Human heparanase is localized within lysosomes in a stable form

Area of Science:

• Biochemistry
• Cell Biology
• Enzymology

Background:

• Heparanase is an endo-beta-D-glucuronidase enzyme crucial for heparan sulfate (HS) and extracellular matrix (ECM) degradation.
• Its activity is implicated in tumor metastasis, angiogenesis, inflammation, and autoimmunity.
• Subcellular localization of heparanase is critical for regulating its biological functions but remains undetermined.

Purpose of the Study:

• To investigate the subcellular localization of heparanase in different cell types.
• To determine the role of heparanase localization in regulating its enzymatic functions.
• To elucidate the pathway of heparanase transport and accumulation within cells.

Main Methods:

• Immunofluorescent staining and electron microscopy were used to examine heparanase localization.
• A heparanase cDNA fused to green fluorescent protein (GFP) construct was employed for live-cell imaging.
• Localization was assessed in three distinct cell types.

Main Results:

• Heparanase was found to be primarily localized within lysosomes and the Golgi apparatus.
• Live-cell imaging confirmed heparanase localization in acidic vesicles.
• The study identified a stable accumulation of heparanase within lysosomes.

Conclusions:

• Heparanase is synthesized, transported to the Golgi apparatus, and accumulates in lysosomes.
• Lysosomal localization suggests a role in HS turnover and potential confinement of extracellular enzymatic activity.
• This localization mechanism may limit uncontrolled heparanase activity, impacting metastasis and angiogenesis.