BAG family molecular chaperone regulator 3 is a

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...

that in humans is encoded by the ''BAG3''

gene In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...

. BAG3 is involved in

chaperone-assisted selective autophagy Chaperone-assisted selective autophagy is a cellular process for the selective, ubiquitin-dependent degradation of chaperone-bound proteins in lysosomes. Autophagy (Greek: ‘self-eating’) was initially identified as a catabolic process for the ...

Function

BAG proteins compete with

Hip-1 Huntingtin-interacting protein 1 also known as HIP-1 is a protein that in humans is encoded by the HIP1 gene. Hip-1 is a protein that interacts with the huntingtin protein. It is known to contain a domain homologous to the death effector domains ( ...

for binding to the

Hsc70 Heat shock 70 kDa protein 8 also known as heat shock cognate 71 kDa protein or Hsc70 or Hsp73 is a heat shock protein that in humans is encoded by the ''HSPA8'' gene on chromosome 11. As a member of the heat shock protein 70 family and a chaperon ...

Hsp70 The 70 kilodalton heat shock proteins (Hsp70s or DnaK) are a family of conserved ubiquitously expressed heat shock proteins. Proteins with similar structure exist in virtually all living organisms. Intracellularly localized Hsp70s are an import ...

ATPase domain and promote substrate release. All the BAG proteins have an approximately 45-amino acid

BAG domain In molecular biology, BAG domains are protein domains found in proteins which are modulators of chaperone activity, they bind to HSP70/HSC70 proteins and promote substrate release. The proteins have anti-apoptotic activity and increase the anti- ...

near the

C terminus The C-terminus (also known as the carboxyl-terminus, carboxy-terminus, C-terminal tail, C-terminal end, or COOH-terminus) is the end of an amino acid chain (protein or polypeptide), terminated by a free carboxyl group (-COOH). When the protein is ...

but differ markedly in their N-terminal regions. The protein encoded by this gene contains a

WW domain The WW domain, (also known as the rsp5-domain or WWP repeating motif) is a modular protein domain that mediates specific interactions with protein ligands. This domain is found in a number of unrelated signaling and structural proteins and may be ...

in the N-terminal region and a BAG domain in the C-terminal region. The BAG domains of

BAG1 BAG family molecular chaperone regulator 1 is a protein that in humans is encoded by the ''BAG1'' gene. Function The oncogene BCL2 is a membrane protein that blocks a step in a pathway leading to apoptosis or programmed cell death. The protei ...

BAG2 BAG family molecular chaperone regulator 2 is a protein that in humans is encoded by the ''BAG2'' gene. BAG proteins compete with Hip for binding to the Hsc70/Hsp70 ATPase domain and promote substrate release. All the BAG proteins have an approxi ...

, and BAG3 interact specifically with the Hsc70 ATPase domain ''in vitro'' and in mammalian cells. All 3 proteins bind with high affinity to the ATPase domain of Hsc70 and inhibit its chaperone activity in a Hip-repressible manner.

Clinical significance

BAG gene has been implicated in age related neurodegenerative diseases such as Alzheimer's. It has been demonstrated that BAG1 and BAG3 regulate the proteasomal and lysosomal protein elimination pathways, respectively. It has also been shown to be a cause of familial dilated cardiomyopathy. That BAG3 mutations are responsible for familial dilated cardiomyopathy is confirmed by another study describing 6 new molecular variants (2 missense and 4 premature Stops ). Moreover, the same publication reported that BAG3 polymorphisms are also associated with sporadic forms of the disease together with HSPB7 locus. In muscle cells, BAG3 cooperates with the molecular chaperones Hsc70 and HspB8 to induce the degradation of mechanically damaged cytoskeleton components in lysosomes. This process is called

and is essential for maintaining muscle activity in flies, mice and men. BAG3 is able to stimulate the expression of

cytoskeleton The cytoskeleton is a complex, dynamic network of interlinking protein filaments present in the cytoplasm of all cells, including those of bacteria and archaea. In eukaryotes, it extends from the cell nucleus to the cell membrane and is com ...

proteins in response to mechanical tension by activating the

transcription Transcription refers to the process of converting sounds (voice, music etc.) into letters or musical notes, or producing a copy of something in another medium, including: Genetics * Transcription (biology), the copying of DNA into RNA, the fir ...

regulators

YAP1 YAP1 (yes-associated protein 1), also known as YAP or YAP65, is a protein that acts as a transcription coregulator that promotes transcription of genes involved in cellular proliferation and suppressing apoptotic genes. YAP1 is a component in th ...

and

WWTR1 WW domain-containing transcription regulator protein 1 (WWTR1), also known as Transcriptional coactivator with PDZ-binding motif (TAZ), is a protein that in humans is encoded by the ''WWTR1'' gene. WWTR1 acts as a transcriptional coregulator a ...

. BAG3 balances protein synthesis and protein degradation under mechanical stress.

Interactions

PLCG1 has been shown to

interact Advocates for Informed Choice, dba interACT or interACT Advocates for Intersex Youth, is a 501(c)(3) nonprofit organization using innovative strategies to advocate for the legal and human rights of children with intersex traits. The organizati ...

with: *

FGFR1 Fibroblast growth factor receptor 1 (FGFR1), also known as basic fibroblast growth factor receptor 1, fms-related tyrosine kinase-2 / Pfeiffer syndrome, and CD331, is a receptor tyrosine kinase whose ligands are specific members of the fibroblast ...

, *

CD117 Proto-oncogene c-KIT is the gene encoding the receptor tyrosine kinase protein known as tyrosine-protein kinase KIT, CD117 (cluster of differentiation 117) or mast/stem cell growth factor receptor (SCFR). Multiple transcript variants encoding diff ...

, *

CD31 Platelet endothelial cell adhesion molecule (PECAM-1) also known as cluster of differentiation 31 (CD31) is a protein that in humans is encoded by the ''PECAM1'' gene found on chromosome17q23.3. PECAM-1 plays a key role in removing aged neutrop ...

, *

Cbl gene ''Cbl'' (named after Casitas B-lineage Lymphoma) is a mammalian gene encoding the protein CBL which is an E3 ubiquitin-protein ligase involved in cell signalling and protein ubiquitination. Mutations to this gene have been implicated in a numbe ...

* CISH *

Epidermal growth factor receptor The epidermal growth factor receptor (EGFR; ErbB-1; HER1 in humans) is a transmembrane protein that is a receptor for members of the epidermal growth factor family (EGF family) of extracellular protein ligands. The epidermal growth factor rece ...

, *

Eukaryotic translation elongation factor 1 alpha 1 Elongation factor 1-alpha 1 (eEF1a1) is a translation elongation protein, expressed across eukaryotes. In humans, it is encoded by the ''EEF1A1'' gene. This gene encodes an isoform of the alpha subunit of the elongation factor-1 complex, which ...

, *

FLT1 Vascular endothelial growth factor receptor 1 is a protein that in humans is encoded by the ''FLT1'' gene. Function ''FLT1'' is a member of VEGF receptor gene family. It encodes a receptor tyrosine kinase which is activated by VEGF-A, VEGF-B ...

, *

GAB1 GRB2-associated-binding protein 1 is a protein that in humans is encoded by the ''GAB1'' gene. Function The protein encoded by this gene is a member of the IRS1-like multisubstrate docking protein family. The encoded protein is an important m ...

, *

GIT1 ARF GTPase-activating protein GIT1 is an enzyme that in humans is encoded by the ''GIT1'' gene. GIT1 contains an ARFGAP domain, Anykrin repeats, and a GRK-interacting domain. The Arf-GAP domain, which enables it to act as a GTPase activating prot ...

, * Grb2, *

HER2/neu Receptor tyrosine-protein kinase erbB-2 is a protein that in humans is encoded by the ''ERBB2'' gene. ERBB is abbreviated from erythroblastic oncogene B, a gene originally isolated from the avian genome. The human protein is also frequently refer ...

, * IRS2, *

ITK Itk is a framework for building mega-widgets using the Incr Tcl incr Tcl (commonly stylised as '' ncr Tcl/nowiki>'', and often abbreviated to ''itcl'') is a set of object-oriented extensions for the Tcl programming language. It is widely us ...

, *

KHDRBS1 KH domain-containing, RNA-binding, signal transduction-associated protein 1 is a protein that in humans is encoded by the ''KHDRBS1'' gene. This gene encodes a member of the K homology domain-containing, RNA-binding, signal transduction-associate ...

, *

Linker of activated T cells The Linker for activation of T cells, also known as linker of activated T cells or LAT, is a protein involved in the T-cell antigen receptor signal transduction pathway which in humans is encoded by the ''LAT'' gene. Alternative splicing results ...

, *

Lymphocyte cytosolic protein 2 Lymphocyte cytosolic protein 2 (SH2 domain containing leukocyte protein of 76kDa), also known as LCP2 or SLP-76, is a signal-transducing adaptor protein expressed in T cells and myeloid cells and is important in the signaling of T-cell receptors ...

, *

PDGFRA PDGFRA, i.e. platelet-derived growth factor receptor A, also termed PDGFRα, i.e. platelet-derived growth factor receptor α, or CD140a i.e. Cluster of Differentiation 140a, is a receptor located on the surface of a wide range of cell types. This re ...

, *

PLD2 Phospholipase D2 is an enzyme that in humans is encoded by the ''PLD2'' gene. Function Phosphatidylcholine (PC)-specific phospholipases D (PLDs) catalyze the hydrolysis of PC to produce phosphatidic acid and choline. Activation of PC-specifi ...

, *

RHOA Transforming protein RhoA, also known as Ras homolog family member A (RhoA), is a small GTPase protein in the Rho family of GTPases that in humans is encoded by the ''RHOA'' gene. While the effects of RhoA activity are not all well known, it is ...

, *

SOS1 Son of sevenless homolog 1 is a protein that in humans is encoded by the ''SOS1'' gene. Function SOS1 is a guanine nucleotide exchange factor (GEF) which interacts with RAS proteins to phosphorylate GDP into GTP, or from an inactive state to an ...

, * TUB, *

TrkA Tropomyosin receptor kinase A (TrkA), also known as high affinity nerve growth factor receptor, neurotrophic tyrosine kinase receptor type 1, or TRK1-transforming tyrosine kinase protein is a protein that in humans is encoded by the ''NTRK1'' gen ...

, *

TrkB Tropomyosin receptor kinase B (TrkB), also known as tyrosine receptor kinase B, or BDNF/NT-3 growth factors receptor or neurotrophic tyrosine kinase, receptor, type 2 is a protein that in humans is encoded by the ''NTRK2'' gene. TrkB is a recepto ...

, *

VAV1 Proto-oncogene vav is a protein that in humans is encoded by the ''VAV1'' gene. Function The protein encoded by this proto-oncogene is a member of the Dbl family of guanine nucleotide exchange factors (GEF) for the Rho family of GTP binding ...

, and * Wiskott-Aldrich syndrome protein.

References

External links

GeneReviews/NIH/NCBI/UW entry on Myofibrillar Myopathy
* * {{DEFAULTSORT:Bag3 Ageing Aging-related genes Aging-related proteins Co-chaperones

Function

Clinical significance

Interactions

References

Further reading

External links