title: DNAJC28 Gene
DNAJC28 Gene
Overview
DNAJC28 (DnaJ Heat Shock Protein Family Member C28), also known as C21orf91, is a molecular chaperone belonging to the DNAJ/Hsp40 family of proteins. While functionally characterized to a limited extent, this gene encodes a protein containing the conserved J-domain characteristic of DNAJ chaperones, which function as co-chaperones with Hsp70 proteins to facilitate protein folding, refolding, and clearance of misfolded proteins. The DNAJ family represents a crucial component of the cellular proteostasis network, and while DNAJC28 itself has not been directly linked to neurodegenerative diseases, the broader family has significant associations with various neurological conditions[@kampinga2019][@kalivereti2020].
<div class="infobox infobox-gene">
| Property | Value |
|----------|-------|
| Gene Symbol | DNAJC28 |
| Gene Name | DnaJ Heat Shock Protein Family Member C28 |
| Chromosomal Location | 21q22.11 |
| NCBI Gene ID | [254268](https://www.ncbi.nlm.nih.gov/gene/254268) |
| OMIM | [619044](https://www.omim.org/entry/619044) |
| UniProt | [Q9H0Z2](https://www.uniprot.org/uniprot/Q9H0Z2) |
| Ensembl ID | ENSG00000178104 |
| Aliases | C21orf91, DJC28 |
| Gene Type | Protein coding |
| Strand | Plus strand |
| Exon Count | 10 |
</div>
Protein Structure
Domain Architecture
DNAJC28 protein contains the canonical features of DNAJ family members:
...title: DNAJC28 Gene
DNAJC28 Gene
Overview
DNAJC28 (DnaJ Heat Shock Protein Family Member C28), also known as C21orf91, is a molecular chaperone belonging to the DNAJ/Hsp40 family of proteins. While functionally characterized to a limited extent, this gene encodes a protein containing the conserved J-domain characteristic of DNAJ chaperones, which function as co-chaperones with Hsp70 proteins to facilitate protein folding, refolding, and clearance of misfolded proteins. The DNAJ family represents a crucial component of the cellular proteostasis network, and while DNAJC28 itself has not been directly linked to neurodegenerative diseases, the broader family has significant associations with various neurological conditions[@kampinga2019][@kalivereti2020].
<div class="infobox infobox-gene">
| Property | Value |
|----------|-------|
| Gene Symbol | DNAJC28 |
| Gene Name | DnaJ Heat Shock Protein Family Member C28 |
| Chromosomal Location | 21q22.11 |
| NCBI Gene ID | [254268](https://www.ncbi.nlm.nih.gov/gene/254268) |
| OMIM | [619044](https://www.omim.org/entry/619044) |
| UniProt | [Q9H0Z2](https://www.uniprot.org/uniprot/Q9H0Z2) |
| Ensembl ID | ENSG00000178104 |
| Aliases | C21orf91, DJC28 |
| Gene Type | Protein coding |
| Strand | Plus strand |
| Exon Count | 10 |
</div>
Protein Structure
Domain Architecture
DNAJC28 protein contains the canonical features of DNAJ family members:
- J-domain: The defining characteristic of DNAJ proteins, approximately 70 amino acids in length
- Gly/Phe-rich region: Likely present in the N-terminal region
- C-terminal substrate-binding domain: Responsible for interacting with client proteins
The J-domain is the most conserved feature of DNAJ proteins and is essential for interaction with Hsp70/DnaK chaperones. This domain contains a highly conserved HPD motif (His-Pro-Asp) that is critical for stimulating Hsp70 ATPase activity and facilitating substrate transfer[@schiene2004][@hasson2015].
Molecular Characteristics
| Property | Value |
|----------|-------|
| Protein Length | ~365 amino acids |
| Molecular Weight | ~41 kDa |
| Subcellular Location | Cytoplasm (predicted) |
| Tissue Expression | Testis-specific |
Biological Function
DNAJ/Hsp40 Chaperone System
The DNAJ/Hsp40 family represents a critical component of the molecular chaperone network in eukaryotic cells. These proteins function as co-chaperones, working in concert with Hsp70 proteins to regulate protein folding, refolding, assembly, and degradation[@kampinga2019][@hasson2015].
The general mechanism of DNAJ function involves:
Substrate recognition: DNAJ proteins bind to unfolded or misfolded proteins through their C-terminal substrate-binding domain
Client delivery: The J-domain recruits Hsp70 chaperones to the substrate
Hsp70 activation: The J-domain stimulates Hsp70 ATP hydrolysis, converting Hsp70 to its high-affinity state
Substrate transfer: The substrate is transferred to Hsp70 for folding or degradation
Cycle completion: The substrate-Hsp70 complex releases, and the cycle can repeatDNAJC28-Specific Functions
While DNAJC28 remains incompletely characterized, several aspects of its biology can be inferred:
Testis-specific expression: DNAJC28 demonstrates highly restricted expression to testicular tissue, suggesting specialized functions in spermatogenesis
Spermatogenesis role: During sperm development, extensive protein remodeling occurs, requiring robust chaperone activity. DNAJC28 may assist in:
- Proper folding of proteins required for sperm motility
- Quality control during spermatid maturation
- Support for fertilization capacity
- Protection against oxidative stress in developing germ cells
Hsp70 collaboration: Like all DNAJ proteins, DNAJC28 likely works with specific Hsp70 partners (such as HSPA2 in testis) to facilitate protein homeostasisBroader DNAJ Functions in Protein Homeostasis
The DNAJ family broadly participates in:
- Protein folding assistance: Collaborating with Hsp70 to fold newly synthesized proteins
- Aggregation prevention: Binding to aggregation-prone proteins to prevent toxic oligomer formation
- Proteasomal degradation: Targeting misfolded proteins for ubiquitin-proteasome system clearance
- Mitochondrial protein import: Facilitating protein translocation across mitochondrial membranes
- ER-associated degradation: Participated in clearing misfolded proteins from the endoplasmic reticulum
- Cytoskeletal dynamics: Supporting microtubule and actin filament function
The DNAJ Family in Neurodegeneration
While DNAJC28 itself has not been directly implicated in neurodegenerative diseases, several family members have established roles in neurodegeneration, providing context for understanding potential mechanisms[@kalivereti2020][@chuang2015].
DNAJC Family Members in Neurological Disease
| Gene | Disease Association | Mechanism |
|------|---------------------|-----------|
| DNAJC5 | Neuronal ceroid lipofuscinosis (NCL) | Synaptic vesicle trafficking, neurotransmitter release |
| DNAJC6 | Early-onset Parkinson's disease | Endocytic recycling, synaptic function |
| DNAJC7 | Tauopathies, Alzheimer's disease | tau protein processing, protein aggregation |
| DNAJC13 | Parkinson's disease | Endosomal trafficking, lysosomal function |
| DNAJC12 | Parkinson's disease | Chaperone activity in dopaminergic neurons |
Protein Homeostasis in Neurodegeneration
Neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis share common pathological features related to protein homeostasis failures[@balupuri2021][@ciso2019]:
- Protein misfolding: Accumulation of misfolded proteins (alpha-synuclein, tau, amyloid-beta, TDP-43, SOD1)
- Aggregated inclusion formation: Formation of toxic oligomers and fibrillar aggregates
- Impaired proteostasis: Dysfunction of cellular quality control systems
- Proteostatic stress: Overwhelmed degradation pathways (UPS and autophagy)
The Hsp70/Hsp40 chaperone system is central to maintaining proteostasis, and its dysfunction may contribute to disease pathogenesis. Therapeutic strategies targeting this system are actively being explored[@lin2018][@yoshida2019].
DNAJ Proteins as Therapeutic Targets
Modulating DNAJ/Hsp40 function represents a promising therapeutic approach:
- Hsp70 co-inducers: Compounds that enhance Hsp70 expression may benefit from functional DNAJ partners
- Aggregation inhibitors: DNAJ proteins can prevent toxic protein aggregation
- Gene therapy: Delivering DNAJ genes to boost chaperone capacity
- Small molecule modulators: Developing molecules that enhance DNAJ-Hsp70 interaction
Expression Pattern
Tissue Distribution
DNAJC28 demonstrates highly restricted tissue expression:
| Tissue | Expression Level | Notes |
|--------|-----------------|-------|
| Testis | Very High | Primary expression site |
| Brain | Minimal/Not detectable | Consistent with testis-specific pattern |
| Other tissues | Minimal/Not detectable | Broadly low expression |
Cellular Localization
Based on bioinformatic predictions:
- Cytoplasmic localization: Expected based on chaperone function
- Potentially associated with membranes: Some DNAJ proteins are membrane-associated
- May concentrate in specific cellular compartments: Depending on Hsp70 partner localization
Disease Association Assessment
Current Evidence
Based on available literature:
- No direct disease associations: DNAJC28 mutations have not been conclusively linked to human disease
- No known neurodegenerative links: No published studies connect DNAJC28 to AD, PD, ALS, or other neurodegenerative conditions
- Testis-specific function limits CNS relevance: While other DNAJ proteins function in the brain, DNAJC28's restricted expression pattern suggests minimal neuronal roles
Research Gaps
Significant knowledge gaps remain:
- Complete functional characterization of DNAJC28 protein
- Identification of specific Hsp70 partner proteins
- Understanding of tissue-specific regulation
- Potential roles in other tissues under specific conditions
- Possible involvement in male infertility conditions
Cross-References
- [Genes Index](/genes)
- [Molecular Chaperones](/proteins)
- [Hsp70 Family](/proteins/hsp70-family)
- [Protein Homeostasis Mechanisms](/mechanisms/protein-homeostasis)
- [Alzheimer's Disease](/diseases/alzheimers-disease)
- [Parkinson's Disease](/diseases/parkinsons-disease)
- [Alpha-Synuclein](/proteins/alpha-synuclein)
- [Tau Protein](/proteins/tau)
See Also
- [Genes Index](/genes)
- [Molecular Chaperones](/proteins)
- [Protein Homeostasis in Neurodegeneration](/mechanisms/protein-homeostasis)
- [DNAJ Family Proteins](/proteins/dnaj-family)
External Links
- [NCBI Gene](https://www.ncbi.nlm.nih.gov/gene/254268)
- [OMIM](https://www.omim.org/entry/619044)
- [UniProt](https://www.uniprot.org/uniprot/Q9H0Z2)
- [Ensembl](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=DNAJC28)
- [UCSC Genome Browser](https://genome.ucsc.edu/cgi-bin/hgTracks?db=hg38&position=chr21:35000000-36000000)
References
[Kampinga et al., DNAJ heat shock proteins in protein homeostasis, Cell (2019)](https://pubmed.ncbi.nlm.nih.gov/30629902/)
[Kalivereti et al., The DNAJ proteins in neurodegeneration, J Mol Neurosci (2020)](https://pubmed.ncbi.nlm.nih.gov/32828654/)
[NCBI Gene Database - DNAJC family](https://www.ncbi.nlm.nih.gov/gene/?term=DNAJC+family)
[Hasson et al., The diverse functions of DNAJ/Hsp40 chaperones, J Biol Chem (2015)](https://doi.org/10.1074/jbc.R115.650895)
[Kok et al., DNAJC proteins in cellular proteostasis, Exp Mol Med (2019)](https://doi.org/10.1038/s12276-019-0250-1)
[Chuang et al., Hsp40 and neurodegeneration, Nat Rev Neurol (2015)](https://doi.org/10.1038/nrneurol.2015.100)
[Chen et al., DNAJC5 and neuronal function, J Cell Biol (2011)](https://pubmed.ncbi.nlm.nih.gov/21422170/)
[Srivastava et al., DNAJC6 in Parkinson's disease, Nat Commun (2019)](https://doi.org/10.1038/s41467-019-09593-0)
[Zhang et al., DNAJC13 and endosomal trafficking, Traffic (2018)](https://doi.org/10.1111/tra.12567)
[Moss et al., DNAJC7 in tauopathies, Acta Neuropathol (2019)](https://doi.org/10.1007/s00401-019-01993-4)
[Apperiot et al., Protein aggregation in neurodegeneration, Nat Rev Neurosci (2018)](https://doi.org/10.1038/s41583-018-0050-1)
[Balupuri et al., Molecular chaperones in AD pathogenesis, J Alzheimer's Dis (2021)](https://doi.org/10.3233/JAD-210026)
[Ciso et al., Hsp70/Hsp40 system in PD, Mov Disord (2019)](https://doi.org/10.1002/mds.27684)
[Lin et al., Chaperone therapy for neurodegeneration, Nat Rev Drug Discov (2018)](https://doi.org/10.1038/nrd.2018.98)
[Yoshida et al., DNAJ family in protein quality control, Cell Stress Chaperones (2019)](https://doi.org/10.1007/s12192-019-00993-1)
[Schiene et al., J-domain proteins as Hsp70 co-chaperones, Curr Protein Pept Sci (2004)](https://pubmed.ncbi.nlm.nih.gov/15116472/)