REG3A (Regenerating Family Member 3 Alpha), also known as HIP/PAP (Hepatocyte-Intestine-Pancreas/Reg III), is a secreted C-type lectin belonging to the Reg family of proteins. Initially characterized for its regenerative properties in pancreatic and hepatic tissues, emerging evidence suggests REG3A exerts neuroprotective effects in the central nervous system, making it a protein of interest in neurodegenerative disease research.
| Attribute | Value |
|---|---|
| Symbol | REG3A |
| Full Name | Regenerating Family Member 3 Alpha |
| Aliases | HIP, PAP, REG3 |
| Chromosomal Location | 2p12 |
| NCBI Gene ID | 64084 |
| Ensembl ID | ENSG00000138231 |
| UniProt ID | Q9NZU5 |
REG3A is a 175-amino acid secreted protein with a C-type lectin-like domain (CTLD) at its C-terminus. The protein forms a hexameric structure in solution, which is thought to facilitate its regenerative and protective functions[1]. Unlike classical C-type lectins that require calcium for carbohydrate binding, REG3A exhibits calcium-independent lectin activity, enabling stable interactions with bacterial cell wall peptidoglycans and potentially neuronal glycoconjugates[2].
REG3A participates in multiple biological processes:
REG3A has been shown to interact with amyloid-beta (Aβ) plaques in Alzheimer's disease models. In vitro studies demonstrate that REG3A can reduce Aβ-induced neurotoxicity by preventing Aβ oligomerization and facilitating its clearance[6]. The lectin domain may recognize specific glycans on Aβ aggregates, neutralizing their pathogenic effects.
REG3A modulates neuroinflammatory responses through inhibition of the NF-κB signaling pathway. In microglial cell models, REG3A treatment reduces production of pro-inflammatory cytokines including TNF-α, IL-1β, and IL-6[7]. This anti-inflammatory effect may be particularly relevant given the central role of chronic neuroinflammation in neurodegenerative disease progression.
Emerging evidence suggests REG3A activates autophagy in neuronal cells. Autophagy induction through mTOR-independent pathways promotes clearance of damaged mitochondria and protein aggregates, both hallmarks of neurodegeneration[8].
Following CNS injury, REG3A expression increases in neurons and glial cells. Functional studies demonstrate that exogenous REG3A promotes axonal regeneration through activation of the PI3K-Akt-mTOR signaling axis[9].
REG3A expression is downregulated in Alzheimer's disease brains, particularly in the hippocampus and temporal cortex[10]. This reduction correlates with disease severity, suggesting REG3A may serve a protective role that becomes compromised in AD. The protein's ability to neutralize Aβ and reduce neuroinflammation makes it a potential therapeutic target.
In Parkinson's disease models, REG3A has shown protective effects on dop protein appears to protect against mitochondrial dysfunction andaminergic neurons. The oxidative stress, both central to PD pathogenesis[11]. REG3A knockout mice exhibit increased vulnerability to MPTP-induced dopaminergic toxicity.
REG3A demonstrates protective effects in diabetic neuropathy models. Administration of REG3A improves nerve conduction velocities and reduces oxidative stress markers in peripheral nerves[12]. The mechanism involves activation of neurotrophic factor signaling and reduction of inflammatory demyelination.
REG3A expression increases following cerebral ischemia, suggesting a role in neuronal survival after stroke. Animal studies demonstrate that REG3A treatment reduces infarct size and improves functional recovery[13]. The neuroprotective effects involve anti-apoptotic signaling through Bcl-2 family proteins and reduction of excitotoxic damage.
Preliminary studies indicate altered REG3A expression in ALS models and patient tissue. The protein may modulate excitotoxicity and neuroinflammation in motor neuron disease, though mechanistic understanding remains incomplete[14].
| Tissue | Expression Level |
|---|---|
| Pancreas | Highest (islet cells) |
| Liver | High |
| Small Intestine | High (enterocytes) |
| Brain | Low to moderate |
| Spinal Cord | Low |
| Peripheral Nerve | Inducible |
REG3A expression is regulated by multiple factors:
The neuroprotective properties of REG3A have prompted investigation of recombinant protein as a therapeutic agent. Preclinical studies demonstrate that intravenous or intracerebroventricular administration of REG3A reduces pathology in AD and PD mouse models[15].
AAV-mediated REG3A overexpression represents an alternative therapeutic approach. Viral delivery of REG3A to the CNS achieves sustained protein expression and has shown efficacy in preclinical models of traumatic brain injury and neurodegenerative disease[16].
Identification of compounds that upregulate endogenous REG3A expression offers another therapeutic strategy. Natural compounds including curcumin and resveratrol have been shown to increase REG3A expression in neuronal cells[17].
Single nucleotide polymorphisms (SNPs) in the REG3A gene have been associated with:
The functional significance of these variants in neurodegeneration remains to be established.
Bertrand JA, et al. Crystal structure of human REG3A. Journal of Molecular Biology. 2013. ↩︎
Kitagawa N, et al. Structural basis of the calcium-independent lectin activity of REG3 proteins. Journal of Biological Chemistry. 2010. ↩︎
Liu H, et al. REG3A promotes β-cell proliferation through ERK1/2 signaling. Cellular and Molecular Gastroenterology and Hepatology. 2023. ↩︎
Cash HL, et al. Reg IIIγ: A gut-associated protein with antimicrobial activity. Gut Microbes. 2016. ↩︎
Sun J, et al. REG3A accelerates wound healing through promotion of epithelial cell migration. Scientific Reports. 2019. ↩︎
Wang X, et al. Neuroprotective effects of REG3A against amyloid-beta toxicity. Journal of Cellular Biochemistry. 2022. ↩︎
Chen L, et al. REG3A modulates neuroinflammation through NF-κB pathway inhibition. Journal of Neuroinflammation. 2022. ↩︎
Zhang Y, et al. REG3A induces autophagy in neuronal cells. Autophagy. 2021. ↩︎
Park J, et al. REG3A promotes axonal regeneration after CNS injury. Experimental Neurology. 2023. ↩︎
Zhou Q, et al. Downregulation of REG3A in Alzheimer's disease brains. Neurobiology of Aging. 2020. ↩︎
Kim S, et al. Protective effects of REG3A in Parkinson's disease models. Free Radical Biology and Medicine. 2022. ↩︎
Huang W, et al. REG3A ameliorates diabetic peripheral neuropathy. Diabetes. 2020. ↩︎
Li R, et al. REG3A neuroprotection in cerebral ischemia-reperfusion injury. Stroke. 2021. ↩︎
Rodriguez MJ, et al. Altered REG3A expression in amyotrophic lateral sclerosis. Brain Pathology. 2021. ↩︎
Xu P, et al. Therapeutic potential of recombinant REG3A in Alzheimer's disease mouse models. Alzheimer's Research & Therapy. 2022. ↩︎
Thompson HL, et al. AAV-mediated REG3A gene therapy promotes functional recovery after spinal cord injury. Molecular Therapy. 2023. ↩︎
Yang J, et al. Natural compounds upregulate REG3A expression in neuronal cells. Phytomedicine. 2022. ↩︎