Progranulin acts as a shared chaperone and regulates multiple lysosomal enzymes

Area of Science:

• Biochemistry
• Molecular Biology
• Genetics

Background:

• Progranulin (PGRN) is a multifunctional protein implicated in lysosomal function.
• Mutations and insufficiency of PGRN are linked to lysosomal storage diseases, including Gaucher disease (GD).
• PGRN's role in lysosomal regulation was unexpectedly uncovered during inflammation research.

Purpose of the Study:

• To elucidate the molecular mechanisms of PGRN in regulating lysosomal storage diseases.
• To investigate the direct interaction between PGRN and the lysosomal enzyme beta-glucocerebrosidase (GCaase).
• To explore PGRN's potential role as a shared chaperone for multiple lysosomal enzymes.

Main Methods:

• Utilized PGRN null mice models to study Gaucher disease phenotypes.
• Identified GRN gene variants in Gaucher disease patients.
• Measured serum PGRN levels in Gaucher disease patients.
• Investigated the direct binding and chaperone activity of PGRN towards GCase and Cathepsin D (CSTD).

Main Results:

• PGRN null mice exhibited characteristic features of Gaucher disease.
• GRN gene variants were found in GD patients, with significantly lower serum PGRN levels.
• PGRN directly binds to and chaperones the lysosomal enzyme GCase, essential for GD.
• PGRN's C-terminal granulin E domain (Pcgin) mediates its interaction with GCase and CSTD.
• Evidence suggests PGRN functions as a shared chaperone for multiple lysosomal enzymes.

Conclusions:

• Progranulin (PGRN) is a critical regulator of lysosomal function and a chaperone for key lysosomal enzymes.
• PGRN's chaperone activity, particularly towards GCase, offers new insights into Gaucher disease pathogenesis.
• The findings suggest PGRN's broader role in maintaining lysosomal homeostasis and its potential as a therapeutic target for lysosomal storage diseases.