Full Name: Signal Peptidase Like 2A (Intramembrane Aspartyl Protease)
Chromosome: 15q21.3
NCBI Gene ID: 84888
OMIM ID: 607260
Ensembl ID: ENSG00000119774
UniProt ID: Q8TDS0
| Full Name | Signal Peptidase Like 2A |
|---|---|
| Chromosome | 15q21.3 |
| NCBI Gene ID | [84888](https://www.ncbi.nlm.nih.gov/gene/84888) |
| OMIM | [607260](https://www.omim.org/entry/607260) |
| Ensembl ID | [ENSG00000119774](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000119774) |
| UniProt ID | [Q8TDS0](https://www.uniprot.org/uniprot/Q8TDS0) |
| Protein Class | Intramembrane aspartyl protease |
| Protein Size | 617 amino acids (~69 kDa) |
| Associated Diseases | [Alzheimer's Disease](/diseases/alzheimers-disease), [Parkinson's Disease](/diseases/parkinsons-disease), Immune Disorders |
| Expression | Ubiquitous: Brain, immune cells, kidney, liver |
SPPL2A (Signal Peptidase Like 2A) encodes an intramembrane aspartyl protease that catalyzes the proteolytic cleavage of type II membrane proteins within their transmembrane domains. This enzyme, also known as intramembrane-cleaving aspartic protease (I-CLiP), plays crucial roles in immune signaling, amyloid precursor protein (APP) processing, and has been increasingly implicated in the pathogenesis of neurodegenerative diseases including Alzheimer's disease and Parkinson's disease.
The discovery of SPPL2A expanded our understanding of regulated intramembrane proteolysis (RIP) as a fundamental cellular signaling mechanism. Unlike classical proteases that cleave substrates in aqueous environments, SPPL2A operates within the lipid bilayer, making it unique among enzymatic proteins involved in cellular signaling. This mechanism allows cells to generate bioactive fragments from membrane-bound precursors, enabling rapid responses to various stimuli.
The enzyme belongs to the signal peptide peptidase (SPP) family, which is evolutionarily conserved from bacteria to humans. SPPL2A shares structural features with other intramembrane proteases including presenilins (the catalytic component of gamma-secretase), but differs in substrate specificity and biological functions. The importance of SPPL2A in cellular homeostasis is underscored by the fact that knockout mice exhibit profound immune deficiencies, highlighting its essential role in immune system development and function.
SPPL2A is a member of the signal peptide peptidase (SPP) family of intramembrane proteases. Unlike traditional proteases that cleave substrates in aqueous environments, SPPL2A cleaves substrates within the lipid bilayer, making it unique among enzymatic proteins. This process, known as regulated intramembrane proteolysis (RIP), generates bioactive fragments that can function as signaling molecules or be further degraded.
SPPL2A contains the characteristic aspartyl protease motifs within its transmembrane domains:
SPPL2A processes multiple physiologically important substrates, making it a biologically significant enzyme in multiple pathways [1][2]:
The SPPL2A protein features several distinct domains:
SPPL2A plays a complex role in APP processing. Unlike beta-secretase (BACE1) which generates amyloid-beta peptides, SPPL2A cleaves APP at a different site, potentially generating non-amyloidogenic fragments. This alternative processing pathway has generated significant interest in SPPL2A as a potential therapeutic target for reducing amyloid-beta production [4][5].
The relationship between SPPL2A and AD involves several mechanisms:
SPPL2A is highly expressed in dopaminergic neurons of the substantia nigra, the brain region most affected in Parkinson's disease. Studies have revealed multiple connections between SPPL2A and PD pathogenesis [6][7][8]:
Given its role in processing TNF-alpha and Fas ligand, SPPL2A contributes significantly to neuroinflammatory processes relevant to multiple neurodegenerative diseases [1:1][10][11]:
SPPL2A is ubiquitously expressed with high levels in:
Within the brain, SPPL2A shows region-specific distribution:
SPPL2A has emerged as a potential therapeutic target for neurodegenerative diseases. However, its broad substrate specificity and essential roles in immune function present challenges for selective targeting.
Martinelli AH et al. SPPL proteases in health and disease. Trends Biochem Sci. 2020. ↩︎ ↩︎
Vonesh E, et al. SPPL2A substrate repertoire. Mol Cell Proteomics. 2016. ↩︎
Grimberg J, et al. SPPL2A-mediated CD74 cleavage. J Immunol. 2019. ↩︎
Mentrup T et al. SPPL2A and neurodegeneration. Cell Mol Neurobiol. 2019. ↩︎
Schmidt C, et al. SPPL2A in Alzheimer's disease. Acta Neuropathol. 2018. ↩︎
Zhang L, et al. SPPL2A genetic variants and Parkinson's disease. Mov Disord. 2021. ↩︎
Yang G, et al. SPPL2A and alpha-synuclein. Cell Death Dis. 2018. ↩︎
Liao R, et al. SPPL2A in dopaminergic neurons. J Neurosci. 2022. ↩︎
Stauten H, et al. SPPL2A and lysosomal function. Autophagy. 2019. ↩︎
Baranger K, et al. SPPL2A and immune response. J Neuroinflammation. 2016. ↩︎
Pan Y, et al. SPPL2A and neuroinflammation. Glia. 2020. ↩︎