<div class="infobox infobox-protein">
| | |
|---|---|
| Protein Name | DNAJC14 (DnaJ Homolog, Subfamily C, Member 14) |
| Gene | [DNAJC14](/genes/dnajc14) |
| UniProt ID | [Q9Y2H1](https://www.uniprot.org/uniprot/Q9Y2H1) |
| Molecular Weight | ~55.8 kDa (513 amino acids) |
| Subcellular Localization | Cytoplasm, Endoplasmic Reticulum |
| Protein Family | DnaJ/Hsp40 Chaperone Family |
| Chromosomal Location | 12q13.12 |
| Brain Expression | Cortex, Hippocampus, Spinal cord |
</div>
DNAJC14 (also known as HDJ3, Hsp40, or DNAJ homolog subfamily C member 14) is a member of the DnaJ/Hsp40 family of molecular co-chaperones that work in concert with Hsp70 family proteins to facilitate protein folding, refolding, and degradation. DNAJC14 is characterized by its modular domain architecture, with a J domain that stimulates Hsp70 ATPase activity, a glycine/phenylalanine-rich region that provides flexibility, and a C-terminal client-binding domain that recognizes specific substrate proteins[@kampinga2010].
<div class="infobox infobox-protein">
| | |
|---|---|
| Protein Name | DNAJC14 (DnaJ Homolog, Subfamily C, Member 14) |
| Gene | [DNAJC14](/genes/dnajc14) |
| UniProt ID | [Q9Y2H1](https://www.uniprot.org/uniprot/Q9Y2H1) |
| Molecular Weight | ~55.8 kDa (513 amino acids) |
| Subcellular Localization | Cytoplasm, Endoplasmic Reticulum |
| Protein Family | DnaJ/Hsp40 Chaperone Family |
| Chromosomal Location | 12q13.12 |
| Brain Expression | Cortex, Hippocampus, Spinal cord |
</div>
DNAJC14 (also known as HDJ3, Hsp40, or DNAJ homolog subfamily C member 14) is a member of the DnaJ/Hsp40 family of molecular co-chaperones that work in concert with Hsp70 family proteins to facilitate protein folding, refolding, and degradation. DNAJC14 is characterized by its modular domain architecture, with a J domain that stimulates Hsp70 ATPase activity, a glycine/phenylalanine-rich region that provides flexibility, and a C-terminal client-binding domain that recognizes specific substrate proteins[@kampinga2010].
The Hsp70/Hsp40 chaperone system is essential for cellular protein homeostasis, particularly in the endoplasmic reticulum (ER) where DNAJC14 plays a critical role in ER-associated degradation (ERAD). This pathway recognizes misfolded proteins in the ER, retrotranslocates them to the cytoplasm, and targets them for ubiquitin-proteasomal degradation. Proper function of this system is crucial for neuronal survival, as neurons are particularly vulnerable to proteotoxic stress[@stress2019][@chaperonemediated2016].
DNAJC14 has been implicated in several neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS), Parkinson's disease, and hereditary spastic paraplegia (HSP). Mutations in DNAJC14 have been associated with familial forms of these disorders, and altered expression or function of DNAJC14 contributes to disease pathogenesis through impairment of protein quality control mechanisms[@dixon2015][@gao2019].
The human DNAJC14 gene is located on chromosome 12q13.12 and spans approximately 8.5 kb. The gene consists of 11 exons that encode a 513-amino acid protein. Multiple transcript variants have been identified, though the canonical isoform is the predominant functional form.
DNAJC14 contains three distinct functional domains:
J Domain (aa 1-70): The N-terminal J domain is the signature feature of all DnaJ family proteins. This domain stimulates the ATPase activity of Hsp70 proteins, accelerating the cycles of substrate binding and release. The J domain contains the conserved HPD motif (His-Pro-Asp) that is essential for Hsp70 interaction. DNAJC14 interacts with both cytosolic Hsp70 (HSPA1A) and ER-resident Hsp70 (BiP/HSPA5) through its J domain.
Gly/Phe-Rich Region (aa 70-150): This flexible, low-complexity region contains multiple glycine and phenylalanine residues that may serve as a flexible linker between the J domain and the client-binding domain. This region may also contain nuclear localization signals, as DNAJC14 has been detected in both the cytoplasm and nucleus.
C-terminal Client-Binding Domain (aa 150-513): The C-terminal region is responsible for recognizing and binding client proteins. This domain contains multiple tetratricopeptide repeat (TPR) motifs that mediate protein-protein interactions. The client-binding domain determines the substrate specificity of DNAJC14 and determines which Hsp70 partners it can engage.
Crystal structures of the DNAJC14 J domain have revealed the molecular basis for its interaction with Hsp70:
DNAJC14 assists Hsp70 in protein folding through multiple mechanisms:
Co-chaperone Activity: The J domain stimulates Hsp70 ATP hydrolysis, converting Hsp70 from a low-affinity state (ATP-bound) to a high-affinity state (ADP-bound) that stably binds client proteins. This cycle is essential for protein folding efficiency.
Substrate Delivery: DNAJC14 delivers client proteins to Hsp70, facilitating their transfer from the J domain to the Hsp70 substrate-binding domain.
Refolding of Damaged Proteins: Following cellular stress (heat shock, oxidative stress), DNAJC14 helps refold denatured proteins in collaboration with Hsp70.
DNAJC14 plays a central role in ERAD:
Substrate Recognition: DNAJC14 recognizes misfolded proteins in the ER lumen or membrane that are destined for degradation.
Retrotranslocation Coordination: DNAJC14 participates in the retrotranslocation of misfolded proteins across the ER membrane to the cytosol.
Cytosolic Hsp70 Recruitment: DNAJC14 recruits cytosolic Hsp70 to facilitate ubiquitylation and proteasomal degradation of retrotranslocated substrates.
Quality Control Enforcer: By targeting terminally misfolded proteins for degradation, DNAJC14 helps maintain ER homeostasis and prevents accumulation of toxic aggregates.
Beyond ERAD, DNAJC14 contributes to general cellular protein quality control:
Cytosolic Chaperone Function: DNAJC14 can function in the cytosol to assist Hsp70 in folding newly synthesized proteins.
Aggresome Targeting: DNAJC14 helps target misfolded proteins to aggresomes, a form of cytoplasmic inclusion that sequesters potentially toxic proteins.
Autophagy Regulation: DNAJC14 influences autophagy pathways that clear damaged proteins and organelles[@yang2020].
DNAJC14 exhibits region-specific expression:
At the cellular level, DNAJC14 localizes to:
Multiple studies have implicated DNAJC14 in ALS pathogenesis:
Expression Changes: DNAJC14 expression is altered in ALS motor cortex and spinal cord. Some studies show increased expression, possibly as a compensatory response to proteotoxic stress.
Genetic Association: Rare variants in DNAJC14 have been identified in some ALS patients, though these are not common ALS-causing mutations.
Protein Aggregation: DNAJC14 is found in inclusion bodies in ALS models and patient tissue, suggesting it may be sequestered into aggregates.
DNAJC4 dysfunction contributes to ALS through several mechanisms:
Impaired ERAD: Mutations in ALS-associated proteins (SOD1, TDP-43, FUS) can overwhelm the ERAD system. DNAJC14 dysfunction further impairs this pathway, leading to ER stress and activation of the unfolded protein response (UPR).
Mitochondrial Protein Quality Control: DNAJC14 participates in mitochondrial protein import and quality control. Dysfunction contributes to mitochondrial dysfunction that is central to ALS pathogenesis.
Autophagy Dysregulation: Impaired DNAJC14 function disrupts autophagy, leading to accumulation of damaged proteins and organelles.
Stress Granule Dynamics: DNAJC14 may be involved in stress granule assembly and disassembly, processes that are perturbed in ALS.
DNAJC14-based therapeutic strategies for ALS include:
DNAJC14 alterations have been reported in Parkinson's disease:
Expression Changes: DNAJC14 expression is altered in PD brains and in models of dopaminergic degeneration.
α-Synuclein Interaction: DNAJC14 may interact with α-synuclein and influence its aggregation and clearance.
Genetic Studies: Some evidence links DNAJC14 variants to PD risk, though data are less extensive than for other genes.
ER Stress in Dopaminergic Neurons: Dopaminergic neurons are particularly sensitive to ER stress. DNAJC14 dysfunction exacerbates ER stress induced by α-synuclein and other PD-related proteins.
Mitochondrial Quality Control: DNAJC14 regulates mitochondrial protein quality control. Loss of DNAJC14 function contributes to mitochondrial dysfunction in PD.
Autophagy-Lysosome Pathway: DNAJC14 influences the autophagy pathway that is critical for clearing α-synuclein. Impaired function leads to α-synuclein accumulation[@liu2021].
DNAJC14 mutations have been associated with hereditary spastic paraplegia (HSP):
Gene Mutations: Rare DNAJC14 mutations cause a form of hereditary spastic paraplegia with additional neurological features.
Protein Quality Control: The mutations impair ERAD function, leading to accumulation of misfolded proteins in neurons.
Axonal Transport: DNAJC14 may be involved in axonal transport of proteins, and dysfunction contributes to axonal degeneration in HSP[@wang2021].
Some studies suggest DNAJC14 may be relevant to AD:
APP Processing: DNAJC14 influences amyloid precursor protein (APP) processing and may affect Aβ production.
ER Stress: DNAJC14 dysfunction contributes to ER stress that is a feature of AD pathogenesis.
Protein Quality Control: Impaired proteostasis is a hallmark of AD, and DNAJC14 contributes to this deficit[@chen2018].
| Partner | Interaction Type | Functional Role |
|---------|-----------------|-----------------|
| Hsp70 (HSPA1A) | J domain binding | Protein folding |
| BiP (HSPA5) | J domain binding | ERAD function |
| Hsp90 | Co-chaperone complex | Protein maturation |
| CHIP (STUB1) | Co-chaperone complex | Protein degradation |
| ERAD components | Substrate targeting | Retrotranslocation |
| α-Synuclein | Client binding | Aggregation control |
| SOD1 | Client binding | Aggregation control |
DNAJC14 is involved in multiple cellular pathways:
Unfolded Protein Response (UPR): DNAJC14 function is linked to all three UPR sensors (PERK, IRE1, ATF6). Chronic ER stress can overwhelm DNAJC14-mediated quality control.
Autophagy Pathways: DNAJC14 regulates autophagy through interactions with autophagy-related proteins.
Proteasome Pathway: DNAJC14 delivers substrates to the proteasome for degradation.
Apoptosis Pathways: DNAJC14 can influence cell death decisions in response to proteotoxic stress.
Hsp70 Modulators: Compounds that enhance Hsp70 activity indirectly improve DNAJC14 function.
ERAD Enhancers: Small molecules that enhance ERAD efficiency.
Proteostasis Stabilizers: Compounds that stabilize protein folding and prevent aggregation.
Gene Therapy: AAV-mediated DNAJC14 expression to enhance protein quality control.
Protein Delivery: Administration of recombinant DNAJC14 to enhance chaperone function.
Cell Therapy: Transplantation of cells engineered to express DNAJC14.
Phenotype: Dnajc14 knockout mice show:
Dnajc14 overexpression: Can protect against proteotoxic stress in models of neurodegeneration.
ALS models: DNAJC14 modulation affects disease progression in SOD1 and TDP-43 models.
PD models: DNAJC14 influences α-synuclein pathology in various models.
Study of DNAJC14 employs various approaches: