TRIM67 regulates exocytic mode and neuronal morphogenesis via SNAP47

Area of Science:

• Neuroscience
• Cell Biology
• Molecular Biology

Background:

• Neuronal morphogenesis requires significant plasma membrane expansion.
• Soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) mediate exocytosis, crucial for membrane dynamics.
• Synaptic exocytosis involves distinct modes like full-vesicle fusion (FVF) and kiss-and-run fusion (KNR), but these are undescribed in developing neurons.

Purpose of the Study:

• To characterize exocytic fusion modes during neuronal development in murine cortical neurons.
• To investigate the role of the E3 ubiquitin ligase TRIM67 in regulating these fusion events.

Main Methods:

• High-resolution imaging of individual exocytic events in developing neurons.
• Classification algorithms to distinguish different fusion modes based on fluorescence profiles.
• Biochemical assays to assess SNARE complex formation and the role of TRIM67 and SNAP47.

Main Results:

• Identified four distinct exocytic fusion modes: two FVF-like (membrane-inserting) and two KNR-like (non-membrane-inserting).
• Observed distinct fusion pore dynamics for each mode.
• FVF-like exocytosis provides sufficient membrane for neuronal morphogenesis.
• TRIM67 promotes FVF-like exocytosis by limiting SNAP47 incorporation into SNARE complexes.

Conclusions:

• Developing neurons exhibit diverse exocytic fusion modes, contributing to membrane expansion during morphogenesis.
• TRIM67 plays a key role in promoting membrane-inserting exocytosis by modulating SNARE complex composition.
• Understanding these mechanisms is vital for comprehending neuronal development and potential therapeutic targets.