VAP-mediated membrane-tethering mechanisms implicate ER-PM contact function in pH homeostasis

Area of Science:

• Cell Biology
• Membrane Trafficking
• Molecular Interactions

Background:

• Vesicle-associated membrane proteins (VAPs) are conserved ER proteins that mediate membrane contact sites.
• Mechanisms of VAP-mediated membrane tethering are not fully understood.
• ER-plasma membrane (PM) contacts are vital for cellular functions.

Purpose of the Study:

• To elucidate the mechanism of ER-PM contact formation mediated by VAPs in fission yeast.
• To investigate the role of VAP-phospholipid interactions in ER-PM tethering.
• To explore the functional significance of VAP-Pma1 interactions in pH homeostasis.

Main Methods:

• Systematic interactome analyses.
• Quantitative microscopy.
• Biochemical assays to study VAP-phospholipid and VAP-Pma1 interactions.

Main Results:

• ER-PM coupling is predicted to be independent of direct VAP-protein binding.
• VAP interactions with anionic phospholipids underlie ER-PM association and are pH-responsive.
• Amyotrophic lateral sclerosis-associated VAPB mutants show defective phospholipid interactions.
• A conserved motif in Pma1 interacts with VAP, crucial for pH homeostasis.

Conclusions:

• VAP-mediated ER-PM contacts are regulated by VAP-anionic phospholipid interactions.
• These interactions are conserved and functionally relevant, with implications for neurodegenerative diseases.
• VAP-Pma1 interaction provides a mechanism for pH sensing and regulation at the ER-PM interface.