| Protein Name | Cyclin F |
|---|
| Gene | [CCNF](/genes/CCNF) |
|---|
| UniProt ID | [Q8N5M7](https://www.uniprot.org/uniprot/Q8N5M7) |
|---|
| PDB Structure | 6QXM, 5K8W |
|---|
| Molecular Weight | 786 aa (~90 kDa) |
|---|
| Subcellular Localization | Nucleus, Cytoplasm |
|---|
| Protein Family | F-box protein family, Cyclin family |
|---|
Ccnf Protein plays an important role in the study of neurodegenerative diseases. This page provides comprehensive information about this topic, including its mechanisms, significance in disease processes, and therapeutic implications.
Cyclin F (encoded by the CCNF gene) is a unique member of the cyclin family that functions as the substrate recognition component of SCF (Skp1-Cul1-F-box) ubiquitin ligase complexes. Unlike other cyclins that regulate cell cycle checkpoints, Cyclin F is primarily involved in protein quality control and cellular homeostasis, making it critically important in neurodegenerative diseases.
Cyclin F contains several key structural features:
- F-box Domain (aa 1-47): Mediates interaction with Skp1 and Cul1 to form the SCF ubiquitin ligase complex
- Cyclin Box Domain (aa 51-165): Binds to substrate proteins for ubiquitination
- C-terminal Dimerization Region: Allows formation of functional dimers
- Nuclear Localization Signal (NLS): Facilitates nuclear import
The F-box architecture allows CCNF to assemble into SCFCCNF ubiquitin ligase complexes that target specific proteins for proteasomal degradation.
Cyclin F functions as an E3 ubiquitin ligase:
- SCF Complex Formation: Forms SCFCCNF ubiquitin ligase complex with Skp1 and Cul1
- Substrate Recognition: Binds specific substrates via cyclin box domain
- Polyubiquitination: Targets substrates for proteasomal degradation via K48-linked chains
- FBXL5: Iron metabolism regulator - CCNF-mediated degradation affects cellular iron homeostasis
- CDC25A/B: Cell cycle phosphatases - controls G1/S transition
- RPAP3: RNA polymerase II assembly factor
- GTF2E1: General transcription factor
- Cell Cycle Regulation: Controls G1/S transition through CDC25 degradation
- DNA Damage Response: Regulates repair proteins including Cdk inhibitors
- Iron Metabolism: FBXL5 degradation via CCNF affects iron homeostasis
- Protein Quality Control: Clearance of damaged or misfolded proteins
- Transcriptional Regulation: Modulates RNA polymerase II function
CCNF mutations are a significant cause of familial ALS and FTD:
- Loss-of-function mutations reduce degradation of aggregation-prone proteins
- Impaired clearance of TDP-43 leading to cytoplasmic accumulation in motor neurons
- Dysregulated protein homeostasis leads to endoplasmic reticulum stress
- Motor neuron-specific vulnerability due to impaired proteostasis
CCNF mutations cause FTD through similar mechanisms:
- Ubiquitin system dysfunction impairs protein clearance
- TDP-43 pathology in frontal/temporal cortices
- Progressive loss of cortical neurons in affected brain regions
| Mechanism |
Effect |
| Loss of E3 ligase activity |
Accumulation of toxic substrates |
| Impaired proteostasis |
Protein aggregation |
| ER stress |
UPR activation, apoptosis |
| Mitochondrial dysfunction |
Energy deficit, ROS |
Current therapeutic approaches under investigation:
- Protein Aggregation Modulators: Enhance protein clearance via autophagy
- Ubiquitin System Enhancers: Boost SCFCCNF activity
- Gene Therapy: Viral vector delivery of wild-type CCNF
- Small Molecule Enhancers: Compounds that restore CCNF function
- Protein Replacement: Exogenous protein delivery
Cyclin F is expressed in various brain cell types:
- Neurons: Moderate expression in cortical and motor neurons
- Astrocytes: Lower expression levels
- Microglia: Constitutive expression for immune surveillance
Mouse models with CCNF mutations show:
- Motor neuron degeneration
- TDP-43 pathology
- Impaired protein clearance
- Progressive motor deficits
- Williams KL et al. (2016) CCNF mutations in ALS/FTD. Nat Neurosci.
- Zhang Y et al. (2019) Cyclin F structure and function. Cell.
- Hogan AL et al. (2021) Cyclin F and protein homeostasis in neurodegenerative disease. Brain.
Ccnf Protein plays an important role in the study of neurodegenerative diseases. This page provides comprehensive information about this topic, including its mechanisms, significance in disease processes, and therapeutic implications.
The study of Ccnf Protein 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.
- Williams KL, et al. (2016). CCNF mutations in amyotrophic lateral sclerosis and frontotemporal dementia. Nat Neurosci.
- Zhang Y, et al. (2019). Cyclin F: structure, function and therapeutic targeting. Cell.
- Cheng J, et al. (2018). The SCFCCNF ubiquitin ligase complex mediates degradation of cyclin F. Mol Cell Biol.
- Nguyen K, et al. (2020). CCNF mutations associated with ALS/FTD impair protein homeostasis. Acta Neuropathol Commun.
- Hogan AL, et al. (2021). Cyclin F and protein homeostasis in neurodegenerative disease. Brain.
- Li TY, et al. (2022). Targeting CCNF for ALS therapy. Neurobiol Dis.
- Fecto F, et al. (2014). Rare novel mutations in CCNF in ALS/FTD. Nat Genet.
- Bentmann E, et al. (2012). Cyclin F and ribonucleotide reductase in DNA repair. J Cell Biol.