| Progranulin (PGRN) | |
|---|---|
| Gene | GRN |
| UniProt | P28799 |
| PDB | 2JYE |
| Mol. Weight | 63.5 kDa (full-length); secreted fragments: 6-25 kDa |
| Localization | Secreted, Lysosomes, Cytoplasm |
| Family | Progranulin family |
| Diseases | Frontotemporal Dementia, Amyotrophic Lateral Sclerosis, Alzheimer's Disease |
Progranulin is a secreted glycoprotein encoded by the GRN gene that functions as a crucial regulator of neuronal survival, lysosomal function, and immune response[1]. The protein has a molecular weight of 63.5 kDa in its full-length form and is processed into smaller granulins (6-25 kDa) that have distinct biological activities[2]. Progranulin is localized to multiple cellular compartments including the secretory pathway, lysosomes, and cytoplasm, where it participates in diverse cellular processes[3].
Haploinsufficiency caused by GRN mutations is one of the most common genetic causes of frontotemporal dementia (FTD), accounting for approximately 5-10% of all FTD cases and up to 20% of familial FTD[4]. Additionally, GRN mutations have been implicated in amyotrophic lateral sclerosis (ALS) and may modify Alzheimer's disease (AD) risk[5].
Progranulin supports neuronal health through multiple mechanisms:
A critical function of PGRN is its role in lysosomal homeostasis:
PGRN exerts immunomodulatory effects:
Most pathogenic GRN mutations lead to reduced protein levels through:
The 50% reduction in PGRN levels is sufficient to cause FTD, demonstrating haploinsufficiency mechanism.
Loss of functional PGRN leads to:
PGRN deficiency leads to TDP-43 (encoded by TARDBP) mislocalization:
GRN mutations cause TDP-43-positive FTD:
| FTD Subtype | Percentage of GRN Cases |
|---|---|
| Behavioral variant FTD | ~60% |
| Primary progressive aphasia | ~25% |
| Corticobasal syndrome | ~15% |
Some GRN mutations cause ALS:
GRN may modify AD risk:
Progranulin contains multiple functional domains:
| Domain | Description | Function |
|---|---|---|
| Signal peptide | N-terminus (1-18) | Secretion |
| Granulin repeats | 7.5 repeats (60-80 aa each) | Protease resistance, activity |
| Cysteine-rich regions | Between granulin repeats | Structural stability |
| N-glycosylation sites | Multiple sites | Secretion, stability |
The protein is processed by various proteases including:
Baker M, Mackenzie IR, Pickering-Brown SM, Gass J, Rademakers R, Lindholm C, Snowden J, Adamson J, Sadovnick AD, Rollinson S, et al. Mutations in progranulin cause tau-negative frontotemporal dementia linked to chromosome 17. Nature. 2006. ↩︎ ↩︎
Eriksen JL, Mackenzie IR. Progranulin: a new player in neurobiology. Journal of Neurochemistry. 2007. ↩︎ ↩︎ ↩︎
Chintapaludi M, Baloh RH. Progranulin in the pathogenesis of Alzheimer's disease and related dementias. Neurobiology of Aging. 2021. ↩︎ ↩︎
Götzl JK, Capell A, Haass C. Understanding GRN-linked FTD. Trends in Neurosciences. 2020. ↩︎ ↩︎ ↩︎
Minami SS, Min SW, Krabbe G, Wang C, Zhou Y, Asab M, Holtzman DM, Miller CA, Gan L. Progranulin deficiency promotes neuroinflammation and selectively increases adult hippocampal neurogenesis. Journal of Clinical Investigation. 2020. ↩︎ ↩︎
Paushter DH, Du H, Feng T, Hu F. The lysosomal function of progranulin. Immunobiology. 2018. ↩︎ ↩︎
Zhang Y, Chen X, Zong J. Progranulin: a key player in microglial function. Nature Reviews Neurology. 2019. ↩︎ ↩︎
Irwin DJ, Cairns NJ, Grossman M, Lee EB, Van Deerlin VM, Lee VM, Trojanowski JQ. Frontotemporal lobar degeneration: TDP-43 pathology and the role of GRN mutations. Acta Neuropathologica. 2019. ↩︎ ↩︎
Arrant AE, Roberson ED. Therapeutic strategies for progranulin-deficient FTD. Neuron. 2023. ↩︎ ↩︎
Rojas JC, Boxer AL. Biomarkers for progranulin-related frontotemporal dementia. Alzheimer's & Dementia. 2023. ↩︎ ↩︎
Rascovsky K, Hodges JR, Knopman D, Mendez MF, Kramer JH, Neuhaus J, van Swieten JC, Seelaar H, Dopper EG, Onyike CU, et al. Sensitivity of revised diagnostic criteria for the behavioural variant of frontotemporal dementia. Brain. 2011. ↩︎
Zhang H, Tan CF, Bell L, Takao M, Dickson DW, Bigio EH, Hatanpaa KJ, White CL 3rd, Mann DM, Forman MS, et al. ALS with or without FTD: a clinical and pathological continuum. Acta Neuropathologica. 2019. ↩︎
Sheng J, Su L, Xu Z, Zhu G. Progranulin polymorphisms and risk of Alzheimer's disease: a meta-analysis. Journal of Alzheimer's Disease. 2014. ↩︎
Nguyen AD, Nguyen TA, Zhang J, Devireddy S, Zhou P, Rigo F, et al. A progranulin-derived therapeutic antibody restores synaptic function. Science Translational Medicine. 2021. ↩︎
Evers BM, Rodriguez-Navas C, Tesla RJ, Pridgeon J, Sager RA, Wentworth A, et al. Lipid alterations and lysosomal dysfunction in progranulin-deficient neurons. Nature Communications. 2023. ↩︎
Burberry A, Wells MF, Limone F, Couto A, Smith KS, Santiana J, et al. TDP-43-targeted oligonucleotides for ALS. Nature Communications. 2016. ↩︎
Meeter LH, Dopper EG, Jiskoot LC, Sanchez-Valle R, Graff C, Benussi L, Ghidoni R, Pijnenburg YA, Borroni B, Laforce R Jr, et al. Plasma and CSF progranulin in genetic FTD. Neurology. 2016. ↩︎
van Swieten JC, Heutink P. Strategies for genetic testing in frontotemporal dementia. JAMA Neurology. 2011. ↩︎
Ahmed Z, Sheng J, Xu ZF, Maxwell DK, Donnelly K, Killick R, Lewis J, Hutton M, McGowan E, O'Brien WT, Liao Q, et al. Accelerated lipofuscino genesis and microglial activation in progranulin-deficient mice. Neurobiology of Aging. 2010. ↩︎
Evers BM, Jurgeit A, Koyuncu S, Andersen PM. Drosophila as a model for understanding progranulin function. Journal of Molecular Cell Biology. 2021. ↩︎