PPT1 selectively depalmitoylates GAP43 to regulate neuronal excitability and cognitive function.

Area of Science:

• Neuroscience
• Molecular Biology
• Biochemistry

Background:

• Palmitoylation is a key lipid modification regulating protein function in neurons.
• Growth-associated protein 43 (GAP43) is crucial for axonal development and synaptic plasticity, but its depalmitoylase remains unidentified.
• Understanding GAP43 regulation is vital for comprehending neural circuit function.

Purpose of the Study:

• To identify the depalmitoylase of GAP43.
• To investigate the role of palmitoyl-protein thioesterase 1 (PPT1) in GAP43 depalmitoylation.
• To examine the consequences of disrupted PPT1-GAP43 signaling on neuronal morphology, circuit function, and behavior.

Main Methods:

• Biochemical assays and structural modeling to analyze PPT1-GAP43 interaction.
• CRISPR-Cas9 technology to generate GAP43 point mutation (GAP43-PM) and PPT1-knockout (PPT1-KO) mouse models.
• Electrophysiology and behavioral tests to assess neuronal and network function.

Main Results:

• PPT1 directly interacts with GAP43 at Cys3 and Cys4, mediating its depalmitoylation.
• Disruption of PPT1-GAP43 interaction leads to GAP43 hyperpalmitoylation, excessive dendritic arborization, and aberrant growth cone expansion.
• PPT1-GAP43 pathway dysfunction results in enhanced glutamatergic transmission, hippocampal hyperexcitability, and cognitive deficits.

Conclusions:

• The PPT1-GAP43 depalmitoylation pathway is essential for maintaining neuronal circuit homeostasis.
• Dysfunction in this pathway contributes to neurodevelopmental disorders.
• Targeting the PPT1-GAP43 pathway offers a potential therapeutic strategy for related neurodevelopmental conditions.