Neuronal plasma membrane dynamics evoked by osmomechanical perturbations

Area of Science:

• Cell Biology
• Neuroscience
• Membrane Dynamics

Background:

• Neurons undergo significant plasma membrane reorganization during volume changes (swelling and shrinking).
• Vacuole-like dilations (VLDs) are transient structures observed during these processes, counterintuitively expanding as neurons shrink.

Purpose of the Study:

• To investigate the membrane topology and dynamics of VLDs during their formation, expansion, shrinkage, and recovery in cultured neurons.
• To elucidate the role of VLDs in neuronal plasma membrane surface area regulation.

Main Methods:

• Confocal microscopy was employed on cultured molluscan (Lymnaea) neurons.
• Aqueous phase and membrane dyes were used to track VLD membrane topology and dynamics.
• Washout experiments assessed the isolation of VLDs from the external medium.

Main Results:

• VLDs initiate as invaginations at the adherent neuronal surface, with contiguous VLD and plasma membranes.
• VLDs expand into the cytoplasm and subsequently shrink, leading to plasma membrane internalization via VLD mouth constriction.
• VLD constriction results in the formation of true vacuoles, and VLDs can be reversed by inducing neuronal swelling.

Conclusions:

• VLD formation and membrane reinternalization are key mechanisms for neuronal plasma membrane surface area regulation.
• These processes are likely driven by regional membrane tension differences when normal reprocessing steps are overloaded.
• Neuronal volume changes, particularly osmotic perturbations, trigger surface area adjustments mediated by VLD dynamics.