id: O60238
gene_symbol: BNIP3L
product_type: PROTEIN
status: COMPLETE
taxon:
  id: NCBITaxon:9606
  label: Homo sapiens
description: 'BNIP3L (NIX) is a tail-anchored, atypical BH3-containing member of the BNIP3/NIP3 family that is inserted into the mitochondrial outer membrane via its C-terminal transmembrane helix, with its N-terminal disordered region facing the cytosol. Its principal, conserved function is as a selective autophagy (mitophagy) receptor: an LC3-interacting region in the cytosolic domain binds Atg8-family proteins (LC3 and GABARAP/GABARAPL1/GABARAPL2), tethering mitochondria to the forming autophagosome and driving their programmed autophagic clearance. This is most prominent during terminal erythroid/reticulocyte maturation and other developmentally programmed or stress-induced episodes of mitochondrial turnover. NIX also participates in non-canonical mitochondrial quality control through ROS-dependent interaction with SPATA18/MIEAP, and under hypoxia it is induced by HIF and promotes pro-survival macroautophagy via its atypical BH3 domain. Although first described as a pro-apoptotic BCL-2-family protein, its effects on cell death are context-dependent and direction-dependent (it can both promote and inhibit cell death) and act largely through mitochondrial membrane permeability/necrosis rather than classical cytochrome-c/caspase apoptosis. Beyond mitochondria, NIX can independently localize to peroxisomes and act as a selective autophagy receptor for their clearance (pexophagy), broadening its cargo selectivity. NIX abundance is held in check by constitutive ubiquitin-mediated turnover: an SCF(FBXL4) ubiquitin ligase complex at the mitochondrial outer membrane, with the phosphatase PPTC7 as a cofactor, degrades NIX (and BNIP3) to restrain basal mitophagy, while hypoxia/HIF signaling induces NIX transcription. NIX is also exploited by several viruses, which hijack NIX-mediated mitophagy to degrade mitochondrial antiviral signaling components.'
alternative_products:
- name: '1'
  id: O60238-1
- name: '2'
  id: O60238-2
  sequence_note: VSP_056248
existing_annotations:
- term:
    id: GO:0043065
    label: positive regulation of apoptotic process
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: involved_in
  review:
    summary: NIX/BNIP3L was first characterized as a pro-apoptotic BCL-2/NIP3-family protein and can promote cell death in some contexts, but this is direction-dependent and atypical (necrosis/membrane permeability rather than classical caspase apoptosis).
    action: KEEP_AS_NON_CORE
    reason: The pro-apoptotic role is genuine but secondary and context-dependent relative to the conserved mitophagy-receptor function; the same gene also has negative-regulation-of-apoptosis annotations, underscoring that cell-death regulation is contextual.
    supported_by:
    - reference_id: PMID:9973195
      supporting_text: Overexpression of BNIP3alpha in transfected cells results in apoptosis and suppresses the antiapoptosis activity of E1B-19K and BCL-xL.
      reference_section_type: ABSTRACT
    - reference_id: PMID:21264228
      supporting_text: in contrast to other mitochondrial Bcl-2 family proteins, NIX and BNIP3 are not involved in the release of cytochrome c and the resulting caspase-dependent apoptosis, but rather related to necrosis through the regulation of mitochondrial permeability transition pore (MPTP)
      reference_section_type: INTRODUCTION
- term:
    id: GO:0043653
    label: mitochondrial fragmentation involved in apoptotic process
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: involved_in
  review:
    summary: Mitochondrial fragmentation in an apoptotic context is a secondary, contextual aspect of NIX biology rather than its core mitophagy-receptor function.
    action: KEEP_AS_NON_CORE
    reason: NIX can promote mitochondrial membrane permeabilization/necrosis-related death, but the conserved core function is selective autophagic clearance of mitochondria, not apoptotic fragmentation.
    supported_by:
    - reference_id: PMID:21264228
      supporting_text: in contrast to other mitochondrial Bcl-2 family proteins, NIX and BNIP3 are not involved in the release of cytochrome c and the resulting caspase-dependent apoptosis, but rather related to necrosis through the regulation of mitochondrial permeability transition pore (MPTP)
      reference_section_type: INTRODUCTION
- term:
    id: GO:0005783
    label: endoplasmic reticulum
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: is_active_in
  review:
    summary: ER localization is reported for NIX (it was detected in nuclear envelope, ER and mitochondria, and linked to ER Ca2+ handling), but it is a secondary site relative to the mitochondrial outer membrane where the mitophagy-receptor function operates.
    action: KEEP_AS_NON_CORE
    reason: ER localization is documented but is not the primary functional compartment; the is_active_in qualifier overstates ER as a site of NIX activity.
    supported_by:
    - reference_id: PMID:10381623
      supporting_text: localizes in nuclear envelope, endoplasmic reticulum and mitochondria
      reference_section_type: ABSTRACT
    - reference_id: PMID:21264228
      supporting_text: NIX was also shown to localize to endoplasmic reticulum (ER) and increase the store of Ca++, leading to Ca++ influx into mitochondria and cell death
      reference_section_type: INTRODUCTION
- term:
    id: GO:0005741
    label: mitochondrial outer membrane
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: is_active_in
  review:
    summary: The mitochondrial outer membrane is the core functional location of NIX, where its C-terminal transmembrane anchor inserts and its cytosolic LIR engages the autophagy machinery.
    action: ACCEPT
    reason: This is the principal functional compartment for the mitophagy-receptor activity and is strongly supported by multiple independent studies.
    supported_by:
    - reference_id: PMID:20200478
      supporting_text: Nix is a mitochondrial outer membrane protein that is required for mitochondrial clearance during erythrocyte maturation.
      reference_section_type: ABSTRACT
    - reference_id: PMID:21264228
      supporting_text: A mitochondrial outer membrane protein NIX interacted with Mieap in a ROS-dependent manner via the BH3 domain of NIX and the coiled-coil domain of Mieap.
      reference_section_type: ABSTRACT
- term:
    id: GO:0005634
    label: nucleus
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: is_active_in
  review:
    summary: A nuclear/nuclear-envelope localization derives from the original B5 study; it is weakly supported and is not the functional compartment for the mitophagy-receptor role.
    action: MARK_AS_OVER_ANNOTATED
    reason: 'is_active_in nucleus is not supported by a defined nuclear function; the only relevant primary data describe nuclear envelope localization, likely reflecting tail-anchored membrane behavior, not nucleoplasmic activity.'
    supported_by:
    - reference_id: PMID:10381623
      supporting_text: localizes in nuclear envelope, endoplasmic reticulum and mitochondria
      reference_section_type: ABSTRACT
- term:
    id: GO:0005635
    label: nuclear envelope
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: is_active_in
  review:
    summary: Nuclear envelope localization is reported in the original B5 study (with associated lamin binding), but it is a secondary, weakly characterized site rather than the functional mitophagy compartment.
    action: KEEP_AS_NON_CORE
    reason: Nuclear envelope localization is documented experimentally but is not where the conserved mitophagy-receptor function acts; retained as non-core.
    supported_by:
    - reference_id: PMID:10381623
      supporting_text: localizes in nuclear envelope, endoplasmic reticulum and mitochondria
      reference_section_type: ABSTRACT
- term:
    id: GO:0005635
    label: nuclear envelope
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  qualifier: located_in
  review:
    summary: Automated subcellular-location transfer of nuclear envelope localization, consistent with the experimental B5 data.
    action: KEEP_AS_NON_CORE
    reason: Consistent with documented nuclear envelope localization but secondary to the mitochondrial outer membrane function.
    supported_by:
    - reference_id: PMID:10381623
      supporting_text: localizes in nuclear envelope, endoplasmic reticulum and mitochondria
      reference_section_type: ABSTRACT
- term:
    id: GO:0005740
    label: mitochondrial envelope
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  qualifier: located_in
  review:
    summary: Mitochondrial envelope is a less specific parent of the mitochondrial outer membrane, where NIX is actually anchored.
    action: MODIFY
    reason: The more precise and well-supported localization is the mitochondrial outer membrane; replace the broader envelope term.
    proposed_replacement_terms:
    - id: GO:0005741
      label: mitochondrial outer membrane
    supported_by:
    - reference_id: PMID:20200478
      supporting_text: Nix is a mitochondrial outer membrane protein that is required for mitochondrial clearance during erythrocyte maturation.
      reference_section_type: ABSTRACT
- term:
    id: GO:0005741
    label: mitochondrial outer membrane
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  qualifier: located_in
  review:
    summary: Automated location transfer of the well-supported mitochondrial outer membrane localization.
    action: ACCEPT
    reason: Strongly supported as the core functional compartment.
    supported_by:
    - reference_id: PMID:20200478
      supporting_text: Nix is a mitochondrial outer membrane protein that is required for mitochondrial clearance during erythrocyte maturation.
      reference_section_type: ABSTRACT
- term:
    id: GO:0005783
    label: endoplasmic reticulum
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  qualifier: located_in
  review:
    summary: Automated transfer of ER localization, consistent with experimental detection of NIX in the ER.
    action: KEEP_AS_NON_CORE
    reason: ER localization is documented but is a secondary site relative to the mitochondrial outer membrane.
    supported_by:
    - reference_id: PMID:10381623
      supporting_text: localizes in nuclear envelope, endoplasmic reticulum and mitochondria
      reference_section_type: ABSTRACT
- term:
    id: GO:0016020
    label: membrane
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  qualifier: located_in
  review:
    summary: NIX is a single-pass tail-anchored membrane protein, so generic membrane localization is correct but uninformative.
    action: MARK_AS_OVER_ANNOTATED
    reason: The generic membrane term is subsumed by the specific and well-supported mitochondrial outer membrane localization.
    supported_by:
    - reference_id: file:human/BNIP3L/BNIP3L-uniprot.txt
      supporting_text: Single-pass
      reference_section_type: DATABASE_ENTRY
- term:
    id: GO:0043065
    label: positive regulation of apoptotic process
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  qualifier: involved_in
  review:
    summary: Automated transfer of the pro-apoptotic process annotation; genuine but context-dependent and not the core function.
    action: KEEP_AS_NON_CORE
    reason: Cell-death promotion by NIX is contextual and direction-dependent; secondary to mitophagy.
    supported_by:
    - reference_id: PMID:9973195
      supporting_text: Overexpression of BNIP3alpha in transfected cells results in apoptosis and suppresses the antiapoptosis activity of E1B-19K and BCL-xL.
      reference_section_type: ABSTRACT
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:10381623
  qualifier: enables
  review:
    summary: Generic protein-binding annotation; the underlying B5 data describe specific self-association and BNIP3 heterodimerization, captured better by homodimerization activity.
    action: MARK_AS_OVER_ANNOTATED
    reason: Bare protein binding is uninformative; the specific interactions are represented by the identical protein binding / homodimerization annotations from this same study.
    supported_by:
    - reference_id: PMID:10381623
      supporting_text: B5 binds strongly to Nip3 and itself
      reference_section_type: ABSTRACT
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:16189514
  qualifier: enables
  review:
    summary: High-throughput interactome protein-binding annotation; uninformative for NIX function.
    action: MARK_AS_OVER_ANNOTATED
    reason: Generic protein binding from a proteome-scale interaction map does not identify an interpretable NIX function.
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:19060904
  qualifier: enables
  review:
    summary: High-throughput interactome protein-binding annotation; uninformative for NIX function.
    action: MARK_AS_OVER_ANNOTATED
    reason: Generic protein binding from a binary interactome dataset does not specify a meaningful function.
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:21516116
  qualifier: enables
  review:
    summary: High-throughput interactome protein-binding annotation; uninformative for NIX function.
    action: MARK_AS_OVER_ANNOTATED
    reason: Generic protein binding from an interactome-mapping method is not functionally specific.
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:22645275
  qualifier: enables
  review:
    summary: Generic protein-binding annotation from an ATP13A2/alpha-synuclein interactome study; uninformative for core NIX function.
    action: MARK_AS_OVER_ANNOTATED
    reason: Bare protein binding does not specify a NIX function; the interaction is not tied to core mitophagy biology.
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:24316735
  qualifier: enables
  review:
    summary: Generic protein-binding annotation from a TR3/NR4A1 autophagic-cell-death study; uninformative as bare protein binding.
    action: MARK_AS_OVER_ANNOTATED
    reason: The term protein binding is too general; the NR4A1 interaction is not informative as core NIX function.
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:24981860
  qualifier: enables
  review:
    summary: High-throughput chromatin-related interactome protein-binding annotation; uninformative for NIX function.
    action: MARK_AS_OVER_ANNOTATED
    reason: Generic protein binding from a large-scale interaction study does not specify a NIX function.
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:25416956
  qualifier: enables
  review:
    summary: High-throughput interactome protein-binding annotation; uninformative for NIX function.
    action: MARK_AS_OVER_ANNOTATED
    reason: Generic protein binding from a proteome-scale interactome map is not functionally specific.
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:25910212
  qualifier: enables
  review:
    summary: High-throughput interactome protein-binding annotation; uninformative for NIX function.
    action: MARK_AS_OVER_ANNOTATED
    reason: Generic protein binding from a disease-interactome perturbation study is not functionally specific.
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:27107012
  qualifier: enables
  review:
    summary: High-throughput interactome protein-binding annotation; uninformative for NIX function.
    action: MARK_AS_OVER_ANNOTATED
    reason: Generic protein binding from a pooled interaction screen does not specify a NIX function.
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:28514442
  qualifier: enables
  review:
    summary: High-throughput interactome protein-binding annotation; uninformative for NIX function.
    action: MARK_AS_OVER_ANNOTATED
    reason: Generic protein binding from a large-scale interactome study is not functionally specific.
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:31515488
  qualifier: enables
  review:
    summary: High-throughput interactome protein-binding annotation; uninformative for NIX function.
    action: MARK_AS_OVER_ANNOTATED
    reason: Generic protein binding from a variant-interaction study is not functionally specific.
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:32296183
  qualifier: enables
  review:
    summary: High-throughput interactome protein-binding annotation; uninformative for NIX function.
    action: MARK_AS_OVER_ANNOTATED
    reason: Generic protein binding from a reference binary interactome map is not functionally specific.
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:33961781
  qualifier: enables
  review:
    summary: High-throughput interactome protein-binding annotation; uninformative for NIX function.
    action: MARK_AS_OVER_ANNOTATED
    reason: Generic protein binding from a cell-specific interactome remodeling study is not functionally specific.
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:34845370
  qualifier: enables
  review:
    summary: This protein-binding annotation reflects the specific, functionally important interaction of NIX with SARS-CoV-2 ORF10 and LC3B during virus-hijacked mitophagy; as bare protein binding it is uninformative.
    action: MARK_AS_OVER_ANNOTATED
    reason: The underlying interaction is meaningful (ORF10/LC3B binding driving NIX-mediated mitophagy), but the generic protein binding term does not capture it; the antiviral mitophagy biology is curated under defense response to virus.
    supported_by:
    - reference_id: PMID:34845370
      supporting_text: ORF10 was translocated to mitochondria by interacting with the mitophagy receptor Nip3-like protein X (NIX) and induced mitophagy through its interaction with both NIX and LC3B
      reference_section_type: ABSTRACT
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:39526800
  qualifier: enables
  review:
    summary: High-throughput Legionella effector two-hybrid interactome protein-binding annotation; uninformative for NIX function.
    action: MARK_AS_OVER_ANNOTATED
    reason: Generic protein binding from a pathogen-effector interactome screen is not functionally specific for NIX.
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:9973195
  qualifier: enables
  review:
    summary: Generic protein-binding annotation; the underlying data describe specific interactions with E1B-19K, BCL-2 and BCL-xL, not informative as bare binding.
    action: MARK_AS_OVER_ANNOTATED
    reason: Bare protein binding is uninformative; the specific anti-apoptotic-protein interactions are better represented elsewhere.
    supported_by:
    - reference_id: PMID:9973195
      supporting_text: BNIP3alpha interacts with viral antiapoptosis protein E1B-19K and cellular antiapoptosis proteins BCL-2 and BCL-xL.
      reference_section_type: ABSTRACT
- term:
    id: GO:0042802
    label: identical protein binding
  evidence_type: IPI
  original_reference_id: PMID:10381623
  qualifier: enables
  review:
    summary: NIX/B5 self-associates, and the original study directly shows it binds itself; identical protein binding (self-association) is supported.
    action: ACCEPT
    reason: Self-association is directly demonstrated and is a genuine, informative molecular property of NIX.
    supported_by:
    - reference_id: PMID:10381623
      supporting_text: B5 binds strongly to Nip3 and itself
      reference_section_type: ABSTRACT
- term:
    id: GO:0042802
    label: identical protein binding
  evidence_type: IPI
  original_reference_id: PMID:16189514
  qualifier: enables
  review:
    summary: NIX self-association is recorded as identical protein binding in a high-throughput interactome (IntAct O60238-O60238); consistent with directly demonstrated self-association.
    action: ACCEPT
    reason: NIX self-association is independently supported by direct biochemistry; the high-throughput identical-protein-binding hit is consistent and informative.
    supported_by:
    - reference_id: PMID:10381623
      supporting_text: B5 binds strongly to Nip3 and itself
      reference_section_type: ABSTRACT
- term:
    id: GO:0042802
    label: identical protein binding
  evidence_type: IPI
  original_reference_id: PMID:21516116
  qualifier: enables
  review:
    summary: NIX self-association recorded as identical protein binding from interactome mapping; consistent with demonstrated self-association.
    action: ACCEPT
    reason: Consistent with directly demonstrated NIX self-association and informative as a homodimerization property.
    supported_by:
    - reference_id: PMID:10381623
      supporting_text: B5 binds strongly to Nip3 and itself
      reference_section_type: ABSTRACT
- term:
    id: GO:0042802
    label: identical protein binding
  evidence_type: IPI
  original_reference_id: PMID:25416956
  qualifier: enables
  review:
    summary: NIX self-association recorded as identical protein binding from a proteome-scale interactome; consistent with demonstrated self-association.
    action: ACCEPT
    reason: Consistent with directly demonstrated NIX self-association.
    supported_by:
    - reference_id: PMID:10381623
      supporting_text: B5 binds strongly to Nip3 and itself
      reference_section_type: ABSTRACT
- term:
    id: GO:0042802
    label: identical protein binding
  evidence_type: IPI
  original_reference_id: PMID:27107012
  qualifier: enables
  review:
    summary: NIX self-association recorded as identical protein binding from a pooled interaction screen; consistent with demonstrated self-association.
    action: ACCEPT
    reason: Consistent with directly demonstrated NIX self-association.
    supported_by:
    - reference_id: PMID:10381623
      supporting_text: B5 binds strongly to Nip3 and itself
      reference_section_type: ABSTRACT
- term:
    id: GO:0005739
    label: mitochondrion
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  qualifier: located_in
  review:
    summary: General mitochondrial localization; correct but less specific than the mitochondrial outer membrane localization.
    action: KEEP_AS_NON_CORE
    reason: Accurate but subsumed by the more precise mitochondrial outer membrane annotation.
    supported_by:
    - reference_id: PMID:9973195
      supporting_text: Like BNIP3, BNIP3alpha seems to be predominantly localized in mitochondria.
      reference_section_type: ABSTRACT
- term:
    id: GO:0010917
    label: negative regulation of mitochondrial membrane potential
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  qualifier: involved_in
  review:
    summary: NIX/BNIP3 can affect mitochondrial membrane potential/permeability (linked to necrosis and to depolarization-triggered mitophagy), a contextual mitochondrial effect.
    action: KEEP_AS_NON_CORE
    reason: Effects on membrane potential are documented but are a downstream/contextual aspect rather than the core mitophagy-receptor activity.
    supported_by:
    - reference_id: PMID:21264228
      supporting_text: related to necrosis through the regulation of mitochondrial permeability transition pore (MPTP)
      reference_section_type: INTRODUCTION
- term:
    id: GO:0035794
    label: positive regulation of mitochondrial membrane permeability
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  qualifier: involved_in
  review:
    summary: NIX/BNIP3 are linked to opening of the mitochondrial permeability transition pore and necrosis-related membrane permeabilization, a contextual function.
    action: KEEP_AS_NON_CORE
    reason: Supported as a contextual mitochondrial membrane effect; secondary to mitophagy-receptor activity.
    supported_by:
    - reference_id: PMID:21264228
      supporting_text: related to necrosis through the regulation of mitochondrial permeability transition pore (MPTP)
      reference_section_type: INTRODUCTION
- term:
    id: GO:0042802
    label: identical protein binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  qualifier: enables
  review:
    summary: Automated identical-protein-binding annotation, consistent with directly demonstrated NIX self-association.
    action: ACCEPT
    reason: Consistent with documented NIX self-association.
    supported_by:
    - reference_id: PMID:10381623
      supporting_text: B5 binds strongly to Nip3 and itself
      reference_section_type: ABSTRACT
- term:
    id: GO:1901524
    label: regulation of mitophagy
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  qualifier: involved_in
  review:
    summary: Regulation of mitophagy is a core process for NIX, which acts as a mitochondrial receptor connecting mitochondria to the autophagy machinery via LC3/GABARAP.
    action: ACCEPT
    reason: Mitophagy is the defining conserved function of NIX and is strongly supported.
    supported_by:
    - reference_id: PMID:20200478
      supporting_text: Nix is a mitochondrial receptor that can directly connect to one of the autophagic machinery components, the Atg8 homologs LC3 and GABARAP.
      reference_section_type: ABSTRACT
- term:
    id: GO:1903747
    label: regulation of protein localization to mitochondrion
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  qualifier: involved_in
  review:
    summary: NIX recruits autophagy machinery (LC3/GABARAP) to mitochondria; this can be viewed as regulating protein localization to the mitochondrion, but it is better represented by mitophagy receptor activity.
    action: KEEP_AS_NON_CORE
    reason: The annotation captures a mechanistic aspect (recruitment of Atg8-family proteins to mitochondria) of the core mitophagy function but as a broad regulatory term is less precise; retained as non-core.
    supported_by:
    - reference_id: PMID:20200478
      supporting_text: Nix is a mitochondrial receptor that can directly connect to one of the autophagic machinery components, the Atg8 homologs LC3 and GABARAP.
      reference_section_type: ABSTRACT
- term:
    id: GO:0005739
    label: mitochondrion
  evidence_type: IDA
  original_reference_id: GO_REF:0000052
  qualifier: located_in
  review:
    summary: Immunofluorescence-based mitochondrial localization, consistent with the predominant mitochondrial localization of NIX.
    action: KEEP_AS_NON_CORE
    reason: Accurate but subsumed by the more precise mitochondrial outer membrane localization.
    supported_by:
    - reference_id: PMID:9973195
      supporting_text: Like BNIP3, BNIP3alpha seems to be predominantly localized in mitochondria.
      reference_section_type: ABSTRACT
- term:
    id: GO:0016607
    label: nuclear speck
  evidence_type: IDA
  original_reference_id: GO_REF:0000052
  qualifier: located_in
  review:
    summary: A nuclear speck localization (HPA immunofluorescence) is weakly supported and inconsistent with the established tail-anchored mitochondrial outer membrane biology of NIX.
    action: MARK_AS_OVER_ANNOTATED
    reason: No defined nuclear-speck function exists for NIX; this single-source localization likely reflects antibody/overexpression artifact and is not the functional compartment.
- term:
    id: GO:0005739
    label: mitochondrion
  evidence_type: HTP
  original_reference_id: PMID:34800366
  qualifier: located_in
  review:
    summary: High-throughput mitochondrial proteome localization, consistent with NIX being a mitochondrial protein.
    action: KEEP_AS_NON_CORE
    reason: Accurate but subsumed by the more precise mitochondrial outer membrane localization.
    supported_by:
    - reference_id: PMID:34800366
      supporting_text: mitochondrial proteome
      reference_section_type: TITLE
- term:
    id: GO:0043069
    label: negative regulation of programmed cell death
  evidence_type: IGI
  original_reference_id: PMID:19273585
  qualifier: acts_upstream_of_or_within
  review:
    summary: Under hypoxia, HIF-induced BNIP3/BNIP3L promote pro-survival autophagy and their ablation triggers cell death, supporting a negative regulation of programmed cell death role in this context.
    action: KEEP_AS_NON_CORE
    reason: Supported by genetic evidence but contextual (hypoxia/survival); secondary to the core mitophagy-receptor function.
    supported_by:
    - reference_id: PMID:19273585
      supporting_text: the ablation of BNIP3 and/or BNIP3L triggers cell death
      reference_section_type: ABSTRACT
    - reference_id: PMID:19273585
      supporting_text: Hypoxia-induced autophagy via BNIP3 and BNIP3L is clearly a survival mechanism that promotes tumor progression.
      reference_section_type: ABSTRACT
- term:
    id: GO:0016239
    label: positive regulation of macroautophagy
  evidence_type: IGI
  original_reference_id: PMID:19273585
  qualifier: acts_upstream_of_or_within
  review:
    summary: BNIP3/BNIP3L are required for hypoxia-induced macroautophagy and their atypical BH3 domains can initiate autophagy by disrupting the Bcl-2-Beclin1 complex.
    action: ACCEPT
    reason: Positive regulation of macroautophagy is well supported by combined silencing/ectopic expression and BH3-peptide experiments, and is closely tied to the autophagy-receptor biology of NIX.
    supported_by:
    - reference_id: PMID:19273585
      supporting_text: the combined silencing of these two HIF targets suppresses hypoxia-mediated autophagy
      reference_section_type: ABSTRACT
    - reference_id: PMID:19273585
      supporting_text: the ectopic expression of both BNIP3 and BNIP3L in normoxia activates autophagy
      reference_section_type: ABSTRACT
- term:
    id: GO:0071456
    label: cellular response to hypoxia
  evidence_type: IGI
  original_reference_id: PMID:19273585
  qualifier: acts_upstream_of_or_within
  review:
    summary: BNIP3L is a HIF target that mediates hypoxia-induced autophagy, supporting a role in the cellular response to hypoxia.
    action: KEEP_AS_NON_CORE
    reason: Supported as part of the hypoxia/HIF-autophagy axis but is a contextual upstream process rather than the core molecular function.
    supported_by:
    - reference_id: PMID:19273585
      supporting_text: the combined silencing of these two HIF targets suppresses hypoxia-mediated autophagy
      reference_section_type: ABSTRACT
- term:
    id: GO:0005741
    label: mitochondrial outer membrane
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-6798004
  qualifier: located_in
  review:
    summary: Reactome-curated mitochondrial outer membrane localization (TP53 stimulates BNIP3L expression pathway).
    action: ACCEPT
    reason: Consistent with the well-supported core localization.
    supported_by:
    - reference_id: PMID:20200478
      supporting_text: Nix is a mitochondrial outer membrane protein that is required for mitochondrial clearance during erythrocyte maturation.
      reference_section_type: ABSTRACT
- term:
    id: GO:0005741
    label: mitochondrial outer membrane
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-6801195
  qualifier: located_in
  review:
    summary: Reactome-curated mitochondrial outer membrane localization (STEAP3 binds BNIP3L pathway).
    action: ACCEPT
    reason: Consistent with the well-supported core localization.
    supported_by:
    - reference_id: PMID:20200478
      supporting_text: Nix is a mitochondrial outer membrane protein that is required for mitochondrial clearance during erythrocyte maturation.
      reference_section_type: ABSTRACT
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:20200478
  qualifier: enables
  review:
    summary: This protein-binding annotation reflects the functionally central interaction of NIX with the Atg8 homologs LC3/GABARAP, but as bare protein binding it is uninformative.
    action: MARK_AS_OVER_ANNOTATED
    reason: The underlying LC3/GABARAP interaction is the molecular basis of NIX mitophagy-receptor activity; bare protein binding does not capture this and the function is curated under regulation of mitophagy.
    supported_by:
    - reference_id: PMID:20200478
      supporting_text: Nix is a mitochondrial receptor that can directly connect to one of the autophagic machinery components, the Atg8 homologs LC3 and GABARAP.
      reference_section_type: ABSTRACT
- term:
    id: GO:0043065
    label: positive regulation of apoptotic process
  evidence_type: IDA
  original_reference_id: PMID:9973195
  qualifier: involved_in
  review:
    summary: Overexpression of BNIP3alpha induced apoptosis in transfected cells, providing direct (if overexpression-based) evidence for a pro-apoptotic role.
    action: KEEP_AS_NON_CORE
    reason: Direct evidence supports a pro-apoptotic capacity, but it is context-dependent/overexpression-driven and secondary to the conserved mitophagy function.
    supported_by:
    - reference_id: PMID:9973195
      supporting_text: Overexpression of BNIP3alpha in transfected cells results in apoptosis and suppresses the antiapoptosis activity of E1B-19K and BCL-xL.
      reference_section_type: ABSTRACT
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:21264221
  qualifier: enables
  review:
    summary: Generic protein-binding annotation associated with the Mieap/MALM mitochondrial quality-control studies; uninformative as bare binding.
    action: MARK_AS_OVER_ANNOTATED
    reason: Bare protein binding is uninformative; the relevant NIX-SPATA18/Mieap interaction is curated via the mitochondrial protein catabolic process annotation.
- term:
    id: GO:0005741
    label: mitochondrial outer membrane
  evidence_type: IMP
  original_reference_id: PMID:21264228
  qualifier: located_in
  review:
    summary: NIX localizes to and acts at the mitochondrial outer membrane, where it interacts with Mieap via its BH3 domain; mutational/localization analysis supports this compartment.
    action: ACCEPT
    reason: Directly supported core localization.
    supported_by:
    - reference_id: PMID:21264228
      supporting_text: A mitochondrial outer membrane protein NIX interacted with Mieap in a ROS-dependent manner via the BH3 domain of NIX and the coiled-coil domain of Mieap.
      reference_section_type: ABSTRACT
- term:
    id: GO:0035694
    label: mitochondrial protein catabolic process
  evidence_type: IMP
  original_reference_id: PMID:21264228
  qualifier: involved_in
  review:
    summary: NIX is an essential mediator of MALM (Mieap-induced accumulation of lysosome-like organelles within mitochondria), a non-canonical process that degrades oxidized mitochondrial proteins; NIX deficiency impairs MALM.
    action: ACCEPT
    reason: Loss-of-function (NIX knockdown) directly impairs MALM, supporting NIX involvement in mitochondrial protein catabolism within the mitochondrial quality-control context.
    supported_by:
    - reference_id: PMID:21264228
      supporting_text: Deficiency of NIX also completely impaired MALM.
      reference_section_type: ABSTRACT
- term:
    id: GO:0005521
    label: lamin binding
  evidence_type: IPI
  original_reference_id: PMID:10381623
  qualifier: enables
  review:
    summary: Lamin binding derives from the original B5/nuclear-envelope study; it is a specific but secondary interaction not central to the mitophagy-receptor function.
    action: KEEP_AS_NON_CORE
    reason: Retained as a specific (non-generic) binding annotation, but it is contextual to the nuclear-envelope localization and not the core function.
    supported_by:
    - reference_id: PMID:10381623
      supporting_text: localizes in nuclear envelope, endoplasmic reticulum and mitochondria
      reference_section_type: ABSTRACT
- term:
    id: GO:0005521
    label: lamin binding
  evidence_type: IDA
  original_reference_id: PMID:10381623
  qualifier: enables
  review:
    summary: Direct-assay lamin binding from the original B5 study; specific but secondary.
    action: KEEP_AS_NON_CORE
    reason: Specific binding annotation tied to nuclear-envelope localization; not the core function.
    supported_by:
    - reference_id: PMID:10381623
      supporting_text: localizes in nuclear envelope, endoplasmic reticulum and mitochondria
      reference_section_type: ABSTRACT
- term:
    id: GO:0005635
    label: nuclear envelope
  evidence_type: IDA
  original_reference_id: PMID:10381623
  qualifier: located_in
  review:
    summary: Direct localization of B5/NIX to the nuclear envelope in the original study; secondary site.
    action: KEEP_AS_NON_CORE
    reason: Documented but secondary localization relative to the mitochondrial outer membrane.
    supported_by:
    - reference_id: PMID:10381623
      supporting_text: localizes in nuclear envelope, endoplasmic reticulum and mitochondria
      reference_section_type: ABSTRACT
- term:
    id: GO:0005739
    label: mitochondrion
  evidence_type: IDA
  original_reference_id: PMID:10381623
  qualifier: located_in
  review:
    summary: Direct mitochondrial localization in the original B5 study.
    action: KEEP_AS_NON_CORE
    reason: Accurate but subsumed by the more precise mitochondrial outer membrane localization.
    supported_by:
    - reference_id: PMID:10381623
      supporting_text: localizes in nuclear envelope, endoplasmic reticulum and mitochondria
      reference_section_type: ABSTRACT
- term:
    id: GO:0005783
    label: endoplasmic reticulum
  evidence_type: IDA
  original_reference_id: PMID:10381623
  qualifier: located_in
  review:
    summary: Direct ER localization in the original B5 study; secondary site.
    action: KEEP_AS_NON_CORE
    reason: Documented but secondary localization relative to the mitochondrial outer membrane.
    supported_by:
    - reference_id: PMID:10381623
      supporting_text: localizes in nuclear envelope, endoplasmic reticulum and mitochondria
      reference_section_type: ABSTRACT
- term:
    id: GO:0016020
    label: membrane
  evidence_type: TAS
  original_reference_id: PMID:10381623
  qualifier: located_in
  review:
    summary: NIX/B5 contains a C-terminal transmembrane region; generic membrane localization is correct but uninformative.
    action: MARK_AS_OVER_ANNOTATED
    reason: Subsumed by the specific mitochondrial outer membrane localization.
    supported_by:
    - reference_id: PMID:10381623
      supporting_text: contains the putative BH3 and transmembrane regions
      reference_section_type: ABSTRACT
- term:
    id: GO:0042803
    label: protein homodimerization activity
  evidence_type: IDA
  original_reference_id: PMID:10381623
  qualifier: enables
  review:
    summary: NIX/B5 self-associates (binds itself), supporting protein homodimerization activity as a genuine molecular property.
    action: ACCEPT
    reason: Directly demonstrated self-association; informative homodimerization activity.
    supported_by:
    - reference_id: PMID:10381623
      supporting_text: B5 binds strongly to Nip3 and itself
      reference_section_type: ABSTRACT
- term:
    id: GO:0043066
    label: negative regulation of apoptotic process
  evidence_type: IDA
  original_reference_id: PMID:10381623
  qualifier: involved_in
  review:
    summary: In the original B5 study, NIX did not itself induce apoptosis but inhibited Nip3(BNIP3)-induced apoptosis, supporting an anti-apoptotic capacity in this context.
    action: KEEP_AS_NON_CORE
    reason: This anti-apoptotic effect is genuine but direction- and context-dependent (the same protein can also promote death); secondary to mitophagy.
    supported_by:
    - reference_id: PMID:10381623
      supporting_text: B5 does not induce apoptosis, but inhibits apoptosis induced by Nip3
      reference_section_type: ABSTRACT
- term:
    id: GO:0005739
    label: mitochondrion
  evidence_type: IDA
  original_reference_id: PMID:9973195
  qualifier: located_in
  review:
    summary: Direct mitochondrial localization of BNIP3alpha/NIX.
    action: KEEP_AS_NON_CORE
    reason: Accurate but subsumed by the more precise mitochondrial outer membrane localization.
    supported_by:
    - reference_id: PMID:9973195
      supporting_text: Like BNIP3, BNIP3alpha seems to be predominantly localized in mitochondria.
      reference_section_type: ABSTRACT
- term:
    id: GO:0051607
    label: defense response to virus
  evidence_type: IDA
  original_reference_id: PMID:9973195
  qualifier: involved_in
  review:
    summary: The cited 1999 BNIP3alpha paper is about apoptosis/anti-apoptotic-protein interactions and does not provide direct evidence for defense response to virus; the genuine antiviral connection (NIX-mediated mitophagy degrading MAVS) is established by later work, but viruses hijack this for immune evasion rather than NIX acting in host antiviral defense.
    action: REMOVE
    reason: The original reference (PMID:9973195) was reviewed and is about apoptosis/anti-apoptotic-protein interactions; it provides no evidence for a defense-response-to-virus role (this is therefore a removal on reviewed evidence, not an UNDECIDED due to inaccessible literature). Later literature (PMID:34845370) shows NIX-mediated mitophagy is hijacked by SARS-CoV-2 ORF10 to degrade MAVS and suppress innate immunity, the opposite of host antiviral defense; KSHV vIRF-1 similarly co-opts NIX. The annotation is unlikely to be correct based on the combined evidence.
    supported_by:
    - reference_id: PMID:34845370
      supporting_text: ORF10 was translocated to mitochondria by interacting with the mitophagy receptor Nip3-like protein X (NIX) and induced mitophagy through its interaction with both NIX and LC3B
      reference_section_type: ABSTRACT
    - reference_id: PMID:34845370
      supporting_text: NIX-mediated mitophagy is responsible for the elimination of spontaneously aggregated MAVS
      reference_section_type: INTRODUCTION
    additional_reference_ids:
    - PMID:34845370
references:
- id: GO_REF:0000002
  title: Gene Ontology annotation through association of InterPro records with GO
    terms
  findings: []
- id: GO_REF:0000033
  title: Annotation inferences using phylogenetic trees
  findings: []
- id: GO_REF:0000044
  title: Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location
    vocabulary mapping, accompanied by conservative changes to GO terms applied by
    UniProt
  findings: []
- id: GO_REF:0000052
  title: Gene Ontology annotation based on curation of immunofluorescence data
  findings: []
- id: GO_REF:0000107
  title: Automatic transfer of experimentally verified manual GO annotation data to
    orthologs using Ensembl Compara
  findings: []
- id: GO_REF:0000120
  title: Combined Automated Annotation using Multiple IEA Methods
  findings: []
- id: PMID:10381623
  title: A novel adenovirus E1B19K-binding protein B5 inhibits apoptosis induced by
    Nip3 by forming a heterodimer through the C-terminal hydrophobic region.
  findings: []
- id: PMID:16189514
  title: Towards a proteome-scale map of the human protein-protein interaction network.
  findings: []
- id: PMID:19060904
  title: An empirical framework for binary interactome mapping.
  findings: []
- id: PMID:19273585
  title: Hypoxia-induced autophagy is mediated through hypoxia-inducible factor induction
    of BNIP3 and BNIP3L via their BH3 domains.
  findings: []
- id: PMID:20200478
  title: Nix, a receptor protein for mitophagy in mammals.
  findings: []
- id: PMID:21264221
  title: Possible existence of lysosome-like organella within mitochondria and its
    role in mitochondrial quality control.
  findings: []
- id: PMID:21264228
  title: Mieap, a p53-inducible protein, controls mitochondrial quality by repairing
    or eliminating unhealthy mitochondria.
  findings: []
- id: PMID:21516116
  title: Next-generation sequencing to generate interactome datasets.
  findings: []
- id: PMID:22645275
  title: Identification of novel ATP13A2 interactors and their role in α-synuclein
    misfolding and toxicity.
  findings: []
- id: PMID:24316735
  title: Orphan nuclear receptor TR3 acts in autophagic cell death via mitochondrial
    signaling pathway.
  findings: []
- id: PMID:24981860
  title: Human-chromatin-related protein interactions identify a demethylase complex
    required for chromosome segregation.
  findings: []
- id: PMID:25416956
  title: A proteome-scale map of the human interactome network.
  findings: []
- id: PMID:25910212
  title: Widespread macromolecular interaction perturbations in human genetic disorders.
  findings: []
- id: PMID:27107012
  title: Pooled-matrix protein interaction screens using Barcode Fusion Genetics.
  findings: []
- id: PMID:28514442
  title: Architecture of the human interactome defines protein communities and disease
    networks.
  findings: []
- id: PMID:31515488
  title: Extensive disruption of protein interactions by genetic variants across the
    allele frequency spectrum in human populations.
  findings: []
- id: PMID:32296183
  title: A reference map of the human binary protein interactome.
  findings: []
- id: PMID:33961781
  title: Dual proteome-scale networks reveal cell-specific remodeling of the human
    interactome.
  findings: []
- id: PMID:34800366
  title: Quantitative high-confidence human mitochondrial proteome and its dynamics
    in cellular context.
  findings: []
- id: PMID:36215693
  title: BNIP3L/NIX regulates both mitophagy and pexophagy.
  full_text_unavailable: true
  findings:
  - statement: NIX, anchored in the mitochondrial outer membrane, also independently localizes
      to peroxisomes and drives their selective autophagic clearance (pexophagy), and Nix-null
      mouse tissue has increased peroxisomal content, showing that NIX acts as a selective
      autophagy receptor for more than one organelle.
- id: PMID:37102372
  title: FBXL4 ubiquitin ligase deficiency promotes mitophagy by elevating NIX levels.
  full_text_unavailable: true
  findings:
  - statement: A CRISPR screen of human E3 ubiquitin ligases identified VHL and FBXL4 as the
      strongest negative regulators of basal mitophagy, both converging on the mitophagy
      receptors BNIP3 and BNIP3L/NIX; FBXL4 destabilizes NIX/BNIP3 directly while VHL acts by
      suppressing HIF-1alpha-mediated transcription, and depletion of NIX is sufficient to
      restore mitophagy levels.
- id: PMID:37161784
  title: FBXL4 suppresses mitophagy by restricting the accumulation of NIX and BNIP3 mitophagy
    receptors.
  full_text_unavailable: true
  findings:
  - statement: The SCF(FBXL4) ubiquitin ligase complex localizes to the mitochondrial outer
      membrane in unstressed cells and constitutively ubiquitylates and degrades the mitophagy
      receptors NIX and BNIP3 to suppress basal mitophagy; pathogenic FBXL4 variants causing
      mtDNA depletion syndrome (MTDPS13) fail to mediate this turnover, linking dysregulated NIX
      accumulation to excessive basal mitophagy.
- id: PMID:37621214
  title: Nix interacts with WIPI2 to induce mitophagy.
  full_text_unavailable: true
  findings:
  - statement: In addition to its LIR motif that binds ATG8 proteins, NIX contains a minimal
      essential region (MER) that binds and recruits the autophagy effector WIPI2 to
      mitochondria; both the MER and the LIR are required for robust mitophagy, with the LIR
      reorganizing WIPI2 into puncta even in the absence of ATG8 proteins.
- id: PMID:38991726
  title: Dual-localized PPTC7 limits mitophagy through proximal and dynamic interactions with
    BNIP3 and NIX.
  full_text_unavailable: true
  findings:
  - statement: A pool of the mitochondrial phosphatase PPTC7 localizes to the outer mitochondrial
      membrane, dynamically associates with BNIP3 and NIX, and promotes their proteasomal
      turnover to limit basal mitophagy, acting post-transcriptionally and independently of
      HIF-1alpha stabilization.
- id: PMID:38992176
  title: 'PPTC7 antagonizes mitophagy by promoting BNIP3 and NIX degradation via SCF(FBXL4).'
  full_text_unavailable: true
  findings:
  - statement: PPTC7 is an essential cofactor for SCF(FBXL4)-mediated degradation of the BNIP3
      and NIX mitophagy receptors, acting as an outer-mitochondrial-membrane adaptor that links
      BNIP3/NIX to FBXL4 to suppress both steady-state and induced mitophagy, with the turnover
      function independent of PPTC7 phosphatase activity.
- id: PMID:34845370
  title: SARS-CoV-2 ORF10 suppresses the antiviral innate immune response by degrading
    MAVS through mitophagy.
  findings: []
- id: PMID:39526800
  title: A comprehensive two-hybrid analysis to explore the Legionella pneumophila
    effector-effector interactome.
  findings: []
- id: PMID:9973195
  title: 'BNIP3alpha: a human homolog of mitochondrial proapoptotic protein BNIP3.'
  findings: []
- id: Reactome:R-HSA-6798004
  title: TP53 stimulates BNIP3L expression
  findings: []
- id: Reactome:R-HSA-6801195
  title: STEAP3 binds BNIP3L
  findings: []
- id: file:human/BNIP3L/BNIP3L-uniprot.txt
  title: BNIP3L (NIX) UniProtKB record O60238
  findings: []
- id: file:human/BNIP3L/BNIP3L-notes.md
  title: Manual BNIP3L curation notes
  findings: []
core_functions:
- description: BNIP3L/NIX functions as a mitophagy receptor at the mitochondrial outer membrane. Anchored by its C-terminal transmembrane helix with an N-terminal cytosolic region containing an LC3-interacting region, it directly binds Atg8-family proteins (LC3 and GABARAP) to tether mitochondria to the forming autophagosome, driving selective autophagic clearance of mitochondria. This is essential for mitochondrial elimination during terminal erythroid/reticulocyte maturation and contributes to developmentally programmed and stress-induced mitochondrial turnover.
  directly_involved_in:
  - id: GO:1901524
    label: regulation of mitophagy
  - id: GO:0016239
    label: positive regulation of macroautophagy
  locations:
  - id: GO:0005741
    label: mitochondrial outer membrane
  supported_by:
  - reference_id: PMID:20200478
    supporting_text: Nix is a mitochondrial receptor that can directly connect to one of the autophagic machinery components, the Atg8 homologs LC3 and GABARAP.
    reference_section_type: ABSTRACT
  - reference_id: PMID:20200478
    supporting_text: Nix is a mitochondrial outer membrane protein that is required for mitochondrial clearance during erythrocyte maturation.
    reference_section_type: ABSTRACT
- description: Under hypoxia, NIX (a HIF target) promotes pro-survival macroautophagy. Its atypical BH3 domain can disrupt the Bcl-2-Beclin1 complex to initiate autophagy without inducing cell death, and combined loss of BNIP3 and BNIP3L suppresses hypoxia-induced autophagy.
  directly_involved_in:
  - id: GO:0016239
    label: positive regulation of macroautophagy
  - id: GO:0071456
    label: cellular response to hypoxia
  locations:
  - id: GO:0005741
    label: mitochondrial outer membrane
  supported_by:
  - reference_id: PMID:19273585
    supporting_text: the atypical BH3 domains of hypoxia-induced BNIP3/BNIP3L have
    reference_section_type: ABSTRACT
  - reference_id: PMID:19273585
    supporting_text: the ectopic expression of both BNIP3 and BNIP3L in normoxia activates autophagy
    reference_section_type: ABSTRACT
- description: NIX participates in non-canonical mitochondrial quality control via ROS-dependent interaction with SPATA18/MIEAP, acting as an essential mediator of MALM that degrades oxidized mitochondrial proteins; NIX deficiency abolishes MALM.
  directly_involved_in:
  - id: GO:0035694
    label: mitochondrial protein catabolic process
  locations:
  - id: GO:0005741
    label: mitochondrial outer membrane
  supported_by:
  - reference_id: PMID:21264228
    supporting_text: A mitochondrial outer membrane protein NIX interacted with Mieap in a ROS-dependent manner via the BH3 domain of NIX and the coiled-coil domain of Mieap.
    reference_section_type: ABSTRACT
  - reference_id: PMID:21264228
    supporting_text: Deficiency of NIX also completely impaired MALM.
    reference_section_type: ABSTRACT
proposed_new_terms:
- proposed_name: mitophagy receptor activity
  proposed_definition: A protein-tethering activity in which a mitochondrial outer membrane protein bridges the mitochondrion to an Atg8-family protein (LC3/GABARAP) via an LC3-interacting region (LIR), thereby targeting the mitochondrion for selective autophagic degradation (mitophagy).
  justification: NIX/BNIP3L's defining molecular activity is acting as a selective autophagy (mitophagy) receptor that bridges the mitochondrial outer membrane to Atg8-family proteins (LC3/GABARAP) via its LIR motif. No existing molecular-function term in the seeded annotation set captures this cargo-receptor activity; the closest existing term used is protein homodimerization activity, which is incomplete.
  supported_by:
  - reference_id: PMID:20200478
    supporting_text: Nix is a mitochondrial receptor that can directly connect to one of the autophagic machinery components, the Atg8 homologs LC3 and GABARAP.
    reference_section_type: ABSTRACT
suggested_questions:
- question: Does human NIX have a genuine host-protective antiviral function, or is NIX-mediated mitophagy primarily a target that diverse viruses hijack (e.g., SARS-CoV-2 ORF10, KSHV vIRF-1) to degrade MAVS and evade innate immunity?
  experts:
  - He H
  - Choi YB
- question: How is the balance between NIX-driven pro-survival mitophagy and NIX-associated cell death (necrosis/membrane permeabilization) controlled in a given cell type and stress context?
  experts:
  - Mazure NM
  - Dorn GW
- question: To what extent is NIX-mediated pexophagy a distinct cargo-selection program versus a by-product of shared upstream (iron-chelation/HIF) signaling, and is the peroxisomal pool of NIX targeted or regulated differently from the mitochondrial pool?
  experts:
  - Ganley IG
  - Boya P
- question: Is the FBXL4/PPTC7-mediated constitutive turnover of NIX a general rheostat for basal mitophagy across tissues, and does failure of this turnover (e.g., FBXL4 variants) cause disease specifically through NIX rather than BNIP3 accumulation?
  experts:
  - Pagan JK
  - Niemi NM
suggested_experiments:
- hypothesis: NIX functions as an LIR-dependent mitophagy receptor whose Atg8-family binding is required for programmed mitochondrial clearance.
  description: Compare wild-type NIX with LIR-motif point mutants (abolishing LC3/GABARAP binding) for their ability to rescue mitochondrial clearance during reticulocyte maturation and stress-induced mitophagy in NIX-null cells, using flow cytometry of mitochondrial mass and mito-Keima/mito-QC reporters.
  experiment_type: structure-function rescue and mitophagy flux assay
- hypothesis: NIX-mediated mitophagy is required for MAVS turnover and shapes innate antiviral signaling.
  description: Knock out NIX in cells and measure MAVS levels, type I interferon induction, and viral replication with and without virus-encoded mitophagy inducers (e.g., ORF10), distinguishing host-protective versus virus-exploited roles.
  experiment_type: loss-of-function antiviral signaling assay
- hypothesis: NIX acts as a selective autophagy receptor for peroxisomes (pexophagy) in addition to mitochondria, using a peroxisome-localized pool distinct from its mitochondrial pool.
  description: In NIX-null cells reconstituted with wild-type versus LIR-mutant NIX, quantify pexophagy flux (pexo-QC/pexophagy reporters and peroxisomal marker PMP70 loss) under iron chelation and during cardiomyocyte/erythroid differentiation, and use organelle fractionation plus targeted (peroxisome- vs mitochondria-restricted) NIX constructs to test whether peroxisomal cargo selection is separable from mitochondrial mitophagy.
  experiment_type: structure-function rescue and selective-autophagy flux assay