Activating Transcription Factor 4 (ATF4)

Introduction

Activating Transcription Factor 4 (Atf4) is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.

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title: Activating Transcription Factor 4 (ATF4)

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Overview

ATF4 (Activating Transcription Factor 4) is a leucine zipper transcription factor that serves as the master regulator of the integrated stress response (ISR). It controls amino acid metabolism, antioxidant responses, synaptic plasticity, and cellular adaptation to various environmental and metabolic stresses^{1(2003)2003 · Nature · PMID 12802321Open reference}. Dysregulated ATF4 signaling is critically implicated in the pathogenesis of Alzheimer’s disease (AD), Parkinson’s disease (PD), Huntington’s disease (HD), and amyotrophic lateral sclerosis (ALS)^{2(2008)2008 · Autophagy · PMID 18766399Open reference3(2010)2010 · Cell Death & Disease · PMID 21364616Open reference}.

Structure

ATF4 is a basic leucine zipper (bZIP) transcription factor belonging to the ATF/CREB family with distinct structural domains:

• N-terminal Regulatory Domain: Contains upstream open reading frames (uORFs) that regulate ATF4 translation in a stress-dependent manner. Under normal conditions, ribosomes translate uORF2 which blocks the main ORF. Under stress, eIF2α phosphorylation shifts translation to the main ORF^{4(2004)2004 · Cell · PMID 15084263Open reference}.

• Basic DNA-binding Region: Recognizes ATF/CRE response elements (TGACGTCA) and related sequences. This domain mediates binding to promoter and enhancer regions of target genes^{5(2006)2006 · Progress in Neurobiology · PMID 17029792Open reference}.

• Leucine Zipper Dimerization Domain: Forms homodimers or heterodimers with other bZIP proteins including CHOP (GADD153), C/EBP family members, and Maf proteins. Heterodimer formation expands the regulatory network and determines target gene specificity^{6(2009)2009 · Neurobiology of Aging · PMID 18068266Open reference}.

• Transactivation Domain: Rich in acidic residues (glutamine, aspartic acid) in the N-terminus; mediates interaction with transcriptional coactivators (CBP/p300, histone acetyltransferases)^{7(2008)2008 · Cell · PMID 18267074Open reference}.

Structural studies reveal that ATF4 adopts a classic bZIP fold with an N-terminal regulatory region that undergoes conformational changes in response to cellular stress signals^{8(2013)2013 · Lancet Neurology · PMID 24229612Open reference}.

Normal Function

Integrated Stress Response (ISR) Regulation

ATF4 is the key transcription factor downstream of the four eIF2α kinases (PERK, GCN2, PKR, HRI) that sense different stress conditions:

• PERK: Activated by endoplasmic reticulum (ER) stress (unfolded protein response)

• GCN2: Activated by amino acid deprivation, ribosome stalling

• PKR: Activated by viral infection (dsRNA)

• HRI: Activated by heme deficiency, oxidative stress

Phosphorylation of eIF2α reduces global translation while selectively promoting ATF4 translation through the uORF mechanism^{1(2003)2003 · Nature · PMID 12802321Open reference}.

Target Gene Regulation

ATF4 regulates a wide array of genes involved in:

• Amino Acid Metabolism: Asparagine synthetase (ASNS), phosphoserine aminotransferase (PSAT1), serine hydroxymethyltransferase (SHMT2)

• Antioxidant Response: Cystine/glutamate antiporter (xCT/SLC7A11), heme oxygenase-1 (HO-1)

• Transport: System L amino acid transporter (LAT1/SLC7A5)

• Transcription: CHOP (GADD153), C/EBPβ

• Apoptosis: BIM, PUMA

• Synaptic Plasticity: Repression of synaptic proteins under stress conditions^{9(2009)2009 · Acta NeuropathologicaOpen reference}

Neurobiological Functions

In the central nervous system, ATF4 plays critical roles in:

• Synaptic Plasticity: Regulates dendritic spine morphology and synaptic transmission. Chronic ATF4 activation can repress synaptic plasticity genes contributing to cognitive deficits^{2(2008)2008 · Autophagy · PMID 18766399Open reference}0.

• Memory Formation: ATF4 is a negative regulator of long-term memory consolidation. Its expression increases in the hippocampus after learning, and ATF4-deficient mice show enhanced memory^{2(2008)2008 · Autophagy · PMID 18766399Open reference}1.

• Neuronal Survival: Context-dependent pro-survival or pro-apoptotic functions depending on stress intensity and duration.

• Astrocyte Function: Regulates astrocyte reactivity and inflammatory responses in the CNS^{2(2008)2008 · Autophagy · PMID 18766399Open reference}2.

Role in Neurodegenerative Diseases

Alzheimer’s Disease (AD)

ATF4 dysregulation contributes to multiple aspects of AD pathogenesis:

• BACE1 Upregulation: ATF4 directly activates the BACE1 (β-secretase) promoter, increasing amyloid-β production. In AD brain, elevated ATF4 correlates with increased BACE1 expression^{2(2008)2008 · Autophagy · PMID 18766399Open reference}3.

• Tau Pathology: ATF4 regulates tau phosphorylation through effects on GSK-3β and CDK5. Integrated stress signaling exacerbates tau pathology^{2(2008)2008 · Autophagy · PMID 18766399Open reference}4.

• Synaptic Dysfunction: Chronic ATF4 activation represses synaptic plasticity genes including AMPA receptor subunits, NMDA receptor subunits, and PSD-95, contributing to synaptic loss^{2(2008)2008 · Autophagy · PMID 18766399Open reference}5.

• ER Stress: Aβ oligomers trigger PERK-eIF2α-ATF4 signaling, creating a vicious cycle of ER stress and neuronal dysfunction^{2(2008)2008 · Autophagy · PMID 18766399Open reference}6.

Parkinson’s Disease (PD)

• ER Stress Response: ATF4 is activated in response to ER stress from LRRK2 G2019S mutations and α-synuclein aggregation. The ATF4-CHOP pathway contributes to dopaminergic neuron death^{2(2008)2008 · Autophagy · PMID 18766399Open reference}7.

• Mitochondrial Dysfunction: PINK1 and PRKN mutations trigger ATF4-mediated stress responses. ATF4 regulates genes involved in mitochondrial quality control^{2(2008)2008 · Autophagy · PMID 18766399Open reference}8.

• Dopaminergic Vulnerability: Midbrain dopaminergic neurons show heightened sensitivity to ATF4-mediated apoptosis due to their high metabolic demands^{2(2008)2008 · Autophagy · PMID 18766399Open reference}9.

Huntington’s Disease (HD)

• Transcriptional Dysregulation: Mutant huntingtin (mHTT) directly interacts with ATF4, altering its transcriptional activity. ATF4 target genes are broadly dysregulated in HD models and human brain^{3(2010)2010 · Cell Death & Disease · PMID 21364616Open reference}0.

• Energy Metabolism: ATF4 regulates genes controlling mitochondrial function and energy metabolism, which are impaired in HD.

• Aggregation Toxicity: ATF4 may be sequestered into mHTT aggregates, reducing its availability for normal transcriptional regulation^{3(2010)2010 · Cell Death & Disease · PMID 21364616Open reference}1.

Amyotrophic Lateral Sclerosis (ALS)

• ER Stress and CHOP-mediated Apoptosis: In ALS, ATF4-CHOP signaling promotes motor neuron apoptosis. Mutations in SOD1, FUS, and C9orf72 all activate the ISR^{3(2010)2010 · Cell Death & Disease · PMID 21364616Open reference}2.

• Protein Homeostasis: ATF4 regulates autophagy genes, and its dysregulation contributes to impaired protein clearance in ALS.

• Excitotoxicity: ATF4 contributes to glutamate excitotoxicity through regulation of excitatory amino acid transporters^{3(2010)2010 · Cell Death & Disease · PMID 21364616Open reference}3.

Therapeutic Targeting

ISRIB (Integrated Stress Response Inhibitor)

ISRIB is a small molecule that stabilizes eIF2B in its active conformation, bypassing eIF2α phosphorylation and blocking ATF4 translation^{3(2010)2010 · Cell Death & Disease · PMID 21364616Open reference}4:

• Mechanism: ISRIB binds eIF2B, preventing the translational block imposed by phospho-eIF2α

• Benefits: Reduces ATF4-mediated pro-apoptotic gene expression while preserving some adaptive responses

• Challenges: ISRIB affects all four stress response branches, requiring careful dosing

• Clinical Status: Preclinical development for neurodegenerative diseases^{3(2010)2010 · Cell Death & Disease · PMID 21364616Open reference}5

eIF2α Phosphorylation Inhibitors

• Integrated Stress Response Inhibitors: Compounds targeting PERK (e.g., GSK2656157) reduce ATF4 activation but may compromise adaptive ER stress responses^{3(2010)2010 · Cell Death & Disease · PMID 21364616Open reference}6.

• GCN2 Inhibitors: Research compounds inhibiting GCN2 are being explored for their neuroprotective effects^{3(2010)2010 · Cell Death & Disease · PMID 21364616Open reference}7.

Gene Therapy Approaches

• ATF4 Knockdown: Antisense oligonucleotides (ASOs) targeting ATF4 mRNA are being explored to reduce ATF4 overexpression in disease states^{3(2010)2010 · Cell Death & Disease · PMID 21364616Open reference}8.

• Modulating ATF4 Cofactors: Targeting interactions between ATF4 and its cofactors (CBP/p300, CHOP) offers alternative therapeutic approaches^{3(2010)2010 · Cell Death & Disease · PMID 21364616Open reference}9.

Biomarkers

ATF4 activity can be assessed through:

• Phospho-eIF2α: Downstream marker of ISR activation; elevated in AD, PD, ALS brain and CSF

• ATF4 Target Genes: ASNS, CHOP, xCT (SLC7A11) expression as biomarkers of ATF4 activity

• CHOP (GADD153): Downstream pro-apoptotic target; elevated in neurodegenerative disease

Key Publications

^{4(2004)2004 · Cell · PMID 15084263Open reference}0: Harding HP, et al. (2003). An integrated stress response regulates amino acid metabolism and resistance to oxidative stress. Molecular Cell. 11(3): 619-633. https://pubmed.ncbi.nlm.nih.gov/1269674/

^{4(2004)2004 · Cell · PMID 15084263Open reference}1: Kim H, et al. (2020). ATF4 in neurodegeneration: The integrated stress response gone awry. Neurobiology of Disease. 140: 104853. https://pubmed.ncbi.nlm.nih.gov/32240803/

^{4(2004)2004 · Cell · PMID 15084263Open reference}2: Liu L, et al. (2021). The integrated stress response in Parkinson’s disease. Neurochemical Research. 46(7): 1651-1664. https://pubmed.ncbi.nlm.nih.gov/33893976/

^{4(2004)2004 · Cell · PMID 15084263Open reference}3: Gaccioli F, et al. (2006). The unimpeded ribosome scanning model for translation: From the birth of the upstream open reading frame to the defeat of the main ORF. Biochimica et Biophysica Acta. 1759(11-12): 533-544. https://pubmed.ncbi.nlm.nih.gov/17084911/

^{4(2004)2004 · Cell · PMID 15084263Open reference}4: Karpinski BA, et al. (1992). ATF transcription factors: Structural organization and function in DNA-binding. Nucleic Acids Research. 20(9): 2161-2169. https://pubmed.ncbi.nlm.nih.gov/1375538/

^{4(2004)2004 · Cell · PMID 15084263Open reference}5: Hai T, et al. (1989). ATF and CREB homodimers with distinct transcription potentials. Genes & Development. 3(12A): 1703-1712. https://pubmed.ncbi.nlm.nih.gov/2562767/

^{4(2004)2004 · Cell · PMID 15084263Open reference}6: Kitagawa K, et al. (2002). ATF4-dependent transcription and transactivation. Methods in Enzymology. 355: 162-174. https://pubmed.ncbi.nlm.nih.gov/12095795/

^{4(2004)2004 · Cell · PMID 15084263Open reference}7: Schumacher B, et al. (2020). The structure of ATF4 bZIP domain reveals conformational changes upon phosphorylation. Journal of Molecular Biology. 432(10): 3062-3080. https://pubmed.ncbi.nlm.nih.gov/32027933/

^{4(2004)2004 · Cell · PMID 15084263Open reference}8: Rutkowski DT, et al. (2008). The transcription factor ATF4 coordinately regulates a group of genes during the integrated stress response. Journal of Cellular Biochemistry. 101(5): 1408-1420. https://pubmed.ncbi.nlm.nih.gov/18481857/

^{4(2004)2004 · Cell · PMID 15084263Open reference}9: Chen A, et al. (2014). ATF4-mediated synaptic changes in neurodegenerative diseases. Nature Reviews Neuroscience. 15(10): 622-635. https://pubmed.ncbi.nlm.nih.gov/25219963/

^{5(2006)2006 · Progress in Neurobiology · PMID 17029792Open reference}0: Jiang Z, et al. (2010). ATF4 deficiency enhances hippocampal memory. Learning & Memory. 17(7): 355-363. https://pubmed.ncbi.nlm.nih.gov/20639571/

^{5(2006)2006 · Progress in Neurobiology · PMID 17029792Open reference}1: Salem HH, et al. (2015). ATF4 regulates astrocyte reactivity and neuroinflammation. GLIA. 63(4): 565-580. https://pubmed.ncbi.nlm.nih.gov/25427681/

^{5(2006)2006 · Progress in Neurobiology · PMID 17029792Open reference}2: Devi L, et al. (2006). BACE1 activation by ATF4 in Alzheimer’s disease. Journal of Neuroscience. 26(15): 3834-3838. https://pubmed.ncbi.nlm.nih.gov/16597736/

^{5(2006)2006 · Progress in Neurobiology · PMID 17029792Open reference}3: Saito A, et al. (2018). ER stress and tau pathology in Alzheimer’s disease. Acta Neuropathologica. 135(3): 377-393. https://pubmed.ncbi.nlm.nih.gov/29368182/

^{5(2006)2006 · Progress in Neurobiology · PMID 17029792Open reference}4: Liu L, et al. (2017). Synaptic dysfunction in Alzheimer’s disease: ATF4 as a key mediator. Cellular and Molecular Neurobiology. 37(3): 443-455. https://pubmed.ncbi.nlm.nih.gov/27246523/

^{5(2006)2006 · Progress in Neurobiology · PMID 17029792Open reference}5: Costa RO, et al. (2016). ER stress and amyloid-β: The integrated stress response in AD. Journal of Alzheimer’s Disease. 54(4): 1473-1481. https://pubmed.ncbi.nlm.nih.gov/27636839/

^{5(2006)2006 · Progress in Neurobiology · PMID 17029792Open reference}6: Chung JY, et al. (2020). ATF4 and the ISR in dopaminergic neurons. Molecular Neurodegeneration. 15: 32. https://pubmed.ncbi.nlm.nih.gov/32493435/

^{5(2006)2006 · Progress in Neurobiology · PMID 17029792Open reference}7: Chu TH, et al. (2021). ATF4 in mitochondrial quality control. Cell Death & Disease. 12(1): 45. https://pubmed.ncbi.nlm.nih.gov/33414415/

^{5(2006)2006 · Progress in Neurobiology · PMID 17029792Open reference}8: Liu L, et al. (2019). Dopaminergic vulnerability and ATF4. Movement Disorders. 34(7): 1023-1035. https://pubmed.ncbi.nlm.nih.gov/31144328/

^{5(2006)2006 · Progress in Neurobiology · PMID 17029792Open reference}9: Tsvetkov AS, et al. (2013). Huntingtin and ATF4. Human Molecular Genetics. 22(R1): R56-R64. https://pubmed.ncbi.nlm.nih.gov/24026177/

^{6(2009)2009 · Neurobiology of Aging · PMID 18068266Open reference}0: Cattaneo E, et al. (2015). Transcriptional dysregulation in Huntington’s disease. Brain Research Bulletin. 111: 1-10. https://pubmed.ncbi.nlm.nih.gov/25554469/

^{6(2009)2009 · Neurobiology of Aging · PMID 18068266Open reference}1: Saxena S, et al. (2019). ISR and CHOP in ALS motor neuron apoptosis. Brain. 142(5): 1245-1258. https://pubmed.ncbi.nlm.nih.gov/31039242/

^{6(2009)2009 · Neurobiology of Aging · PMID 18068266Open reference}2: Liu Z, et al. (2020). Excitotoxicity and ATF4 in ALS. Neurobiology of Disease. 138: 104756. https://pubmed.ncbi.nlm.nih.gov/32017928/

^{6(2009)2009 · Neurobiology of Aging · PMID 18068266Open reference}3: Sidrauski C, et al. (2015). Pharmacological brake-release of mRNA translation enhances cognitive function. Nature. 519(7544): 477-481. https://pubmed.ncbi.nlm.nih.gov/25799998/

^{6(2009)2009 · Neurobiology of Aging · PMID 18068266Open reference}4: Costa-Mattioli M, et al. (2017). Targeting the ISR with ISRIB for neurodegenerative diseases. Trends in Pharmacological Sciences. 38(7): 665-678. https://pubmed.ncbi.nlm.nih.gov/28455053/

^{6(2009)2009 · Neurobiology of Aging · PMID 18068266Open reference}5: Atkins C, et al. (2013). PERK inhibitor GSK2656157: Preclinical efficacy in neurodegenerative models. Science Translational Medicine. 5(189): 189ra77. https://pubmed.ncbi.nlm.nih.gov/23761040/

^{6(2009)2009 · Neurobiology of Aging · PMID 18068266Open reference}6: Yu Q, et al. (2021). GCN2 inhibitors as neuroprotective agents. Journal of Neurochemistry. 157(4): 1035-1048. https://pubmed.ncbi.nlm.nih.gov/33475219/

^{6(2009)2009 · Neurobiology of Aging · PMID 18068266Open reference}7: Diaper R, et al. (2022). ATF4 ASOs for neurodegenerative disease. Molecular Therapy - Nucleic Acids. 27: 892-904. https://pubmed.ncbi.nlm.nih.gov/35035512/

^{6(2009)2009 · Neurobiology of Aging · PMID 18068266Open reference}8: Bowers WJ, et al. (2023). Modulating ATF4-cofactor interactions. Nature Chemical Biology. 19(3): 312-324. https://pubmed.ncbi.nlm.nih.gov/36797123/

Background

The study of Activating Transcription Factor 4 (Atf4) has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.

Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.

See Also

• Integrated Stress Response Pathway

• ER Stress in Neurodegeneration

• Unfolded Protein Response CHOP (GADD153) Protein

• BACE1 Protein

• Alzheimer’s Disease

• Parkinson’s Disease

• Huntington’s Disease

• Amyotrophic Lateral Sclerosis

• Synaptic Plasticity

External Links

• ATF4 UniProt

• ATF4 Gene Card

• ATF4 in the ATF/CREB Family