BAG3

Existing Annotations Review

GO Term	Evidence	Action	Reason
GO:0005634 nucleus	IBA GO_REF:0000033	KEEP AS NON CORE	Summary: BAG3 can enter or colocalize with the nucleus under heat stress through its HSF1-related shuttling role. Reason: Nuclear localization is experimentally supported, but it is condition-dependent and not the primary BAG3 proteostasis function. Supporting Evidence: PMID:26159920 BAG3 rapidly translocalized to the nucleus upon heat stress.
GO:0005829 cytosol	IBA GO_REF:0000033	ACCEPT	Summary: BAG3 carries out its major HSP70 co-chaperone and CASA functions in the cytosol. Reason: The cytosol is the main site for HSP70/sHSP complex formation and BAG3-mediated aggresome targeting. Supporting Evidence: file:human/BAG3/BAG3-deep-research-falcon.md See deep research file for comprehensive analysis
GO:0016020 membrane	IBA GO_REF:0000033	REMOVE	Summary: The inherited membrane annotation is not supported as a primary BAG3 localization. Reason: BAG3 is a soluble co-chaperone/adaptor; the reviewed evidence supports cytosol, nucleus under heat stress, aggresome/autophagy structures, and Z-disc, not membrane residence. Supporting Evidence: PMID:21252941 BAG3 localized to juxtanuclear inclusions that were also enriched in ubiquitinated proteins and vimentin PMID:26159920 BAG3 rapidly translocalized to the nucleus upon heat stress.
GO:0000774 adenyl-nucleotide exchange factor activity	IBA GO_REF:0000033	ACCEPT	Summary: BAG3 has HSP70 nucleotide-exchange factor activity through its BAG domain. Reason: Direct biochemical studies and UniProt describe BAG3 as an HSP70-family NEF that promotes ADP release/client release. Supporting Evidence: PMID:24318877 Proteins with Bcl2-associated anthanogene (BAG) domains act as nucleotide exchange factors (NEFs) for the molecular chaperone heat shock protein 70 (Hsp70).
GO:0010664 negative regulation of striated muscle cell apoptotic process	IBA GO_REF:0000033	KEEP AS NON CORE	Summary: The striated-muscle anti-apoptotic annotation is plausible but secondary to BAG3 proteostasis and muscle-maintenance roles. Reason: BAG3 mutations cause muscle and cardiac disease and BAG3 has anti-apoptotic activity, but the core evidence points to CASA/Z-disc proteostasis rather than a direct striated-muscle apoptosis program. Supporting Evidence: PMID:10597216 Bis itself exerted only weak anti-apoptotic activity, but was synergistic with Bcl-2 in preventing Bax-induced and Fas-mediated apoptosis. PMID:20060297 Stv and its mammalian ortholog BAG-3 coordinate the activity of Hsc70 and the small heat shock protein HspB8 during disposal that is initiated by the chaperone-associated ubiquitin ligase CHIP and the autophagic ubiquitin adaptor p62.
GO:0046716 muscle cell cellular homeostasis	IBA GO_REF:0000033	ACCEPT	Summary: BAG3 supports muscle cell homeostasis through CASA-mediated Z-disc and sarcomere proteostasis. Reason: The CASA machinery is required for Z-disk maintenance and muscle integrity, making this an appropriate higher-level core process in muscle. Supporting Evidence: PMID:20060297 Stv and its mammalian ortholog BAG-3 coordinate the activity of Hsc70 and the small heat shock protein HspB8 during disposal that is initiated by the chaperone-associated ubiquitin ligase CHIP and the autophagic ubiquitin adaptor p62.
GO:0050821 protein stabilization	IBA GO_REF:0000033	MARK AS OVER ANNOTATED	Summary: Protein stabilization is related to BAG3 proteostasis but is less precise than documented chaperone-adaptor and aggrephagy functions. Reason: BAG3 can stabilize chaperone clients or complexes in some contexts, but often promotes disposal of damaged proteins; the annotation is too broad to treat as a core BAG3 function. Supporting Evidence: PMID:18006506 Bag3 overexpression resulted in the accelerated degradation of Htt43Q, whereas Bag3 knockdown prevented HspB8-induced Htt43Q degradation. PMID:27884606 We report that the Hsp70 co-chaperone, BAG3, is a modular, scaffolding factor to bring together sHsps and Hsp70s.
GO:0051087 protein-folding chaperone binding	IBA GO_REF:0000033	ACCEPT	Summary: BAG3 binds protein-folding chaperones including HSP70/HSC70 and small heat shock proteins such as HSPB8. Reason: Chaperone binding is a central molecular feature of BAG3 and underlies the CASA complex. Supporting Evidence: PMID:27884606 We report that the Hsp70 co-chaperone, BAG3, is a modular, scaffolding factor to bring together sHsps and Hsp70s.
GO:0000045 autophagosome assembly	IEA GO_REF:0000107	ACCEPT	Summary: BAG3 participates in autophagosome formation during CASA, particularly through SYNPO2-dependent assembly in mechanotransduction. Reason: The term is broad, but the literature supports BAG3-dependent autophagosome formation as part of CASA. Supporting Evidence: PMID:23434281 The CASA complex, comprised of the molecular chaperones Hsc70 and HspB8 and the cochaperone BAG3, senses the mechanical unfolding of the actin-crosslinking protein filamin.
GO:0001725 stress fiber	IEA GO_REF:0000107	MARK AS OVER ANNOTATED	Summary: Stress-fiber localization is a weak inference from cytoskeletal BAG3 biology. Reason: BAG3 clearly participates in actin/Z-disc mechanotransduction, but the reviewed evidence more strongly supports Z-disc and CASA complexes than stress fiber localization. Supporting Evidence: PMID:23434281 The CASA complex, comprised of the molecular chaperones Hsc70 and HspB8 and the cochaperone BAG3, senses the mechanical unfolding of the actin-crosslinking protein filamin.
GO:0021510 spinal cord development	IEA GO_REF:0000107	REMOVE	Summary: Spinal cord development is not supported as a direct BAG3 gene function. Reason: BAG3 is detected in spinal cord motor neurons and ALS model inclusions under proteotoxic stress, supporting neuronal proteostasis/aggresome biology rather than normal spinal cord development. Supporting Evidence: PMID:21252941 surviving spinal cord motor neurons were detected showing SOD1- and BAG3-positive perinuclear inclusions of different sizes
GO:0030018 Z disc	IEA GO_REF:0000107	ACCEPT	Summary: BAG3 is supported at the Z disc in striated muscle where CASA preserves sarcomeric architecture. Reason: Z-disc maintenance is a major tissue context for BAG3 function and is directly tied to CASA-mediated disposal of damaged components. Supporting Evidence: PMID:20060297 Stv and its mammalian ortholog BAG-3 coordinate the activity of Hsc70 and the small heat shock protein HspB8 during disposal that is initiated by the chaperone-associated ubiquitin ligase CHIP and the autophagic ubiquitin adaptor p62.
GO:0043066 negative regulation of apoptotic process	IEA GO_REF:0000107	KEEP AS NON CORE	Summary: BAG3 has anti-apoptotic effects, but apoptosis regulation is not its primary conserved molecular role. Reason: The BCL2 interaction supports a non-core anti-apoptotic role; the dominant functional synthesis is co-chaperone/CASA proteostasis. Supporting Evidence: PMID:10597216 Bis itself exerted only weak anti-apoptotic activity, but was synergistic with Bcl-2 in preventing Bax-induced and Fas-mediated apoptosis.
GO:0044877 protein-containing complex binding	IEA GO_REF:0000120	MODIFY	Summary: Protein-containing complex binding is too generic for BAG3. Reason: The evidence supports a more informative role as a protein-macromolecule adaptor that links HSP70 to small heat shock proteins and CASA machinery. Proposed replacements: protein-macromolecule adaptor activity protein-folding chaperone binding Supporting Evidence: PMID:27884606 We report that the Hsp70 co-chaperone, BAG3, is a modular, scaffolding factor to bring together sHsps and Hsp70s.
GO:0046716 muscle cell cellular homeostasis	IEA GO_REF:0000120	ACCEPT	Summary: BAG3 supports muscle cell homeostasis through CASA-mediated maintenance of mechanically stressed muscle structures. Reason: This duplicate automated annotation is supported, although the underlying mechanism should be understood as CASA/Z-disc proteostasis. Supporting Evidence: PMID:20060297 Stv and its mammalian ortholog BAG-3 coordinate the activity of Hsc70 and the small heat shock protein HspB8 during disposal that is initiated by the chaperone-associated ubiquitin ligase CHIP and the autophagic ubiquitin adaptor p62. PMID:23434281 The CASA complex, comprised of the molecular chaperones Hsc70 and HspB8 and the cochaperone BAG3, senses the mechanical unfolding of the actin-crosslinking protein filamin.
GO:0061684 chaperone-mediated autophagy	IEA GO_REF:0000107	MODIFY	Summary: This term conflates CASA with canonical chaperone-mediated autophagy. Reason: BAG3 mediates chaperone-assisted selective autophagy/aggrephagy, which the primary CASA paper explicitly distinguishes from chaperone-mediated autophagy; GO:1905337 is the closest current GO term for BAG3-dependent CASA/aggrephagy pending a dedicated CASA process term. Proposed replacements: positive regulation of aggrephagy Supporting Evidence: PMID:20060297 CASA is thus distinct from chaperone-mediated autophagy, previously shown to facilitate the ubiquitin-independent, direct translocation of a client across the lysosomal membrane
GO:1903748 negative regulation of protein localization to mitochondrion	IEA GO_REF:0000107	REMOVE	Summary: A direct role in blocking protein localization to mitochondria is not supported by the BAG3 functional synthesis. Reason: BAG3 has anti-apoptotic and proteostasis roles, but this automated term appears to infer a downstream apoptosis-related effect rather than a direct BAG3 process; no primary evidence here supports direct BAG3 regulation of mitochondrial protein import or localization. Supporting Evidence: PMID:10597216 Bis itself exerted only weak anti-apoptotic activity, but was synergistic with Bcl-2 in preventing Bax-induced and Fas-mediated apoptosis.
GO:0005515 protein binding	IPI PMID:16189514 Towards a proteome-scale map of the human protein-protein in...	MARK AS OVER ANNOTATED	Summary: The annotation records a physical interaction but uses the uninformative generic term protein binding. Reason: BAG3 has many interaction partners, but GO curation should prefer specific terms such as chaperone binding, adaptor activity, dynein binding, or pathway annotations when supported; high-throughput protein-binding alone is not a useful functional annotation. Supporting Evidence: file:human/BAG3/BAG3-deep-research-falcon.md See deep research file for comprehensive analysis
GO:0005515 protein binding	IPI PMID:19229298 Protein quality control during aging involves recruitment of...	MARK AS OVER ANNOTATED	Summary: The annotation records a physical interaction but uses the uninformative generic term protein binding. Reason: BAG3 has many interaction partners, but GO curation should prefer specific terms such as chaperone binding, adaptor activity, dynein binding, or pathway annotations when supported; high-throughput protein-binding alone is not a useful functional annotation. Supporting Evidence: file:human/BAG3/BAG3-deep-research-falcon.md See deep research file for comprehensive analysis
GO:0005515 protein binding	IPI PMID:21044950 Genome-wide YFP fluorescence complementation screen identifi...	MARK AS OVER ANNOTATED	Summary: The annotation records a physical interaction but uses the uninformative generic term protein binding. Reason: BAG3 has many interaction partners, but GO curation should prefer specific terms such as chaperone binding, adaptor activity, dynein binding, or pathway annotations when supported; high-throughput protein-binding alone is not a useful functional annotation. Supporting Evidence: file:human/BAG3/BAG3-deep-research-falcon.md See deep research file for comprehensive analysis
GO:0005515 protein binding	IPI PMID:21516116 Next-generation sequencing to generate interactome datasets.	MARK AS OVER ANNOTATED	Summary: The annotation records a physical interaction but uses the uninformative generic term protein binding. Reason: BAG3 has many interaction partners, but GO curation should prefer specific terms such as chaperone binding, adaptor activity, dynein binding, or pathway annotations when supported; high-throughput protein-binding alone is not a useful functional annotation. Supporting Evidence: file:human/BAG3/BAG3-deep-research-falcon.md See deep research file for comprehensive analysis
GO:0005515 protein binding	IPI PMID:24510904 Unbiased screen for interactors of leucine-rich repeat kinas...	MARK AS OVER ANNOTATED	Summary: The annotation records a physical interaction but uses the uninformative generic term protein binding. Reason: BAG3 has many interaction partners, but GO curation should prefer specific terms such as chaperone binding, adaptor activity, dynein binding, or pathway annotations when supported; high-throughput protein-binding alone is not a useful functional annotation. Supporting Evidence: file:human/BAG3/BAG3-deep-research-falcon.md See deep research file for comprehensive analysis
GO:0005515 protein binding	IPI PMID:25036637 A quantitative chaperone interaction network reveals the arc...	MARK AS OVER ANNOTATED	Summary: The annotation records a physical interaction but uses the uninformative generic term protein binding. Reason: BAG3 has many interaction partners, but GO curation should prefer specific terms such as chaperone binding, adaptor activity, dynein binding, or pathway annotations when supported; high-throughput protein-binding alone is not a useful functional annotation. Supporting Evidence: file:human/BAG3/BAG3-deep-research-falcon.md See deep research file for comprehensive analysis
GO:0005515 protein binding	IPI PMID:25277244 The functional landscape of Hsp27 reveals new cellular proce...	MARK AS OVER ANNOTATED	Summary: The annotation records a physical interaction but uses the uninformative generic term protein binding. Reason: BAG3 has many interaction partners, but GO curation should prefer specific terms such as chaperone binding, adaptor activity, dynein binding, or pathway annotations when supported; high-throughput protein-binding alone is not a useful functional annotation. Supporting Evidence: file:human/BAG3/BAG3-deep-research-falcon.md See deep research file for comprehensive analysis
GO:0005515 protein binding	IPI PMID:25416956 A proteome-scale map of the human interactome network.	MARK AS OVER ANNOTATED	Summary: The annotation records a physical interaction but uses the uninformative generic term protein binding. Reason: BAG3 has many interaction partners, but GO curation should prefer specific terms such as chaperone binding, adaptor activity, dynein binding, or pathway annotations when supported; high-throughput protein-binding alone is not a useful functional annotation. Supporting Evidence: file:human/BAG3/BAG3-deep-research-falcon.md See deep research file for comprehensive analysis
GO:0005515 protein binding	IPI PMID:26496610 A human interactome in three quantitative dimensions organiz...	MARK AS OVER ANNOTATED	Summary: The annotation records a physical interaction but uses the uninformative generic term protein binding. Reason: BAG3 has many interaction partners, but GO curation should prefer specific terms such as chaperone binding, adaptor activity, dynein binding, or pathway annotations when supported; high-throughput protein-binding alone is not a useful functional annotation. Supporting Evidence: file:human/BAG3/BAG3-deep-research-falcon.md See deep research file for comprehensive analysis
GO:0005515 protein binding	IPI PMID:27880917 Phenotypic and Interaction Profiling of the Human Phosphatas...	MARK AS OVER ANNOTATED	Summary: The annotation records a physical interaction but uses the uninformative generic term protein binding. Reason: BAG3 has many interaction partners, but GO curation should prefer specific terms such as chaperone binding, adaptor activity, dynein binding, or pathway annotations when supported; high-throughput protein-binding alone is not a useful functional annotation. Supporting Evidence: file:human/BAG3/BAG3-deep-research-falcon.md See deep research file for comprehensive analysis
GO:0005515 protein binding	IPI PMID:28514442 Architecture of the human interactome defines protein commun...	MARK AS OVER ANNOTATED	Summary: The annotation records a physical interaction but uses the uninformative generic term protein binding. Reason: BAG3 has many interaction partners, but GO curation should prefer specific terms such as chaperone binding, adaptor activity, dynein binding, or pathway annotations when supported; high-throughput protein-binding alone is not a useful functional annotation. Supporting Evidence: file:human/BAG3/BAG3-deep-research-falcon.md See deep research file for comprehensive analysis
GO:0005515 protein binding	IPI PMID:31515488 Extensive disruption of protein interactions by genetic vari...	MARK AS OVER ANNOTATED	Summary: The annotation records a physical interaction but uses the uninformative generic term protein binding. Reason: BAG3 has many interaction partners, but GO curation should prefer specific terms such as chaperone binding, adaptor activity, dynein binding, or pathway annotations when supported; high-throughput protein-binding alone is not a useful functional annotation. Supporting Evidence: file:human/BAG3/BAG3-deep-research-falcon.md See deep research file for comprehensive analysis
GO:0005515 protein binding	IPI PMID:32296183 A reference map of the human binary protein interactome.	MARK AS OVER ANNOTATED	Summary: The annotation records a physical interaction but uses the uninformative generic term protein binding. Reason: BAG3 has many interaction partners, but GO curation should prefer specific terms such as chaperone binding, adaptor activity, dynein binding, or pathway annotations when supported; high-throughput protein-binding alone is not a useful functional annotation. Supporting Evidence: file:human/BAG3/BAG3-deep-research-falcon.md See deep research file for comprehensive analysis
GO:0005515 protein binding	IPI PMID:32707033 Kinase Interaction Network Expands Functional and Disease Ro...	MARK AS OVER ANNOTATED	Summary: The annotation records a physical interaction but uses the uninformative generic term protein binding. Reason: BAG3 has many interaction partners, but GO curation should prefer specific terms such as chaperone binding, adaptor activity, dynein binding, or pathway annotations when supported; high-throughput protein-binding alone is not a useful functional annotation. Supporting Evidence: file:human/BAG3/BAG3-deep-research-falcon.md See deep research file for comprehensive analysis
GO:0005515 protein binding	IPI PMID:32814053 Interactome Mapping Provides a Network of Neurodegenerative ...	MARK AS OVER ANNOTATED	Summary: The annotation records a physical interaction but uses the uninformative generic term protein binding. Reason: BAG3 has many interaction partners, but GO curation should prefer specific terms such as chaperone binding, adaptor activity, dynein binding, or pathway annotations when supported; high-throughput protein-binding alone is not a useful functional annotation. Supporting Evidence: file:human/BAG3/BAG3-deep-research-falcon.md See deep research file for comprehensive analysis
GO:0005515 protein binding	IPI PMID:33961781 Dual proteome-scale networks reveal cell-specific remodeling...	MARK AS OVER ANNOTATED	Summary: The annotation records a physical interaction but uses the uninformative generic term protein binding. Reason: BAG3 has many interaction partners, but GO curation should prefer specific terms such as chaperone binding, adaptor activity, dynein binding, or pathway annotations when supported; high-throughput protein-binding alone is not a useful functional annotation. Supporting Evidence: file:human/BAG3/BAG3-deep-research-falcon.md See deep research file for comprehensive analysis
GO:0005634 nucleus	IEA GO_REF:0000044	KEEP AS NON CORE	Summary: UniProt-based nuclear localization is supported under heat stress and HSF1 shuttling contexts. Reason: BAG3 can translocate to or colocalize in the nucleus on heat stress, but this is condition-dependent. Supporting Evidence: PMID:26159920 BAG3 rapidly translocalized to the nucleus upon heat stress.
GO:0005737 cytoplasm	IEA GO_REF:0000120	ACCEPT	Summary: UniProt-based cytoplasmic localization matches the main BAG3 co-chaperone and CASA context. Reason: BAG3 is predominantly cytoplasmic/cytosolic and acts there in HSP70/sHSP complexes. Supporting Evidence: file:human/BAG3/BAG3-deep-research-falcon.md See deep research file for comprehensive analysis
GO:0006457 protein folding	IEA GO_REF:0000117	ACCEPT	Summary: BAG3 participates in protein folding proteostasis through its HSP70 NEF and chaperone-scaffold functions. Reason: Although broad, protein folding reflects BAG3 core activity in HSP70/sHSP chaperone cycles; more specific molecular annotations capture the mechanism. Supporting Evidence: PMID:24318877 Proteins with Bcl2-associated anthanogene (BAG) domains act as nucleotide exchange factors (NEFs) for the molecular chaperone heat shock protein 70 (Hsp70). PMID:27884606 We report that the Hsp70 co-chaperone, BAG3, is a modular, scaffolding factor to bring together sHsps and Hsp70s.
GO:0010664 negative regulation of striated muscle cell apoptotic process	IEA GO_REF:0000117	KEEP AS NON CORE	Summary: The striated-muscle anti-apoptotic process annotation is secondary and over-specific. Reason: The stronger muscle evidence supports CASA/Z-disc homeostasis; anti-apoptotic activity is supported, but not as a striated-muscle-specific core process. Supporting Evidence: PMID:20060297 Stv and its mammalian ortholog BAG-3 coordinate the activity of Hsc70 and the small heat shock protein HspB8 during disposal that is initiated by the chaperone-associated ubiquitin ligase CHIP and the autophagic ubiquitin adaptor p62. PMID:10597216 Bis itself exerted only weak anti-apoptotic activity, but was synergistic with Bcl-2 in preventing Bax-induced and Fas-mediated apoptosis.
GO:0050821 protein stabilization	IEA GO_REF:0000117	MARK AS OVER ANNOTATED	Summary: Protein stabilization is related to BAG3 proteostasis but is less precise than documented chaperone-adaptor and aggrephagy functions. Reason: BAG3 can stabilize chaperone clients or complexes in some contexts, but often promotes disposal of damaged proteins; the annotation is too broad to treat as a core BAG3 function. Supporting Evidence: PMID:18006506 Bag3 overexpression resulted in the accelerated degradation of Htt43Q, whereas Bag3 knockdown prevented HspB8-induced Htt43Q degradation. PMID:27884606 We report that the Hsp70 co-chaperone, BAG3, is a modular, scaffolding factor to bring together sHsps and Hsp70s.
GO:0051087 protein-folding chaperone binding	IEA GO_REF:0000002	ACCEPT	Summary: Protein-folding chaperone binding is supported by InterPro/domain logic and experimental work. Reason: The BAG domain and IPV motifs bind HSP70/HSC70 and small heat shock proteins, respectively. Supporting Evidence: PMID:27884606 We report that the Hsp70 co-chaperone, BAG3, is a modular, scaffolding factor to bring together sHsps and Hsp70s.
GO:0097191 extrinsic apoptotic signaling pathway	IEA GO_REF:0000117	KEEP AS NON CORE	Summary: BAG3 has reported anti-apoptotic effects, but the broad extrinsic apoptotic signaling annotation is non-core. Reason: The BCL2/Bax/Fas data support apoptosis modulation, but this is not the central BAG3 molecular role. Supporting Evidence: PMID:10597216 Bis itself exerted only weak anti-apoptotic activity, but was synergistic with Bcl-2 in preventing Bax-induced and Fas-mediated apoptosis.
GO:0005654 nucleoplasm	IDA GO_REF:0000052	KEEP AS NON CORE	Summary: Nucleoplasm localization is supported by large-scale localization and HSF1 heat-stress shuttling evidence. Reason: This is a conditional/non-core localization relative to the cytosolic CASA and chaperone-adaptor role. Supporting Evidence: PMID:26159920 BAG3 rapidly translocalized to the nucleus upon heat stress.
GO:0005829 cytosol	IDA GO_REF:0000052	ACCEPT	Summary: Cytosol localization is consistent with the main BAG3 function. Reason: BAG3 forms HSP70/sHSP/CASA complexes in the cytosol and traffics clients toward aggresomes. Supporting Evidence: file:human/BAG3/BAG3-deep-research-falcon.md See deep research file for comprehensive analysis
GO:0000774 adenyl-nucleotide exchange factor activity	IDA PMID:30559338 Myopathy associated BAG3 mutations lead to protein aggregati...	ACCEPT	Summary: BAG3 enables HSP70-family nucleotide exchange through the BAG domain. Reason: The Nat Commun disease-mechanism study and biochemical literature support the HSP70 network/NEF role. Supporting Evidence: PMID:24318877 Proteins with Bcl2-associated anthanogene (BAG) domains act as nucleotide exchange factors (NEFs) for the molecular chaperone heat shock protein 70 (Hsp70).
GO:0006457 protein folding	IDA PMID:30559338 Myopathy associated BAG3 mutations lead to protein aggregati...	ACCEPT	Summary: BAG3 participates in protein folding proteostasis through its HSP70 NEF and chaperone-scaffold functions. Reason: Although broad, protein folding reflects BAG3 core activity in HSP70/sHSP chaperone cycles; more specific molecular annotations capture the mechanism. Supporting Evidence: PMID:27884606 We report that the Hsp70 co-chaperone, BAG3, is a modular, scaffolding factor to bring together sHsps and Hsp70s.
GO:0030674 protein-macromolecule adaptor activity	IDA PMID:27884606 BAG3 Is a Modular, Scaffolding Protein that physically Links...	ACCEPT	Summary: BAG3 acts as a modular adaptor/scaffold that links HSP70 to small heat shock proteins. Reason: This is one of the best-supported molecular descriptions of BAG3 function. Supporting Evidence: PMID:27884606 We report that the Hsp70 co-chaperone, BAG3, is a modular, scaffolding factor to bring together sHsps and Hsp70s.
GO:0051087 protein-folding chaperone binding	IDA PMID:27884606 BAG3 Is a Modular, Scaffolding Protein that physically Links...	ACCEPT	Summary: BAG3 binds protein-folding chaperones, especially HSP70/HSC70 and small HSPs. Reason: The modular scaffolding study directly supports BAG3 binding to both chaperone families. Supporting Evidence: PMID:27884606 We report that the Hsp70 co-chaperone, BAG3, is a modular, scaffolding factor to bring together sHsps and Hsp70s.
GO:0051087 protein-folding chaperone binding	IDA PMID:30559338 Myopathy associated BAG3 mutations lead to protein aggregati...	ACCEPT	Summary: BAG3 chaperone binding is supported in the disease-mechanism/HSP70 network study. Reason: BAG3 interactions with HSC70/HSP70 and HSPB8 are central to its proteostasis function. Supporting Evidence: PMID:27884606 We report that the Hsp70 co-chaperone, BAG3, is a modular, scaffolding factor to bring together sHsps and Hsp70s.
GO:0140597 protein carrier activity	TAS PMID:21681022 BAG3 and friends: co-chaperones in selective autophagy durin...	MODIFY	Summary: Protein carrier activity captures part of BAG3 cargo-routing biology but is less precise than adaptor and dynein-binding functions. Reason: BAG3 does not act as a transporter in the usual sense; evidence supports coupling HSP70 clients to dynein and autophagy machinery. Proposed replacements: protein-macromolecule adaptor activity dynein intermediate chain binding Supporting Evidence: PMID:21252941 BAG3, which interacts with the microtubule-motor dynein and selectively directs Hsp70 substrates to the motor and thereby to the aggresome.
GO:0098840 protein transport along microtubule	TAS PMID:21681022 BAG3 and friends: co-chaperones in selective autophagy durin...	ACCEPT	Summary: BAG3 promotes transport of misfolded HSP70 substrates along microtubules toward aggresomes. Reason: The aggresome-targeting study directly shows BAG3-dependent coupling of clients to dynein and microtubule transport. Supporting Evidence: PMID:21252941 BAG3, which interacts with the microtubule-motor dynein and selectively directs Hsp70 substrates to the motor and thereby to the aggresome.
GO:1905337 positive regulation of aggrephagy	IMP PMID:18006506 HspB8 chaperone activity toward poly(Q)-containing proteins ...	ACCEPT	Summary: BAG3 positively regulates aggrephagy/macroautophagic disposal of aggregation-prone clients. Reason: Bag3 overexpression accelerates Htt43Q degradation and Bag3 knockdown blocks HSPB8-induced degradation. Supporting Evidence: PMID:18006506 Bag3 overexpression resulted in the accelerated degradation of Htt43Q, whereas Bag3 knockdown prevented HspB8-induced Htt43Q degradation.
GO:0005515 protein binding	IPI PMID:23434281 Cellular mechanotransduction relies on tension-induced and c...	MODIFY	Summary: BAG3-SYNPO2 binding is real but protein binding is too generic. Reason: The WW-domain interaction supports BAG3 adaptor activity during CASA/mechanotransduction rather than a standalone generic protein-binding annotation. Proposed replacements: protein-macromolecule adaptor activity Supporting Evidence: PMID:23434281 The CASA complex, comprised of the molecular chaperones Hsc70 and HspB8 and the cochaperone BAG3, senses the mechanical unfolding of the actin-crosslinking protein filamin.
GO:0010664 negative regulation of striated muscle cell apoptotic process	IMP PMID:19085932 Mutation in BAG3 causes severe dominant childhood muscular d...	KEEP AS NON CORE	Summary: BAG3-related muscle disease supports a role in muscle survival/homeostasis, but this apoptosis-specific term is secondary. Reason: The Pro209Leu muscle-disease paper reports apoptotic nuclei in BAG3opathy and links the finding to BAG3 anti-apoptotic activity, while the primary muscle mechanism remains defective CASA/Z-disc proteostasis. Supporting Evidence: PMID:19085932 The enhanced nuclear apoptosis in Bag3opathy is consistent with known antiapoptotic effect of Bag3 PMID:10597216 Bis itself exerted only weak anti-apoptotic activity, but was synergistic with Bcl-2 in preventing Bax-induced and Fas-mediated apoptosis. PMID:20060297 Stv and its mammalian ortholog BAG-3 coordinate the activity of Hsc70 and the small heat shock protein HspB8 during disposal that is initiated by the chaperone-associated ubiquitin ligase CHIP and the autophagic ubiquitin adaptor p62.
GO:0016235 aggresome	TAS PMID:21681022 BAG3 and friends: co-chaperones in selective autophagy durin...	ACCEPT	Summary: BAG3 localizes to and promotes aggresome-associated quality-control structures during stress. Reason: BAG3-positive juxtanuclear structures resemble aggresomes and BAG3 directs HSP70 substrates to the aggresome. Supporting Evidence: PMID:21252941 BAG3, which interacts with the microtubule-motor dynein and selectively directs Hsp70 substrates to the motor and thereby to the aggresome.
GO:0034620 cellular response to unfolded protein	IMP PMID:18006506 HspB8 chaperone activity toward poly(Q)-containing proteins ...	KEEP AS NON CORE	Summary: BAG3 participates in cellular responses to unfolded or aggregation-prone proteins. Reason: This broad stress-response term is supported, but the mechanistic core is chaperone-assisted selective autophagy and HSP70/sHSP scaffolding. Supporting Evidence: PMID:18006506 Bag3 overexpression resulted in the accelerated degradation of Htt43Q, whereas Bag3 knockdown prevented HspB8-induced Htt43Q degradation.
GO:0045505 dynein intermediate chain binding	NAS PMID:21252941 BAG3 mediates chaperone-based aggresome-targeting and select...	ACCEPT	Summary: BAG3 interacts with dynein intermediate chain to load HSP70 substrates onto the dynein motor. Reason: The primary aggresome-targeting study directly supports dynein interaction and cargo loading. Supporting Evidence: PMID:21252941 BAG3, which interacts with the microtubule-motor dynein and selectively directs Hsp70 substrates to the motor and thereby to the aggresome.
GO:0046716 muscle cell cellular homeostasis	IMP PMID:19085932 Mutation in BAG3 causes severe dominant childhood muscular d...	ACCEPT	Summary: BAG3 supports muscle cell homeostasis through CASA-mediated Z-disc maintenance. Reason: Muscle maintenance is a well-supported tissue-level outcome of BAG3/CASA function. Supporting Evidence: PMID:20060297 Stv and its mammalian ortholog BAG-3 coordinate the activity of Hsc70 and the small heat shock protein HspB8 during disposal that is initiated by the chaperone-associated ubiquitin ligase CHIP and the autophagic ubiquitin adaptor p62.
GO:0050821 protein stabilization	IDA PMID:18006506 HspB8 chaperone activity toward poly(Q)-containing proteins ...	MARK AS OVER ANNOTATED	Summary: Protein stabilization is related to BAG3 proteostasis but is less precise than documented chaperone-adaptor and aggrephagy functions. Reason: BAG3 can stabilize chaperone clients or complexes in some contexts, but often promotes disposal of damaged proteins; the annotation is too broad to treat as a core BAG3 function. Supporting Evidence: PMID:18006506 Bag3 overexpression resulted in the accelerated degradation of Htt43Q, whereas Bag3 knockdown prevented HspB8-induced Htt43Q degradation.
GO:0051087 protein-folding chaperone binding	IPI PMID:18006506 HspB8 chaperone activity toward poly(Q)-containing proteins ...	ACCEPT	Summary: BAG3 binds the protein-folding chaperone HSPB8 in a functional complex. Reason: The HSPB8/BAG3 interaction is central to BAG3-dependent macroautophagic disposal of aggregation-prone proteins. Supporting Evidence: PMID:18006506 Bag3 overexpression resulted in the accelerated degradation of Htt43Q, whereas Bag3 knockdown prevented HspB8-induced Htt43Q degradation.
GO:0070842 aggresome assembly	TAS PMID:21681022 BAG3 and friends: co-chaperones in selective autophagy durin...	ACCEPT	Summary: BAG3 promotes aggresome assembly as part of its selective-autophagy cargo-routing function. Reason: Knockdown and overexpression experiments support BAG3-dependent aggresome formation. Supporting Evidence: PMID:21252941 Formation of ubiquitin-positive aggresomes was decreased in BAG3 knockdown cells
GO:0101031 protein folding chaperone complex	IDA PMID:18006506 HspB8 chaperone activity toward poly(Q)-containing proteins ...	ACCEPT	Summary: BAG3 is part of a protein-folding chaperone complex with HSP70/HSC70, HSPB8, and STUB1/CHIP. Reason: CASA complex membership is directly supported in the muscle-maintenance study. Supporting Evidence: PMID:20060297 Stv and its mammalian ortholog BAG-3 coordinate the activity of Hsc70 and the small heat shock protein HspB8 during disposal that is initiated by the chaperone-associated ubiquitin ligase CHIP and the autophagic ubiquitin adaptor p62.
GO:0045296 cadherin binding	HDA PMID:25468996 E-cadherin interactome complexity and robustness resolved by...	MARK AS OVER ANNOTATED	Summary: Cadherin binding comes from a high-throughput interactome and is not supported as BAG3 core biology. Reason: The reviewed BAG3 literature supports chaperone/adaptor/CASA functions; this HDA interaction should not drive functional interpretation. Supporting Evidence: file:human/BAG3/BAG3-deep-research-falcon.md See deep research file for comprehensive analysis
GO:0042307 positive regulation of protein import into nucleus	IMP PMID:26159920 BAG3 affects the nucleocytoplasmic shuttling of HSF1 upon he...	KEEP AS NON CORE	Summary: BAG3 affects HSF1 nuclear import/accumulation during heat stress. Reason: The HSF1 shuttling phenotype is experimentally supported but is a stress-response regulatory role outside the main proteostasis/CASA core. Supporting Evidence: PMID:26159920 BAG3 rapidly translocalized to the nucleus upon heat stress.
GO:0005515 protein binding	IPI PMID:28144995 Axonal Neuropathies due to Mutations in Small Heat Shock Pro...	MODIFY	Summary: The HSPB8 interaction is real but protein binding is too generic. Reason: A more informative annotation is protein-folding chaperone binding because the evidence concerns BAG3 interaction with small heat shock proteins. Proposed replacements: protein-folding chaperone binding Supporting Evidence: PMID:27884606 We report that the Hsp70 co-chaperone, BAG3, is a modular, scaffolding factor to bring together sHsps and Hsp70s.
GO:0000774 adenyl-nucleotide exchange factor activity	IDA PMID:24318877 Binding of human nucleotide exchange factors to heat shock p...	ACCEPT	Summary: BAG3 has HSP70 nucleotide-exchange factor activity. Reason: Direct biochemical assays show BAG3 binds HSP70 strongly and functions as a BAG-family NEF. Supporting Evidence: PMID:24318877 Proteins with Bcl2-associated anthanogene (BAG) domains act as nucleotide exchange factors (NEFs) for the molecular chaperone heat shock protein 70 (Hsp70).
GO:0005515 protein binding	IPI PMID:24318877 Binding of human nucleotide exchange factors to heat shock p...	MODIFY	Summary: The BAG3-HSP70 interaction is real but generic protein binding is less informative than the NEF activity it supports. Reason: The PMID supports BAG3 interaction with HSP70 as part of nucleotide exchange/client release assays. Proposed replacements: adenyl-nucleotide exchange factor activity protein-folding chaperone binding Supporting Evidence: PMID:24318877 Proteins with Bcl2-associated anthanogene (BAG) domains act as nucleotide exchange factors (NEFs) for the molecular chaperone heat shock protein 70 (Hsp70).
GO:0005515 protein binding	IPI PMID:26159920 BAG3 affects the nucleocytoplasmic shuttling of HSF1 upon he...	MARK AS OVER ANNOTATED	Summary: The BAG3-HSF1 interaction is real but generic protein binding is uninformative. Reason: The useful biological annotation from this paper is HSF1 nucleocytoplasmic shuttling during heat stress rather than generic protein binding. Supporting Evidence: PMID:26159920 BAG3 rapidly translocalized to the nucleus upon heat stress.
GO:0005634 nucleus	IDA PMID:26159920 BAG3 affects the nucleocytoplasmic shuttling of HSF1 upon he...	KEEP AS NON CORE	Summary: BAG3 translocates to or colocalizes in the nucleus during heat stress. Reason: Nuclear BAG3 is experimentally observed but condition-dependent. Supporting Evidence: PMID:26159920 BAG3 rapidly translocalized to the nucleus upon heat stress.
GO:0005737 cytoplasm	IDA PMID:26159920 BAG3 affects the nucleocytoplasmic shuttling of HSF1 upon he...	ACCEPT	Summary: BAG3 is observed in the cytoplasm and has its major co-chaperone functions there. Reason: Cytoplasmic BAG3 is directly observed and consistent with the CASA/chaperone literature. Supporting Evidence: PMID:26159920 BAG3 rapidly translocalized to the nucleus upon heat stress.
GO:0034605 cellular response to heat	IDA PMID:26159920 BAG3 affects the nucleocytoplasmic shuttling of HSF1 upon he...	KEEP AS NON CORE	Summary: BAG3 is part of the heat-stress response through HSF1 shuttling. Reason: This is supported but context-specific; BAG3 core molecular role remains HSP70/sHSP adaptor and CASA proteostasis. Supporting Evidence: PMID:26159920 BAG3 rapidly translocalized to the nucleus upon heat stress.
GO:0046827 positive regulation of protein export from nucleus	IMP PMID:26159920 BAG3 affects the nucleocytoplasmic shuttling of HSF1 upon he...	KEEP AS NON CORE	Summary: BAG3 promotes HSF1 export from the nucleus during heat-stress recovery. Reason: The process is experimentally supported but is not the principal BAG3 function. Supporting Evidence: PMID:26159920 Over-expression of BAG3 down-regulates the level of nuclear HSF1 by exporting it to the cytoplasm during the recovery period.
GO:0000774 adenyl-nucleotide exchange factor activity	IDA PMID:20060297 Chaperone-assisted selective autophagy is essential for musc...	ACCEPT	Summary: BAG3 nucleotide-exchange activity is also consistent with CASA complex work. Reason: The CASA complex requires BAG3 as an HSP70/HSC70 co-chaperone; biochemical NEF evidence from BAG-domain studies further supports the term. Supporting Evidence: PMID:20060297 Stv and its mammalian ortholog BAG-3 coordinate the activity of Hsc70 and the small heat shock protein HspB8 during disposal that is initiated by the chaperone-associated ubiquitin ligase CHIP and the autophagic ubiquitin adaptor p62. PMID:24318877 Proteins with Bcl2-associated anthanogene (BAG) domains act as nucleotide exchange factors (NEFs) for the molecular chaperone heat shock protein 70 (Hsp70).
GO:0005829 cytosol	TAS Reactome:R-HSA-5252079	ACCEPT	Summary: Reactome places BAG-family NEF activity in the cytosolic HSP70 nucleotide-exchange pathway. Reason: The Reactome event supports cytosolic BAG-family control of HSP70 ADP/ATP exchange. Supporting Evidence: Reactome:R-HSA-5252079 Eukaryote NEFs include heat-shock protein 105kDa (HSPH1 aka HSP110) (Schuermann et al. 2008) and the BAG family molecular chaperone regulator (BAG) family (BAG1-5).
GO:0008625 extrinsic apoptotic signaling pathway via death domain receptors	IDA PMID:10597216 Bis, a Bcl-2-binding protein that synergizes with Bcl-2 in p...	KEEP AS NON CORE	Summary: BAG3 can modulate Fas-mediated apoptotic signaling through BCL2 interaction, but this is non-core. Reason: The apoptosis data are real but secondary to BAG3 proteostasis and co-chaperone functions. Supporting Evidence: PMID:10597216 Bis itself exerted only weak anti-apoptotic activity, but was synergistic with Bcl-2 in preventing Bax-induced and Fas-mediated apoptosis.
GO:0005515 protein binding	IPI PMID:22366786 Mutations affecting the cytoplasmic functions of the co-chap...	MODIFY	Summary: DNAJB6 interaction is plausible chaperone-network biology, but protein binding is too generic. Reason: BAG3 participates in chaperone networks; protein-folding chaperone binding is more informative than generic protein binding. Proposed replacements: protein-folding chaperone binding Supporting Evidence: file:human/BAG3/BAG3-deep-research-falcon.md See deep research file for comprehensive analysis
GO:0006457 protein folding	NAS PMID:9873016 An evolutionarily conserved family of Hsp70/Hsc70 molecular ...	ACCEPT	Summary: BAG3 participates in protein folding proteostasis through its HSP70 NEF and chaperone-scaffold functions. Reason: Although broad, protein folding reflects BAG3 core activity in HSP70/sHSP chaperone cycles; more specific molecular annotations capture the mechanism. Supporting Evidence: PMID:24318877 Proteins with Bcl2-associated anthanogene (BAG) domains act as nucleotide exchange factors (NEFs) for the molecular chaperone heat shock protein 70 (Hsp70).
GO:0043066 negative regulation of apoptotic process	NAS PMID:10597216 Bis, a Bcl-2-binding protein that synergizes with Bcl-2 in p...	KEEP AS NON CORE	Summary: BAG3 has anti-apoptotic activity through BCL2 cooperation. Reason: This annotation is supported, but apoptosis regulation is not the main conserved molecular function. Supporting Evidence: PMID:10597216 Bis itself exerted only weak anti-apoptotic activity, but was synergistic with Bcl-2 in preventing Bax-induced and Fas-mediated apoptosis.
GO:0005829 cytosol	IDA PMID:10597216 Bis, a Bcl-2-binding protein that synergizes with Bcl-2 in p...	ACCEPT	Summary: BAG3 is cytosolic in the BCL2-interaction/anti-apoptotic context and broader proteostasis literature. Reason: Cytosol is a supported localization for BAG3. Supporting Evidence: file:human/BAG3/BAG3-deep-research-falcon.md See deep research file for comprehensive analysis

Gene Description

Existing Annotations Review

Core Functions

HSP70 nucleotide-exchange co-chaperone activity: BAG3 uses its BAG domain to bind HSP70/HSC70 nucleotide-binding domains and promote ADP release/client release in protein-folding chaperone cycles.

Modular chaperone adaptor/scaffold activity: BAG3 links HSP70/HSC70 with small heat shock proteins including HSPB8 and HSPB1/HSP27, coordinating client handling by ATP-dependent and ATP-independent chaperones.

Chaperone-assisted selective autophagy and aggrephagy: BAG3-HSP70-HSPB8 complexes route damaged or aggregation-prone clients to aggresomes and autophagic degradation with dynein, STUB1/CHIP, p62/SQSTM1, and LC3-linked machinery.

Striated muscle Z-disc proteostasis and mechanotransduction: BAG3-containing CASA machinery senses mechanically damaged filamin and other Z-disc components, supports autophagosome formation, and maintains muscle cell homeostasis under mechanical stress.

References

Suggested Questions for Experts

Suggested Experiments

Deep Research

Falcon

📚 Additional Documentation

Notes

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