A protease processing site is essential for prorenin sorting to the regulated secretory pathway

Area of Science:

• Cell Biology
• Endocrinology
• Molecular Biology

Background:

• Prorenin is a precursor to active renin, an enzyme critical for blood pressure regulation.
• Secretory cells utilize distinct pathways for constitutive and regulated secretion of proteins.
• The sorting of prorenin to regulated secretory pathways in pituitary cells remains incompletely understood.

Purpose of the Study:

• To investigate the mechanisms governing the sorting of human prorenin to dense core secretory granules.
• To elucidate the role of the prosegment and proteolytic processing in prorenin's regulated secretion pathway.

Main Methods:

• Utilized transfected mouse pituitary AtT-20 cells for studying protein sorting.
• Employed pulse-chase labeling techniques to track prorenin processing and secretion.
• Constructed and expressed prorenin mutants and fusion proteins to assess cleavage site importance.

Main Results:

• Regulated secretion of prorenin was blocked by deleting the prosegment, premature cleavage, or mutating the cleavage site.
• Exposure of cleavage sites within prorenin prosegment fusion proteins induced cleavage-dependent regulated secretion.
• Identified a critical role for protease cleavage events in prorenin sorting and secretion.

Conclusions:

• Proteolytic processing of the prorenin prosegment is a key determinant for its entry into the regulated secretory pathway.
• Specific Golgi-resident processing proteases are implicated in sorting proteins like prorenin to secretory granules.
• This study provides insights into the molecular mechanisms underlying regulated protein secretion.