| Property | Value |
|---|---|
| Protein Name | Progranulin |
| Gene | GRN |
| UniProt ID | P28799 |
| Molecular Weight | ~90 kDa (secreted); 68 kDa (granulin domain) |
| Subcellular Localization | Secreted; also localizes to lysosomes |
| Protein Family | Granulin family |
| Tissue Expression | Highest in brain (neurons, microglia), immune cells |
Progranulin is a secreted glycoprotein encoded by the GRN gene that functions as a multifunctional growth factor and regulator of lysosomal function[1]. It plays critical roles in neuronal survival, wound healing, inflammation, and protein homeostasis. Heterozygous loss-of-function mutations in GRN cause frontotemporal dementia (FTD), making it one of the most common genetic causes of this disorder. The protein is also implicated in Alzheimer's disease, Parkinson's disease, and lysosomal storage disorders[2].
Progranulin is unique among neurodegenerative disease proteins in that it functions as a secreted signaling molecule with both protective and pathological roles depending on context. The protein contains multiple granulin domains that can be proteolytically cleaved to generate small granulin peptides with distinct biological activities.
Progranulin contains several distinct structural features[2:1]:
The full-length protein (~90 kDa) can be cleaved by various proteases to generate granulin peptides (6-25 kDa), including:
Progranulin processing is regulated by several proteases:
| Protease | Cleavage Site | Functional Impact |
|---|---|---|
| Elastase | Multiple sites | Generates granulin peptides |
| MMP-9 | After granulin repeats | Produces active fragments |
| ADAMTS-4 | N-terminal | Regulates signaling |
| Cathepsin D | Lysosomal | Generates intracellular granulin |
The balance between full-length progranulin and granulin peptides determines downstream functions, as these species have distinct receptor interactions and biological activities.
Progranulin supports neuronal health through multiple mechanisms[3]:
A critical function of progranulin is its role in lysosomal biology[3:1]:
Progranulin deficiency leads to enlarged lysosomes with impaired cathepsin activity, accumulating lipofuscin, and disrupted autophagy flux.
Progranulin modulates immune responses:
Beyond the nervous system, progranulin functions in:
GRN mutations are a major cause of familial FTD[1:1]:
Genetic Basis:
Pathological Mechanisms:
Clinical Phenotype:
Progranulin has complex relationships with AD pathogenesis:
Emerging evidence links progranulin to PD:
Several approaches target progranulin pathways[3:2]:
| Strategy | Approach | Status |
|---|---|---|
| Protein replacement | Recombinant progranulin | Preclinical |
| Gene therapy | AAV-GRN | Phase 1/2 trials |
| Small molecules | Increase GRN expression | Discovery |
| Protease inhibitors | Block granulin generation | Research |
Baker M, et al. Mutations in GRN cause frontotemporal dementia. Nature. 2006. ↩︎ ↩︎
He Z, et al. Progranulin in neurodegenerative disease. Nature Reviews Neurology. 2022. ↩︎ ↩︎
Gass J, et al. Progranulin and lysosomal function in FTD. Acta Neuropathologica. 2024. ↩︎ ↩︎ ↩︎