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Mkrn3 functions as a novel ubiquitin E3 ligase to inhibit Nptx1 during puberty initiation.

ABSTRACT: Central precocious puberty (CPP) is attributed to the disorder of some trigger factors those can activate the hypothalamic-pituitary-gonadal axis controlled by GnRH neurons. Many recent studies reveal one of those trigger factors, Makorin ring finger protein 3 (Mkrn3), whose loss-of-function mutations are implicated in CPP. Although Mkrn3 contained zinc Ring finger domain is considered as a putative E3 ubiquitin ligase, its actual function is never reported. Here, our results demonstrated that in mice hypothalamus before and when puberty initiated, Mkrn3 expressed the reversed tendency with Nptx1, which is an important secreted protein for neuron development. Furthermore, our data manifested that Mkrn3 interacted and suppressed Nptx1 activity. And the Ring finger domain of Mkrn3 contained was determined to be essential for binding with Nptx1 for its polyubiquitination during the puberty initiation. Our study shed light on the molecular insights into the function of Mkrn3 in the events of puberty initiation.

SUBMITTER: Liu H

PROVIDER: S-EPMC5689596 | biostudies-literature | 2017 Oct

REPOSITORIES: biostudies-literature

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Mkrn3 functions as a novel ubiquitin E3 ligase to inhibit Nptx1 during puberty initiation.

Liu Huifang H Kong Xiangxin X Chen Fengling F

Oncotarget 20170718 49

Central precocious puberty (CPP) is attributed to the disorder of some trigger factors those can activate the hypothalamic-pituitary-gonadal axis controlled by GnRH neurons. Many recent studies reveal one of those trigger factors, Makorin ring finger protein 3 (Mkrn3), whose loss-of-function mutations are implicated in CPP. Although Mkrn3 contained zinc Ring finger domain is considered as a putative E3 ubiquitin ligase, its actual function is never reported. Here, our results demonstrated that i ...[more]

PMID: 29156706

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Project description:Coronavirus disease 2019, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has led to an unprecedented public health crisis worldwide. Though the host produces interferons (IFNs) and restriction factors to suppress virus infection, SARS-CoV-2 has evolved multiple strategies to inhibit the antiviral responses. Understanding host restriction factors and viral escape mechanisms is conducive to developing effective anti-SARS-CoV-2 drugs. Here, we constructed SARS-CoV-2 nucleocapsid (2N) protein- and green fluorescent protein (GFP)-stably expressing cells that were transfected with polyinosinic-polycytidylic acid (poly(I:C)) to activate IFN responses. The transcriptome analysis showed that poly(I:C)-induced IFN responses were inhibited by the SARS-CoV-2 N protein. Further analysis revealed that 2N inhibited the production of IFN-stimulated genes by suppressing early growth response gene-1 (EGR1) expression, a transcription factor that can regulate multiple cellular processes. The ectopic expression of EGR1 remarkably reduced 2N expression and suppressed SARS-CoV-2 replication. Mechanistically, EGR1 promoted expression of IFN-regulated antiviral protein (IRAV), which interacted with 2N to induce its degradation via the E3 ubiquitin ligase MARCH8 with the cargo receptor NDP52 in a lysosome-dependent pathway. MARCH8 catalyzed the K48-linked polyubiquitination of 2N at the lysine residue 143, and knockout of endogenous MARCH8 reversed IRAV-mediated 2N degradation. Additionally, the overexpression of IRAV or MARCH8 could inhibit SARS-CoV-2 replication. Our findings reveal that EGR1 is a new host restriction factor to inhibit SARS-CoV-2 replication through the E3 ubiquitin ligase MARCH8, which would contribute to understanding the pathogenesis of emerging coronaviruses. IMPORTANCE Emerging vaccine-breakthrough severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants highlight an urgent need for novel antiviral therapies. Understanding the pathogenesis of coronaviruses is critical for developing antiviral drugs. Here, we demonstrate that the SARS-CoV-2 N protein suppresses interferon (IFN) responses by reducing early growth response gene-1 (EGR1) expression. The overexpression of EGR1 inhibits SARS-CoV-2 replication by promoting IFN-regulated antiviral protein expression, which interacts with and degrades SARS-CoV-2 N protein via the E3 ubiquitin ligase MARCH8 and the cargo receptor NDP52. The MARCH8 mutants without ubiquitin ligase activity are no longer able to degrade SARS-CoV-2 N proteins, indicating that MARCH8 degrades SARS-CoV-2 N proteins dependent on its ubiquitin ligase activity. This study found a novel immune evasion mechanism of SARS-CoV-2 utilized by the N protein, which is helpful for understanding the pathogenesis of SARS-CoV-2 and guiding the design of new prevention strategies against the emerging coronaviruses.

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Mkrn3 functions as a novel ubiquitin E3 ligase to inhibit Nptx1 during puberty initiation.

Publications

Mkrn3 functions as a novel ubiquitin E3 ligase to inhibit Nptx1 during puberty initiation.

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