Deficiency in ubiquitin ligase TRIM2 causes accumulation of neurofilament light chain and neurodegeneration

Abstract

TRIM RING finger proteins have been shown to play an important role in cancerogenesis, in the pathogenesis of some human hereditary disorders, and in the defense against viral infection, but the function of the majority of TRIM proteins remains unknown. Here, we show that TRIM RING finger protein TRIM2, highly expressed in the nervous system, is an UbcH5a-dependent ubiquitin ligase. We further demonstrate that TRIM2 binds to neurofilament light subunit (NF-L) and regulates NF-L ubiquitination. Additionally, we show that mice deficient in TRIM2 have increased NF-L level in axons and NF-L-filled axonal swellings in cerebellum, retina, spinal cord, and cerebral cortex. The axonopathy is followed by progressive neurodegeneration accompanied by juvenile-onset tremor and ataxia. Our results demonstrate that TRIM2 is an ubiquitin ligase and point to a mechanism regulating NF-L metabolism through an ubiquitination pathway that, if deregulated, triggers neurodegeneration.RING finger protein ͉ axonopathy ͉ ataxia ͉ ubiquitination U biquitination of a protein can influence its stability, interactions, activity, or intracellular localization. Three main enzyme families are involved in ubiquitination: ubiquitin activating enzymes, ubiquitin conjugating enzymes, and ubiquitin ligases. Correct localization, timing and specificity of the ubiquitination reaction are ensured mainly by ubiquitin ligases (E3s). RING finger E3s are the most abundant E3 class, characterized by the presence of the cysteine-rich RING finger domain (1). Tripartite (TRIM) RING finger proteins have been defined based on their conserved modular structure (RING finger, B-box, coiled-coil domains) as a subgroup of the RING finger proteins (2). Despite their well conserved modular structure, no common biological role has yet been discovered for TRIM proteins. Recently, some members of the TRIM family have been identified as ubiquitin ligases, involved in cancerogenesis and the defense against viral infection (3, 4). Several human diseases have been linked to mutant RING finger and TRIM E3s. Mutations in the RING finger protein parkin have been shown to trigger a juvenile form of Parkinson's disease (PD) (5). A mutant TRIM37 has been found to cause mulibrey nanism in human (6) and translocation of the TRIM gene pml has been identified in patients suffering from acute promyelocytic leukemia (3). The function of the most of TRIM proteins has not yet been discovered.TRIM2, highly expressed in the nervous system, has been linked to neuronal activity because its expression in hippocampus correlates with the activity of NMDA receptor (7). In addition, it has been shown to interact with the unconventional motor protein myosin V (7). In the present study, we demonstrate that TRIM2 is an ubiquitin ligase with its activity confined to the RING finger domain. In addition, we show that TRIM2 interacts with the neurofilament light subunit (NF-L) and that ubiquitination of NF-L significantly increases after expression of the full-length TRIM2, but not TRIM2 ligase dead muta...

DNA-binding specificity and in vivo targets of Caenorhabditis elegans nuclear factor I

“…Deficiencies in mouse and human NFI proteins show brain and neurological defects, suggesting an important function in neuronal development (2,3,19,20). Interestingly, 2 of the C. elegans targets (nhl-2 and F25H2.5) whose mouse and human orthologs (Trim2/ Trim32 and Nme2, respectively) have promoter NFI motifs have been linked to neurological defects in mice (20)(21)(22). In addition, the promoters of C. elegans nhl-2, and both mouse and human homologs of nhl-2 (Trim2/Trim32) contain NFI motifs (see Fig.…”

“…In C. elegans, NHI-2 is involved in miRNA regulation, and Trim32 has been associated with myopathy in humans and defects in neuronal differentiation in mice (20). In addition, a second nhl-2 ortholog, Trim2, has been associated with neurodegeneration in mice (22). Most recently, F25H2.5/Nme2 has been shown to have similar regulation in both C. elegans and mouse in response to knockdown of FEH-1/Fe65, a protein involved neuronal development and implicated in the processing of aberrant proteins in Alzheimer's disease (21).…”

Proteome of Acidic Phospholipid-binding Proteins

“…2C). TRIM2, a ring finger-containing ubiquitin ligase (24), also bound specifically to acidic liposomes (Fig. 2C).…”

Polyubiquitin chain-dependent protein degradation in TRIM30 cytoplasmic bodies

“…2 Contrary to the wellconserved structural organization of TRIM proteins at the N terminus, TRIM proteins possess various C-terminal domains, reflecting their versatile functions. [3][4][5][6] In addition, various C-terminal domains of individual TRIM proteins may elicit the distinct function of each TRIM protein in unique subcellular locations. For example, TRIM25 translocates to stress granules upon virus infection to interact with antiviral proteins; 7 however, TRIM27 negatively regulates CD4 + T cells by ubiquitinating PI3KC2β in recycling endosomes.…”