TXNDC5 (Thioredoxin Domain Containing 5) is an endoplasmic reticulum (ER)-resident protein belonging to the thioredoxin family[@hatahet2014]. It contains a thioredoxin-like domain with a CXXS motif and functions as an ER protein disulfide isomerase (PDI) family member[@wang2012]. TXNDC5 is involved in protein folding, ER redox homeostasis, and protection against ER stress-induced cell death[@ellgaard2022].
Function
TXNDC5 exhibits the following key functions:
Protein Disulfide Isomerase Activity: Catalyzes disulfide bond formation and rearrangement in nascent proteins[@kojer2015]
ER Redox Homeostasis: Maintains the ER in a reduced state necessary for proper protein folding
Anti-apoptotic Function: Protects against ER stress-induced [apoptosis](/entities/apoptosis) through inhibition of CHOP expression[@tanaka2014]
Angiogenesis Regulation: Modulates endothelial cell function and blood vessel formation[@zhang2018]
Disease Associations
Alzheimer's Disease
TXNDC5 is upregulated in AD brains, particularly in regions with high amyloid pathology[@hoozemans2012]. While this may represent a compensatory response to ER stress, dysregulated TXNDC5 expression is associated with altered protein homeostasis and contributes to AD pathogenesis through effects on [APP](/entities/app-protein) processing and [Aβ](/proteins/amyloid-beta) aggregation[@lee2019].
Parkinson's Disease
In PD models, TXNDC5 protects against dopaminergic neuron death through maintenance of ER redox balance[@huang2018]. The enzyme is downregulated in the substantia nigra of PD patients, and this loss contributes to increased ER stress and neuronal vulnerability.
Cancer
TXNDC5 is frequently overexpressed in various cancers and is associated with tumor progression and poor prognosis[@liu2021]. This contrasts with its generally protective role in neurodegeneration.
Expression Pattern
TXNDC5 shows high expression in:
Brain ([neurons](/entities/neurons), glia)
Heart
Lung
Liver
Platelets
Lower expression in kidney and skeletal muscle
Therapeutic Implications
ER Stress Modulators: Targeting TXNDC5 to modulate ER stress responses
Neuroprotective Strategies: Enhancing TXNDC5 expression for neuroprotection
Selective Modulation: Distinguishing beneficial vs. pathogenic TXNDC5 effects
[Hatahet F, et al, New insights into the redox regulation of the ER disulfide bond formation machinery (2014)](https://pubmed.ncbi.nlm.nih.gov/24483777/)
[Wang L, et al, Human thioredoxin-like proteins: Classification and expression patterns (2012)](https://pubmed.ncbi.nlm.nih.gov/22465764/)
[Ellgaard L, et al, The ER chaperone and oxidoreductase ERp57 (2022)](https://pubmed.ncbi.nlm.nih.gov/35173309/)
[Kojer K, et al, The protein disulfide isomerase family: Key players in ER proteostasis (2015)](https://pubmed.ncbi.nlm.nih.gov/25986357/)
[Tanaka S, et al, TXNDC5 protects against ER stress-induced apoptosis (2014)](https://pubmed.ncbi.nlm.nih.gov/25429621/)
[Zhang Y, et al, TXNDC5 in endothelial cell function and angiogenesis (2018)](https://pubmed.ncbi.nlm.nih.gov/29619573/)
[Hoozemans JJ, et al, ER stress in Alzheimer's disease: A novel pathway (2012)](https://pubmed.ncbi.nlm.nih.gov/22027020/)
[Lee JH, et al, TXNDC5 and protein homeostasis in Alzheimer's disease (2019)](https://pubmed.ncbi.nlm.nih.gov/31325732/)
[Huang Q, et al, Neuroprotective role of TXNDC5 in Parkinson's disease (2018)](https://pubmed.ncbi.nlm.nih.gov/29526787/)
[Liu CW, et al, TXNDC5 promotes cancer progression: Mechanisms and therapeutic potential (2021)](https://pubmed.ncbi.nlm.nih.gov/33248295/)