A MAGEL2-deubiquitinase complex modulates the ubiquitination of circadian rhythm protein CRY1

Abstract

MAGEL2 encodes the L2 member of the MAGE (melanoma antigen) protein family. Protein truncating mutations in MAGEL2 cause Schaaf-Yang syndrome, and MAGEL2 is one of a small set of genes deleted in Prader-Willi syndrome. Excessive daytime sleepiness, nighttime or early morning waking, and narcoleptic symptoms are seen in people with Prader-Willi syndrome and Schaaf-Yang syndrome, while mice carrying a gene-targeted Magel2 deletion have disrupted circadian rhythms. These phenotypes suggest that MAGEL2 is important for the robustness of the circadian rhythm. However, a cellular role for MAGEL2 has yet to be elucidated. MAGEL2 influences the ubiquitination of substrate proteins to target them for further modification or to alter their stability through proteasomal degradation pathways. Here, we characterized relationships among MAGEL2 and proteins that regulate circadian rhythm. The effect of MAGEL2 on the key circadian rhythm protein cryptochrome 1 (CRY1) was assessed using in vivo proximity labelling (BioID), immunofluorescence microscopy and ubiquitination assays. We demonstrate that MAGEL2 modulates the ubiquitination of CRY1. Further studies will clarify the cellular role MAGEL2 normally plays in circadian rhythm, in part through ubiquitination and regulation of stability of the CRY1 protein.

The N-terminal domain of the Schaaf–Yang syndrome protein MAGEL2 likely has a role in RNA metabolism

“…After data processing, 44 CtermMAGEL2-proximal proteins were identified ( Table S2 ). One protein, USP7, had been previously identified as a CtermMAGEL2 interactor by tandem affinity purification and coimmunoprecipitation, while the other proteins were not previously associated with MAGEL2 ( 8 , 9 ). While we consider these to be potential C-terminal interacting proteins, it is also possible that the N-terminal protein of MAGEL2 could alter the conformation of the C-terminal portion of the protein and influence recruitment of its binding partners.…”

“…MAGE proteins regulate protein ubiquitination, through interactions between the MHD and variable domains of E3 ubiquitin ligases and deubiquitinases, to form MAGE-RING E3 ligase complexes that serve as multifunctional hubs for the modification of key substrates in the cell ( 2 , 3 , 4 ). MAGEL2 regulates the vesicular and endosomal trafficking of membrane-bound receptors and also regulates the stability of proteins important for nuclear-cytoplasmic trafficking, cilia, and other cellular activities ( 5 , 6 , 7 , 8 , 9 , 10 ). However, functional studies have assessed only a truncated version of the MAGEL2 protein that contains the C-terminally located MHD but not the N-terminal portion of the protein ( 6 , 7 , 8 , 11 , 12 , 13 , 14 , 15 ).…”

“…Missense mutations in MAGE proteins may disrupt protein–protein interactions and function. Mutations in MAGEL2 impair its ability to facilitate retromer-dependent recycling of proteins from endosomes back to the trans -Golgi network, to promote the cell surface expression of the leptin receptor and to regulate the ubiquitination and stability of the circadian rhythm protein CRY1 ( 7 , 8 , 9 ). MAGEL2 is most highly expressed in the hypothalamus and to a lesser extent in other regions of the brain and also in the developing musculoskeletal system.…”

To Ub or not to Ub: Regulation of circadian clocks by ubiquitination and deubiquitination

“…In this paper, it was shown that MAGEL2, a protein known to interact with ubiquitin ligases and DUBs, interacts with USP7 and prevents its binding to CRY proteins. Furthermore, MAGEL2 over‐expression led to a reduction in CRY levels, showing that USP7 is required for the deubiquitination and stability of CRY proteins (Carias et al., 2020). The circadian expression of MAGEL2 suggests that the phased activity of USP7 might be regulated by the presence of MAGEL2.…”

Epigenetics in Prader-Willi Syndrome

“…However, SYS patients and mouse models with MAGEL2 mutations show a lower prevalence of overeating and obesity. Instead, it was determined that MAGEL2 functions as a ubiquitin transporter that localizes in SCN neurons and acts as a direct regulator of circadian clock proteins through ubiquitination ( Mercer et al, 2009 ; Tacer and Potts, 2017 ; Vanessa Carias et al, 2020 ).…”