Identification of Synaptic DGKθ Interactors That Stimulate DGKθ Activity

Lipids and their metabolic enzymes are a critical point of regulation for the membrane curvature required to induce membrane fusion during synaptic vesicle recycling. One such enzyme is diacylglycerol kinase theta (DGK theta), which produces phosphatidic acid (PtdOH) that generates negative membrane curvature. Synapses lacking DGK theta have significantly slower rates of endocytosis, implicating DGK theta as an endocytic regulator. Importantly, DGK theta kinase activity is required for this function. However, protein regulators of DGK theta's kinase activity in neurons have never been identified. In this study, we employed APEX2 proximity labeling and mass spectrometry to identify endogenous interactors of DGK theta in neurons and assayed their ability to modulate its kinase activity. Seven endogenous DGK theta interactors were identified and notably, synaptotagmin-1 (Syt1) increased DGK theta kinase activity 10-fold. This study is the first to validate endogenous DGK theta interactors at the mammalian synapse and suggests a coordinated role between DGK theta-produced PtdOH and Syt1 in synaptic vesicle recycling.

Automated summary

Lipids and their metabolic enzymes play a crucial role in regulating membrane curvature during synaptic vesicle recycling. This study identifies endogenous interactors of diacylglycerol kinase theta (DGK theta) and reveals a coordinated role between DGK theta-produced phosphatidic acid (PtdOH) and synaptotagmin-1 (Syt1) in synaptic vesicle recycling.