Angiogenin (ANG) is a secreted ribonuclease originally identified as a potent angiogenic factor, but subsequently found to have critical functions in neuronal survival, stress response, and protein homeostasis. The protein is encoded by the ANG gene on chromosome 14q11.2 and is a member of the pancreatic ribonuclease family. While primarily studied in the context of cancer and angiogenesis, mutations in ANG have been strongly linked to amyotrophic lateral sclerosis (ALS) and Parkinson's disease.
The 147-amino acid secreted protein has evolved additional functions beyond its angiogenic activity, including neuroprotection, modulation of rRNA transcription, and stress granule formation. These functions are particularly relevant to neurodegenerative diseases where cellular stress responses are compromised.
- Protein Name: ANG - Angiogenin, Ribonuclease 5
- UniProt ID: P03950
- Gene: ANG
- Molecular Weight: ~14 kDa (147 amino acids)
- Protein Class: Secreted ribonuclease, Growth factor
- Tissue Expression: Liver, brain, endothelial cells, neurons
- Subcellular Localization: Secreted, can be internalized to nucleus
Angiogenin has a classic ribonuclease fold:
- Signal peptide: Targets secretion via classical pathway
- N-terminal region: Contains cell-binding and heparin-binding sites
- Central catalytic domain: RNase active site (His-13, Lys-40, His-114)
- C-terminal region: Nuclear localization signal, angiogenic domains
- Three conserved disulfide bonds: Stabilize structure
Despite having only ~35% sequence identity with RNase A, angiogenin retains catalytic activity, though with different substrate specificity and lower activity than pancreatic RNases.
Angiogenin has diverse biological activities:
- Angiogenesis: Induces blood vessel formation (original function)
- rRNA transcription: Promotes rRNA synthesis in nucleus (angiogenin internalization)
- Ribosomal RNA processing: Maintains nucleolar integrity
- Stress response: Incorporated into stress granules under stress
- Neuroprotection: Supports neuronal survival under stress
- Cell proliferation and differentiation: Multiple cellular effects
The neuroprotective functions of angiogenin are mediated through its ability to maintain protein synthesis capacity during stress and promote cell survival pathways.
- ALS gene: ANG mutations cause ~1-2% of familial ALS
- Loss of function: Mutant angiogenin has reduced activity
- Stress granule dynamics: Altered stress granule formation
- Motor neuron vulnerability: Impaired neuroprotection
- Risk factor: ANG variants associated with PD risk
- Neuroprotection: Angiogenin protects dopaminergic neurons
- Angiogenesis: May affect vascular supply to substantia nigra
- Alzheimer disease: Altered ANG expression in AD brain
- Peripheral neuropathy: Angiogenin in nerve regeneration
- Recombinant angiogenin: Potential neuroprotective therapy
- Small molecule activators: Enhance angiogenin function
- Gene therapy: Delivery of wild-type ANG
- ALS combination approaches: ANG with other neurotrophic factors
- Greenway MJ et al., ANG mutations in ALS (2006)
- Subramanian V et al., Angiogenin in neurodegeneration (2011)
- Kieran D et al., Angiogenin is neuroprotective in ALS (2008)