LAP3 - Leucine Aminopeptidase 3

LAP3 — Leucine Aminopeptidase 3

<div class="infobox infobox-gene">
<div class="infobox-header">LAP3</div>

Overview

LAP3 is a human gene whose product lAP3 (Leucine Aminopeptidase 3) is a cytosolic metalloexopeptidase that hydrolyzes N-terminal amino acids from peptides and proteins. It plays crucial roles in protein turnover, antigen processing, and peptide hormone metabolism. Variants in LAP3 have been implicated in Alzheimer's Disease, Parkinson's Disease, Cancer. This page covers the gene's normal function, disease associations, expression patterns, and key research findings relevant to neurodegeneration. [@liao2020]

LAP3 — Leucine Aminopeptidase 3

<div class="infobox infobox-gene">
<div class="infobox-header">LAP3</div>

Overview

LAP3 is a human gene whose product lAP3 (Leucine Aminopeptidase 3) is a cytosolic metalloexopeptidase that hydrolyzes N-terminal amino acids from peptides and proteins. It plays crucial roles in protein turnover, antigen processing, and peptide hormone metabolism. Variants in LAP3 have been implicated in Alzheimer's Disease, Parkinson's Disease, Cancer. This page covers the gene's normal function, disease associations, expression patterns, and key research findings relevant to neurodegeneration. [@liao2020]

<div class="infobox-row"><span class="infobox-label">Gene Symbol:</span><span class="infobox-value">LAP3</span></div>
<div class="infobox-row"><span class="infobox-label">Full Name:</span><span class="infobox-value">Leucine Aminopeptidase 3</span></div>
<div class="infobox-row"><span class="infobox-label">Chromosomal Location:</span><span class="infobox-value">4p14</span></div>
<div class="infobox-row"><span class="infobox-label">NCBI Gene ID:</span><span class="infobox-value">[51056](https://www.ncbi.nlm.nih.gov/gene/51056)</span></div>
<div class="infobox-row"><span class="infobox-label">Ensembl ID:</span><span class="infobox-value">ENSG00000002587</span></div>
<div class="infobox-row"><span class="infobox-label">UniProt ID:</span><span class="infobox-value">[Q9NYV5](https://www.uniprot.org/uniprot/Q9NYV5)</span></div>
<div class="infobox-row"><span class="infobox-label">Associated Diseases:</span><span class="infobox-value">[Alzheimer's Disease](/diseases/alzheimers-disease), [Parkinson's Disease](/diseases/parkinsons-disease), [Cancer](/diseases/cancer)</span></div>
</div>

Function

LAP3 (Leucine Aminopeptidase 3) is a cytosolic metalloexopeptidase that hydrolyzes N-terminal amino acids from peptides and proteins. It plays crucial roles in protein turnover, antigen processing, and peptide hormone metabolism.

Key Functions

• Protein Turnover: LAP3 participates in the degradation of misfolded and damaged proteins, working alongside the [proteasome](/mechanisms/ubiquitin-proteasome-pathway) and [lysosomal](/mechanisms/lysosomal-pathway) systems.
• Antigen Processing: The enzyme generates antigenic peptides for presentation via [MHC class I](/mechanisms/mhc-antigen-presentation) molecules, crucial for immune surveillance of abnormal cells.
• Peptide Hormone Metabolism: LAP3 processes bioactive peptides including [enkephalins](/proteins/enkephalin), [bradykinin](/proteins/bradykinin), and [angiotensin](/proteins/angiotensin), modulating neuropeptide signaling in the brain.
• Regulation of [Apoptosis](/entities/apoptosis): LAP3 interacts with [caspase](/proteins/caspase-3) pathways and can promote or inhibit [cell death](/mechanisms/apoptosis-neurodegeneration) depending on context.

Disease Associations

Alzheimer's Disease

LAP3 is implicated in AD through its role in [amyloid precursor protein](/entities/app-protein) (APP) processing and [Aβ peptide](/proteins/amyloid-beta) degradation. The enzyme can hydrolyze Aβ42, potentially reducing aggregation. However, altered LAP3 expression in AD brain may contribute to impaired peptide clearance.

Parkinson's Disease

In PD, LAP3 participates in [α-synuclein](/proteins/alpha-synuclein) degradation pathways. It may help clear aggregated [α-synuclein](/mechanisms/protein-aggregation) through proteolytic cleavage. Altered LAP3 activity could contribute to the accumulation of toxic protein aggregates.

Cancer

LAP3 is frequently overexpressed in various cancers including [glioblastoma](/diseases/glioblastoma). High LAP3 levels correlate with aggressive tumor growth and poor prognosis. The enzyme supports cancer cell proliferation and survival.

Molecular Mechanisms

LAP3 functions through several mechanisms:

Substrate Specificity

Key LAP3 substrates include:

• Aβ peptides: Amyloid-beta fragments (1-40, 1-42)
• α-synuclein: Toxic fragments of synuclein protein
• Enkephalins: Endogenous opioid peptides
• Cytokines: Pro-inflammatory peptide mediators

Expression

LAP3 is widely expressed in:

• Brain: [Cortex](/brain-regions/cortex), [hippocampus](/brain-regions/hippocampus), cerebellum
• Liver: Hepatocytes
• Kidney: Proximal tubules
• Immune cells: Macrophages, dendritic cells

• [Neurons](/cell-types/neurons)
• [Astrocytes](/cell-types/astrocytes)
• [Microglia](/cell-types/microglia)

• [Inflammatory cytokines](/mechanisms/cytokine-signaling)
• [Oxidative stress](/mechanisms/oxidative-stress)
• Cellular hypoxia

Therapeutic Implications

Drug Targets

LAP3 is a potential therapeutic target for:

• Inhibitors for cancer treatment (overexpressed in tumors)
• Activators for neuroprotection in AD/PD (enhance protein clearance)

Biomarkers

LAP3 expression levels may serve as a biomarker for:

• Glioblastoma prognosis
• Neurodegenerative disease progression

Research Models

In Vitro Models

• Cell lines: Neuronal cell lines (SH-SY5Y), glioblastoma cells
• Primary cultures: Primary neurons, astrocytes, microglia
• Cell-free systems: Purified LAP3 enzyme assays

In Vivo Models

• LAP3 knockout mice: Show altered peptide metabolism
• Transgenic models: Overexpression in specific tissues
• Xenografts: Human glioblastoma models

Experimental Approaches

• Enzyme activity assays (fluorometric, colorimetric)
• Proteomics for substrate identification
• Immunohistochemistry for localization
• siRNA/shRNA knockdown studies

Family Relationships

LAP3 belongs to the M17 family of metalloaminopeptidases:

• LAP3: Cytosolic leucine aminopeptidase
• LAP4 (CD13/ANPEP): Membrane-bound aminopeptidase N
• LAP5 (LPO): Leukocyte peptidase
• LAP6: Lysosomal aminopeptidase

Cross-References

• [Proteasome Pathway](/mechanisms/ubiquitin-proteasome-pathway)
• [Lysosomal Pathway](/mechanisms/lysosomal-pathway)
• [Protein Quality Control](/mechanisms/protein-quality-control-network)
• [Apoptosis Pathway](/mechanisms/apoptosis-neurodegeneration)

See Also

• [ Protein](/proteins/enkephalin)
• [Alzheimer's Disease](/diseases/alzheimers-disease)
• [Parkinson's Disease](/diseases/parkinsons-disease)
• [Cancer](/diseases/cancer)
• [proteasome](/mechanisms/ubiquitin-proteasome-pathway)
• [lysosomal](/mechanisms/lysosomal-pathway)
• [MHC class I](/mechanisms/mhc-antigen-presentation)
• [cell death](/mechanisms/apoptosis-neurodegeneration)

External Links

• [NCBI Gene: 51056](https://www.ncbi.nlm.nih.gov/gene/51056)
• [Ensembl: ENSG00000002587](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000002587)
• [UniProt: Q9NYV5](https://www.uniprot.org/uniprot/Q9NYV5)

References