Yop1 stability and membrane curvature generation propensity are controlled by its oligomerisation interface

Area of Science:

• Cell Biology
• Biophysics
• Genetics

Background:

• DP1 proteins are integral membrane proteins crucial for stabilizing high membrane curvature in cellular structures like the endoplasmic reticulum and phagophores.
• Mutations in the human DP1 gene (REEP1) are linked to neurological disorders: Hereditary Spastic Paraplegia type 31 and distal hereditary motor neuropathy.
• Four missense mutations in REEP1 are located at a potential dimerization interface, but their effects on DP1 protein structure and function remain unclear.

Purpose of the Study:

• To investigate the impact of missense mutations on DP1 dimer structure, stability, and membrane tubulation activity.
• To elucidate the mechanistic role of DP1 oligomerization in membrane curvature stabilization.
• To understand how specific mutations affect DP1's ability to form and stabilize curved membrane structures.

Main Methods:

• Utilized a combination of biophysical measurements to assess protein structure and interactions.
• Employed functional assays to evaluate in vitro tubulation activity and membrane curving capabilities.
• Applied computational modeling to analyze the effects of mutations on DP1 dimer structure and oligomerization.

Main Results:

• Missense mutations exhibited variable effects on DP1 dimer structure and in vitro tubulation.
• Mutations P71L and S75F reduced dimer homogeneity, leading to polydisperse oligomerization and impaired membrane curving.
• Mutation A72E stabilized the Yop1 dimer through new polar interactions, enhancing tubule formation but hindering the creation of highly curved lipoprotein particles (LPPs).
• Introducing a BRIL domain to the A72E mutant rescued LPP formation, suggesting a need for dimer splaying in highly curved membranes.

Conclusions:

• DP1 protein function in membrane curvature stabilization is dependent on both dimer stability and conformational plasticity at the intermolecular interface.
• Specific mutations can disrupt the delicate balance between dimer stability and flexibility, leading to altered membrane shaping capabilities.
• Understanding these structure-function relationships is critical for deciphering the molecular basis of DP1-associated neuropathies.