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Other entities represented in this entry:
HGNC Approved Gene Symbol: USP8
Cytogenetic location: 15q21.2 Genomic coordinates (GRCh38): 15:50,424,405-50,514,421 (from NCBI)
| Location | Phenotype |
Phenotype MIM number |
Inheritance |
Phenotype mapping key |
|---|---|---|---|---|
| 15q21.2 | Pituitary adenoma 4, ACTH-secreting, somatic | 219090 | 3 |
During analysis of randomly sampled human coding sequences from the myeloid cell line KG-1, Nomura et al. (1994) identified a novel cDNA, which they referred to as KIAA0055, that was related to the tre2 oncogene. Janssen et al. (1998) found that HUMORF8 encodes a putative deubiquitinating enzyme.
By analyzing the E3 ubiquitin ligase NRDP1 (RNF41; 620051) ectopically expressed in COS7 cells, Wu et al. (2004) showed that NRDP1 was an intrinsically unstable protein in cells, as it was self-ubiquitinated and degraded in a proteasome-dependent manner. The authors identified USP8 as a deubiquitinating enzyme that stabilized the NRDP1 protein. Specific interaction of USP8 with NRDP1 was mediated by the rhodanese domain of USP8, and the 2 proteins formed a functional complex in cells that stabilized the NRDP1 protein. Mutation analysis revealed that the USP8 catalytic domain was moderately capable of mediating NRDP1 stabilization, but full stability required NRDP1 association through the USP8 rhodanese domain.
By coimmunoprecipitation analysis of HeLa cell lysates, Mizuno et al. (2007) showed that the 14-3-3 proteins YWHAE (605066), YWHAG (605356), and YWHAZ (601288) bound mouse Usp8. Binding of 14-3-3 proteins to Usp8 was inhibited by phosphatase treatment, by mutating the consensus 14-3-3-binding motif in Usp8, or by competition with a phosphorylated 14-3-3-binding peptide. The authors identified ser680 within the 14-3-3-binding motif as the major phosphorylation site of mouse Usp8. Mutation of ser680 led to enhanced ubiquitin isopeptidase activity of Usp8 against polyubiquitin chains and human EGFR (131550). Addition of mouse Ywhae inhibited USP8 activity. Usp8 was dephosphorylated at ser680 and dissociated from 14-3-3 proteins in M phase, resulting in enhanced Usp8 activity during cell division. Mizuno et al. (2007) concluded that USP8 is catalytically inhibited in a phosphorylation-dependent manner by 14-3-3 proteins during interphase and that the regulation is discontinued in M phase.
Berlin et al. (2010) found that depletion of USP8 in HeLa cells accelerated EGFR degradation and that USP8 mitigated EGFR degradation via an HRS (HGS; 604375)-dependent pathway. Mutation analysis using mouse proteins showed that regulation of EGFR ubiquitination required a central region of Usp8 containing 3 RxxK motifs that had low-affinity interactions with the SH3 domains of the ESCRT-0 proteins Stam1 (601899) and Stam2 (606244). Usp8-mediated deubiquitination slowed progression of EGFR past the early-to-recycling endosome circuit in an RxxK motif-dependent manner. Berlin et al. (2010) concluded that the USP8-STAM complex is a protective mechanism that regulates early endosomal sorting of EGFR between pathways destined for lysosomal degradation and recycling.
Using a yeast 2-hybrid screen of a human brain cDNA library with the ESCRT-0 component HRS as bait, followed by biochemical analyses, Sirisaengtaksin et al. (2014) found that HRS interacted with UBE4B (613565). Further analysis using human neuroblastoma and HeLa cells showed binding of UBE4B to endosomes via its interaction with HRS and ubiquitination and degradation of EGFR that had bound to HRS. Binding of the ESCRT-0 component STAM to HRS did not affect interaction of HRS with UBE4B. The deubiquitinating enzyme USP8 was also required for EGFR sorting and degradation. Sirisaengtaksin et al. (2014) proposed that UBE4B, the ESCRT-0 complex, and USP8 couple the ubiquitination and sorting machineries to promote endosomal sorting and lysosomal degradation of EGFR.
Using immunoblot and confocal microscopy analyses, MacDonald et al. (2014) demonstrated that depletion of USP8 in HeLa cells affected retromer-dependent shuttling of cation-independent M6PR (IGF2R; 147280) between the sorting endosome and biosynthetic pathway, resulting in a steady-state redistribution of cation-independent M6PR from the trans-Golgi network to endosomal compartments. This redistribution led to a defect in sorting of lysosomal enzymes, as shown by increased levels of unprocessed cathepsin D (CTSD; 116840) secreted from cells. Normal receptor distribution was restored by expression of small interfering RNA-resistant USP8, but not by expression of catalytically inactive USP8 or truncated USP8 mutants lacking the domain required for endosomal localization. MacDonald et al. (2014) proposed that the effects of USP8 depletion may be due to loss of ESCRT-0 components that associate with the retromer components VPS35 (601501) and SNX1 (601272). They suggested that failure to efficiently deliver lysosomal enzymes may also contribute to the observed block in receptor tyrosine kinase degradation.
Fusion Gene
Janssen et al. (1998) analyzed DNA from a patient with chronic myeloproliferative disorder. They identified an oncogenic fusion of the 5-prime end of p85-beta (603157) with the 3-prime end of HUMORF8.
ACTH-Secreting Pituitary Adenomas, Somatic
By screening large series of pituitary adenomas, Reincke et al. (2015), Ma et al. (2015), and Perez-Rivas et al. (2015) identified heterozygous somatic mutations in the USP8 gene in ACTH-secreting pituitary adenomas (PITA4; 219090), which result in Cushing disease, but not in any other type of pituitary adenomas tested. All of the mutations occurred within or adjacent to the 14-3-3 (see YWHAE, 605066)-binding motif in exon 14. In all 3 studies, the majority of the mutations occurred at 2 conserved residues: ser718 and pro720 (see, e.g., 603158.0002-603158.0004). Functional studies showed that the mutations reduced the interaction between USP8 and 14-3-3 and enhanced USP8 activity. USP8 mutants diminished epidermal EGFR ubiquitination and induced promoter activity of POMC (176830), which encodes the precursor of ACTH. Ma et al. (2015) showed that USP8 knockdown or treatment with gefitinib, an EGFR inhibitor, significantly reduced ACTH secretion in primary USP8-mutated corticotropin adenoma cells but not in wildtype cells.
Associations Pending Confirmation
For discussion of a possible association between variation in the USP8 gene and spastic paraplegia, see 603158.0001.
This variant is classified as a variant of unknown significance because its contribution to spastic paraplegia has not been confirmed.
In 3 affected sibs in a consanguineous family (family 882) segregating spastic paraplegia, Novarino et al. (2014) identified a homozygous 928C-A transversion in the USP8 gene, resulting in a gln310-to-lys (Q310K) substitution. The 3 sibs (2 boys and 1 girl) all presented at 20 months of age, and by middle childhood, they were hypertonic, with 2 of them requiring surgery for tendon releases. All could walk with support, with a spastic gait. All had clonus and 1 had pes equinovarus. All 3 had normal brain MRIs; 2 had normal cognition and 1 had borderline IQ. Morpholino knockdown of Usp8 in zebrafish resulted in a movement disorder. The ethnicity of the family was not provided. Novarino et al. (2014) labeled the disorder spastic paraplegia-59 (SPG59).
In a screen of 108 ACTH-secreting pituitary adenomas (PITA4; 219090), Ma et al. (2015) identified 17 different heterozygous somatic mutations in the USP8 gene, including a c.2159C-G somatic mutation, resulting in a pro720-to-arg (P720R), as 1 of 3 recurrent mutations accounting for over 77% of the USP8-mutated tumors. None of the 17 mutations were found in the dbSNP (build 138) or 1000 Genomes Project databases. Functional studies in 293T cells showed that the mutant failed to bind 14-3-3 protein, and in HeLa cells, the mutant showed reduced EGFR ubiquitination compared to wildtype, indicating that the mutation results in a gain of function.
By Sanger sequencing in 134 corticotroph adenomas from patients with Cushing disease, Perez-Rivas et al. (2015) identified USP8 mutations in 48 tumors, including the P720R mutation in 2 (4.1%).
In a screen of 108 ACTH-secreting pituitary adenomas (PITA4; 219090), Ma et al. (2015) identified 17 different heterozygous somatic mutations in the USP8 gene, including a ser718-to-pro (S718P) as 1 of 3 recurrent mutations accounting for over 77% of the USP8-mutated tumors. None of the 17 mutations were found in the dbSNP (build 138) or 1000 Genomes Project databases. Functional studies in 293T cells showed that the mutant failed to bind 14-3-3 protein, and in HeLa cells, the mutant showed reduced EGFR ubiquitination compared to wildtype, indicating that the mutation results in a gain of function.
By Sanger sequencing in 134 corticotroph adenomas from patients with Cushing disease, Perez-Rivas et al. (2015) identified USP8 mutations in 48 tumors, including the S218P mutation in 14 (28.6%).
In a screen of 108 ACTH-secreting pituitary adenomas (PITA4; 219090), Ma et al. (2015) identified 17 different heterozygous somatic mutations in the USP8 gene, including a 3-bp deletion, resulting in deletion of serine-718 (ser718del), as 1 of 3 recurrent mutations accounting for over 77% of the USP8-mutated tumors. None of the 17 mutations were found in the dbSNP (build 138) or 1000 Genomes Project databases. Functional studies in 293T cells showed that the mutant failed to bind 14-3-3 protein, and in HeLa cells, the mutant showed reduced EGFR ubiquitination compared to wildtype, indicating that the mutation results in a gain of function.
By Sanger sequencing in 134 corticotroph adenomas from patients with Cushing disease, Perez-Rivas et al. (2015) identified heterozygous USP8 mutations in 48 tumors, including a 3-bp deletion (c.2155_2157delTCC), resulting in the deletion of ser718, in 11 (22.4%).
Berlin, I., Schwartz, H., Nash, P. D. Regulation of epidermal growth factor receptor ubiquitination and trafficking by the USP8-STAM complex. J. Biol. Chem. 285: 34909-34921, 2010. [PubMed: 20736164] [Full Text: https://doi.org/10.1074/jbc.M109.016287]
Janssen, J. W. G., Schleithoff, L., Bartram, C. R., Schulz, A. S. An oncogenic fusion product of the phosphatidylinositol 3-kinase p85-beta subunit and HUMORF8, a putative deubiquitinating enzyme. Oncogene 16: 1767-1772, 1998. [PubMed: 9582025] [Full Text: https://doi.org/10.1038/sj.onc.1201695]
Ma, Z.-Y., Song, Z.-J., Chen, J.-H., Wang, Y.-F., Li, S.-Q., Zhou, L.-F., Mao, Y., Li, Y.-M., Hu, R.-G., Zhang, Z.-Y., Ye, H.-Y., Shen, M., and 34 others. Recurrent gain-of function USP8 mutations in Cushing's disease. Cell Res. 25: 306-317, 2015. [PubMed: 25675982] [Full Text: https://doi.org/10.1038/cr.2015.20]
MacDonald, E., Urbe, S., Clague, M. J. USP8 controls the trafficking and sorting of lysosomal enzymes. Traffic 15: 879-888, 2014. [PubMed: 24894536] [Full Text: https://doi.org/10.1111/tra.12180]
Mizuno, E., Kitamura, N., Komada, M. 14-3-3-dependent inhibition of the deubiquitinating activity of UBPY and its cancellation in the M phase. Exp. Cell Res. 313: 3624-3634, 2007. [PubMed: 17720156] [Full Text: https://doi.org/10.1016/j.yexcr.2007.07.028]
Nomura, N., Nagase, T., Miyajima, N., Sazuka, T., Tanaka, A., Sato, S., Seki, N., Kawarabayasi, Y., Ishikawa, K., Tabata, S. Prediction of the coding sequences of unidentified human genes. II. The coding sequences of 40 new genes (KIAA0041-KIAA0080) deduced by analysis of cDNA clones from human cell line KG-1. DNA Res. 1: 223-229, 1994. [PubMed: 7584044] [Full Text: https://doi.org/10.1093/dnares/1.5.223]
Novarino, G., Fenstermaker, A. G., Zaki, M. S., Hofree, M., Silhavy, J. L., Heiberg, A. D., Abdellateef, M., Rosti, B., Scott, E., Mansour, L., Masri, A., Kayserili, H., and 41 others. Exome sequencing links corticospinal motor neuron disease to common neurodegenerative disorders. Science 343: 506-511, 2014. [PubMed: 24482476] [Full Text: https://doi.org/10.1126/science.1247363]
Perez-Rivas, L. G., Theodoropoulou, M., Ferrau, F., Nusser, C., Kawaguchi, K., Stratakis, C. A., Faucz, F. R., Wildemberg, L. E., Assie, G., Beschorner, R., Dimopoulou, C., Buchfelder, M., and 12 others. The gene of the ubiquitin-specific protease 8 is frequently mutated in adenomas causing Cushing's disease. J. Clin. Endocr. Metab. 100: E997-E1004, 2015. Note: Electronic Article. [PubMed: 25942478] [Full Text: https://doi.org/10.1210/jc.2015-1453]
Reincke, M., Sbiera, S., Hayakawa, A., Theodoropoulou, M., Osswald, A., Beuschlein, F., Meitinger, T., Mizuno-Yamasaki, E., Kawaguchi, K., Saeki, Y., Tanaka, K., Wieland, T., Graf, E., Saeger, W., Ronchi, C. L., Allolio, B., Buchfelder, M., Strom, T. M., Fassnacht, M., Komada, M. Mutations in the deubiquitinase gene USP8 cause Cushing's disease. Nature Genet. 47: 31-38, 2015. [PubMed: 25485838] [Full Text: https://doi.org/10.1038/ng.3166]
Sirisaengtaksin, N., Gireud, M., Yan, Q., Kubota, Y., Meza, D., Waymire, J. C., Zage, P. E., Bean, A. J. UBE4B protein couples ubiquitination and sorting machineries to enable epidermal growth factor receptor (EGFR) degradation. J. Biol. Chem. 289: 3026-3039, 2014. [PubMed: 24344129] [Full Text: https://doi.org/10.1074/jbc.M113.495671]
Wu, X., Yen, L., Irwin, L., Sweeney, C., Carraway, K. L. Stabilization of the E3 ubiquitin ligase Nrdp1 by the deubiquitinating enzyme USP8. Molec. Cell. Biol. 24: 7748-57, 2004. [PubMed: 15314180] [Full Text: https://doi.org/10.1128/MCB.24.17.7748-7757.2004]