Functional organization of the sortilin Vps10p domain

Area of Science:

• Neuroscience
• Molecular Biology
• Cell Biology

Background:

• Sortilin is a neuronal receptor featuring a Vps10p domain.
• This domain binds various ligands like neurotrophins and neuropeptides.
• The Vps10p domain is characteristic of a family of neuronal receptors.

Purpose of the Study:

• To investigate the functional roles of two key structural features of Sortilin's Vps10p domain: the N-terminal propeptide and the C-terminal ten conserved cysteines (10CC) segment.
• To elucidate the mechanisms by which these features influence Sortilin's ligand binding and intracellular transport.

Main Methods:

• Module-shuffling experiments to analyze the 10CC segment.
• Truncation studies to assess the roles of the propeptide and 10CC segment.
• Analysis of Sortilin's processing and ligand binding during biosynthesis.

Main Results:

• The N-terminal propeptide of Sortilin has dual functions: preventing premature ligand binding and facilitating Golgi transport.
• Unlike other Vps10p receptors (SorLA, SorCS3), Sortilin's propeptide is essential for its processing.
• The 10CC segment acts as an exchangeable module and is identified as a primary ligand-binding region.

Conclusions:

• The N-terminal propeptide and 10CC segment are critical for Sortilin's function.
• Sortilin's propeptide plays a unique role in its biogenesis compared to related receptors.
• The 10CC segment is a key determinant of Sortilin's ligand-binding specificity.