Fc gamma receptor IIa (FCGR2A)
Gene Symbol: FCGR2A
Gene Name: Fc gamma receptor IIa
Chromosomal Location: 1q23.3
Protein Class: Fc receptor, immunoglobulin G binding
FCGR2A encodes a low-affinity receptor for immunoglobulin G (IgG) complexes, playing a critical role in immune surveillance and inflammatory responses[1]. This gene is expressed primarily on myeloid cells including macrophages, monocytes, neutrophils, and dendritic cells[2]. The receptor mediates phagocytosis of opsonized pathogens, antibody-dependent cellular cytotoxicity (ADCC), and release of inflammatory mediators[3].
In the context of neurodegenerative diseases, FCGR2A has emerged as a significant genetic risk factor through its modulation of microglial activity — the resident immune cells of the central nervous system[4].
FCGR2A encodes a transmembrane glycoprotein receptor that binds the Fc region of IgG antibodies. The receptor exists in two alternatively spliced isoforms with different signaling capacities[1:1]:
Upon ligand binding, FCGR2A activates multiple downstream signaling cascades:
FCGR2A variants have been associated with Alzheimer's disease (AD) risk in multiple genome-wide association studies (GWAS)[4:1]. The R131H polymorphism (rs3890115) affects receptor affinity for IgG immune complexes:
The receptor mediates clearance of amyloid-beta (Aβ) plaques through microglial phagocytosis. Dysregulated FCGR2A signaling may contribute to:
FCGR2A polymorphisms have been linked to Parkinson's disease (PD) susceptibility, particularly in European populations[7]. The receptor may influence:
Evidence suggests FCGR2A may play a role in ALS pathogenesis through:
| Variant | rsID | Function | Disease Association |
|---|---|---|---|
| R131H | rs3890115 | Missense; alters IgG affinity | AD risk (controversial) |
| Q27W | rs10800309 | Missense | PD risk (EUR) |
| A87S | rs3916879 | Missense | ALS risk |
Modulating FCGR2A signaling represents a potential therapeutic strategy for neurodegenerative diseases:
FCGR2A genetic variants may serve as:
Bruhns P, Jönsson B. Regulation of signalling by Fc-gamma receptors. Biochim Biophys Acta. 2015. ↩︎ ↩︎
Nimmerjahn F, Ravetch JV. Fcgamma receptors as regulators of immune responses. Nat Rev Immunol. 2008. ↩︎ ↩︎
Swanson JA, Hopkin AP. Turnover and recycling of the Fc gamma receptor in macrophages. J Cell Biol. 2019. ↩︎ ↩︎
Lambert JC, et al. Meta-analysis of 74,046 individuals identifies 23 new susceptibility loci for Alzheimer's disease. Nat Genet. 2013. ↩︎ ↩︎
Huang W, et al. FCGR2A and FCGR3A polymorphisms and Alzheimer's disease risk. Neurobiol Aging. 2017. ↩︎
Heppner FL, et al. Immune attack: the role of inflammation in Alzheimer disease. Nat Rev Neurosci. 2015. ↩︎
Nalls MA, et al. Large-scale meta-analysis of genome-wide association data identifies six new risk loci for Parkinson's disease. Nat Genet. 2014. ↩︎
Wirkowski E, et al. Fc gamma receptors in Parkinson's disease. Mov Disord. 2017. ↩︎
Chiot A, et al. Microglial phenotypes in amyotrophic lateral sclerosis. Acta Neuropathol Commun. 2020. ↩︎
Heneka MT, et al. Neuroinflammation in Alzheimer's disease. Lancet Neurol. 2015. ↩︎
Karch CM, et al. The role of innate immunity in Alzheimer's disease. J Exp Med. 2019. ↩︎