115C structurally and biochemically (#133)

Felicia Hendrianto 1 , Anthony Cerra 1 , Nichollas Scott 2 , Simon Cobbold 1 , Marco Jochem 1 , Ethan Goddard-Borger 1 , David Komander 1 , Yuri Shibata 3
  1. WEHI, Parkville, VIC, Australia
  2. Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, Parkville, VIC, Australia
  3. Laboratory of Protein Metabolism, The University of Tokyo Graduate School of Pharmaceutical Sciences, Tokyo, Japan

FAM115A and FAM115C are two unstudied human proteins which resulted from an ancient genetic duplication(1). Both proteins are structurally similar, with two globular N-terminal domains and an M60-like catalytic domain. Interactomics studies show that FAM115A is a novel interactor of the Linear Ubiquitin Chain Assembly Complex (LUBAC)(2). LUBAC is an E3 ligase complex which assembles M1-linked (linear) ubiquitin chains and is a key regulator of NFkB mediated inflammatory signalling(3-5). Previous research from our lab verifies this interaction through cell-based pulldowns and a co-crystal structure. Moreover, FAM115A binds all ubiquitin chain types with micromolar affinity and is itself ubiquitinated. In this study, we show through immunofluorescence assays that FAM115A colocalises with ubiquitin puncta formed after chemical induction of lysosomal damage through L-Leucyl-L-Leucine methyl ester (LLOMe). This poses an exciting connection between FAM115A, ubiquitin and LUBAC in cellular repair post lysosomal damage.

The M60-like metalloprotease domain is conserved across mucinases, a class of bacterial proteases which cleave densely glycosylated O-glycoproteins termed mucins(6). We also characterise FAM115A and FAM115C M60-like domains through various structural and biochemical assays.

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  6. Shon DJ, Malaker SA, Pedram K, Yang E, Krishnan V, Dorigo O, et al. An enzymatic toolkit for selective proteolysis, detection, and visualization of mucin-domain glycoproteins. Proc Natl Acad Sci U S A. 2020;117(35):21299-307.