NSFL1C

NSFL1C/p47 is a cofactor of the AAA-ATPase VCP/p97 that directs p97 activity toward membrane remodeling and protein quality control, while also serving as a regulatory node in mitotic checkpoint control and neuronal development (PMID:35819848, PMID:37934606). The direct p47–p97 interaction is required for Golgi reassembly, as engineered antibody fragments that disrupt this interface block reassembly without affecting other p97 adaptors (PMID:35819848). In autophagy, p47 promotes autophagosome biogenesis—a function conserved in the yeast ortholog Shp1/Ubx1, which binds the ubiquitin-like protein Atg8 through a FK motif in a ubiquitin- and proteasome-independent manner (PMID:20855502)—and supports lysosomal damage repair and autophagic flux (PMID:38363674). p47 acts as a negative regulator of NF-κB signaling: it is itself degraded by the autophagy-lysosomal pathway, such that autophagy inhibition restores p47 and suppresses NF-κB activation in ATLL cells (PMID:34407152), and it routes the NF-κB modulator NEMO through endosomal trafficking to lysosomal degradation to suppress HER2+ breast cancer metastasis (PMID:38363674). In mitosis, p47 recruits the deubiquitinase USP9X to inhibit AURKB polyubiquitination, thereby limiting VCP-mediated extraction of AURKB from centromeres and enabling spindle assembly checkpoint activation (PMID:37934606). p47 also functions as a VCP cofactor that promotes tau seed amplification in a cytoplasmic processing complex (PMID:39773263). In neurons, p47 is phosphorylated downstream of a PINK1-VCP-PKA signaling axis at S176, and this phosphorylation is required for dendritic arborization and spine development (PMID:30783609, PMID:36414008). The protein comprises UBA, SEP, and UBX domains connected by intrinsically disordered regions (PMID:41188554).

1. 2007 Low

   Established that NSFL1C is a dynamically regulated signaling substrate, identifying it as a tyrosine kinase target downstream of EGFR rather than a static structural cofactor.

   Evidence Phosphotyrosyl affinity enrichment and iTRAQ/LC-MS/MS with EGF stimulation and gefitinib treatment in breast cancer

   PMID:17855441

   Open questions at the time

   • No mechanistic follow-up identifying the responsible kinase or the functional consequence of tyrosine phosphorylation on NSFL1C
   • Phosphosite not mapped to a domain or downstream effect
2. 2010 Medium

   Defined a membrane-remodeling role for the p47 ortholog beyond ER-associated degradation by showing Shp1/Ubx1 is required for autophagosome biogenesis via a direct, ubiquitin-independent interaction with Atg8.

   Evidence Yeast genetics, in vitro interaction assays, and domain mapping in S. cerevisiae

   PMID:20855502

   Open questions at the time

   • Conservation of the Atg8/LC3 interaction in mammalian p47 not directly tested
   • Whether p97 ATPase activity is required for the autophagy function not resolved here
3. 2016 Medium

   Extended the Cdc48-Ubx1/p47 complex to inner nuclear membrane protein quality control, showing it mediates ubiquitin- and proteasome-dependent turnover of a defined substrate (Asi1).

   Evidence Yeast genetics and epistasis with deletion mutants and turnover assays in S. cerevisiae

   PMID:27566164

   Open questions at the time

   • Substrate specificity determinants for Ubx1/p47 not defined
   • Mammalian counterpart of this INM pathway not addressed
4. 2018 Medium

   Placed p47 in a neuronal signaling cascade, showing PINK1 scaffolds a PINK1-VCP-PKA pathway in which PKA phosphorylates p47 at a novel S176 site to control dendritic complexity.

   Evidence RNAi knockdown, co-IP/MS proteomics, phosphorylation site mapping, and dendritic morphology readouts

   PMID:30783609

   Open questions at the time

   • How S176 phosphorylation alters p47-p97 activity mechanistically not resolved
   • Single-lab interaction network
5. 2021 Medium

   Identified p47 as a negative regulator of NF-κB whose own abundance is set by autophagic degradation, providing a route by which autophagy modulation controls NF-κB-driven proliferation.

   Evidence Pharmacological autophagy inhibition (CQ/HCQ) in ATLL cell lines, primary cells, and xenografts with NF-κB activity assays

   PMID:34407152

   Open questions at the time

   • Molecular mechanism by which p47 represses NF-κB not defined in this study
   • Autophagy receptor targeting p47 for degradation unknown
6. 2022 Medium

   Demonstrated causally that the direct p47-p97 protein-protein interaction is required for Golgi reassembly using a selective intracellular PPI inhibitor.

   Evidence Phage-display-derived antibody fragments disrupting the p97-interacting domain, with Golgi reassembly readout and selectivity profiling against other adaptors

   PMID:35819848

   Open questions at the time

   • Structural basis of the disrupted interface not resolved
   • Whether the same interface drives non-Golgi p47 functions not tested
7. 2024 Medium

   Revealed a mitotic checkpoint function in which p47 recruits USP9X to protect AURKB from VCP-mediated centromere extraction, enabling SAC activation and explaining synthetic lethality with BRCA2 deficiency.

   Evidence C. elegans synthetic-viability screen plus mammalian loss-of-function and AURKB ubiquitination/centromere localization assays

   PMID:37934606

   Open questions at the time

   • Direct USP9X-NSFL1C binding interface not mapped
   • How p47 switches between promoting and restraining VCP substrate processing unclear
8. 2024 Medium

   Connected p47's membrane-trafficking and NF-κB activities to cancer metastasis, showing p47 supports lysosomal damage repair/autophagy flux and routes NEMO to lysosomal degradation to suppress HER2+ breast cancer metastasis.

   Evidence In vivo CRISPR knockout screen with mechanistic NEMO trafficking and autophagy-flux follow-up and patient tissue analysis

   PMID:38363674

   Open questions at the time

   • Mechanism linking p47 to lysosomal membrane repair not fully resolved
   • Whether p97 ATPase activity drives NEMO trafficking not tested
9. 2025 Medium

   Identified p47 from a systematic VCP-cofactor screen as a promoter of tau seed amplification, implicating the p97-p47 axis in a cytoplasmic proteopathic processing complex.

   Evidence Knockout/knockdown screen of 30 VCP cofactors with split-APEX2 proximity labeling and tau seeding assays in biosensor cells and human neurons

   PMID:39773263

   Open questions at the time

   • Composition of the cytoplasmic processing complex not fully defined
   • Mechanism by which p47 enhances seed amplification not resolved
10. 2025 Low

    Provided the first backbone structural characterization of full-length p47, defining a UBA-SEP-UBX domain architecture linked by intrinsically disordered regions and a highly dynamic p97 complex.

    Evidence NMR backbone resonance assignments and secondary structure propensity analysis of full-length p47 and a SIM-SEP fragment

    PMID:41188554

    Open questions at the time

    • Assignments only; no high-resolution structure of p47 or the p47-p97 complex
    • No functional mutagenesis validating domain assignments

• It remains unresolved how p47's distinct functions—Golgi reassembly, autophagy, NF-κB regulation, SAC control, tau seeding, and dendrite development—are coordinated through a single p97-cofactor scaffold and switched between substrate-processing and substrate-protecting outcomes.
• No unifying model of how domain state or phosphorylation selects among p47 functions
• No structure of the active p47-p97-substrate complex