The SAC1 phosphatase domain of synaptojanin‐1 is activated by interacting with polyunsaturated fatty acid‐containing phosphatidic acids

Abstract

Although there are many phosphatidic acid (PA) molecular species based on its fatty acyl compositions, their interacting partners have been poorly investigated. Here, we identified synaptojanin‐1 (SYNJ1), Parkinson’s disease‐related protein that is essential for regulating clathrin‐mediated synaptic vesicle endocytosis via dually dephosphorylating D5 and D4 position phosphates from phosphatidylinositol (PI) (4,5)‐bisphosphate, as a 1‐stearoyl‐2‐docosahexaenoyl (18:0/22:6)‐PA‐binding protein. SYNJ1 failed to substantially associate with other acidic phospholipids. Although SYNJ1 interacted with 18:0/20:4‐PA in addition to 18:0/22:6‐PA, the association of the enzyme with 16:0/16:0‐, 16:0/18:1‐, 18:0/18:0‐, or 18:1/18:1‐PA was not considerable. 18:0/20:4‐ and 18:0/22:6‐PAs bound to SYNJ1 via its SAC1 domain, which preferentially hydrolyses D4 position phosphate. Moreover, 18:0/20:4‐ and 18:0/22:6‐PA selectively enhanced the D4‐phosphatase activity, but not the D5‐phosphatase activity, of SYNJ1.

Docosahexaenoic acid-containing phosphatidic acid interacts with clathrin coat assembly protein AP180 and regulates its interaction with clathrin

“…After 18:0/22:6-PA-containing liposome precipitation from the mouse brain [ 17 ], liquid chromatography-tandem mass spectrometry identified the clathrin coat assembly protein AP180. The SCORE (probability of identification) and exponentially modified protein abundance index ( emPAI ) were 513 and 0.63, respectively ( Fig.…”

“…In the present study, 18:0/22:6-PA significantly attenuated clathrin assembly of AP180. We previously demonstrated that synaptojanin-1, which dephosphorylates PI(4,5)P 2 to detach AP180 from the membrane and acts as a main player in clathrin disassembly [ 31 ], is activated by 18:0/22:6-PA [ 17 ]. Therefore, it is possible that 18:0/22:6-PA produced by DGKδ effectively regulates clathrin disassembly through dual targets, AP180 and synaptojanin-1.…”

“…Liposome preparation by sonication was performed as described previously [ 16 ]. Liposomes with different diameters of 100 nm, 400 nm or 1000 nm were produced by a Mini Extruder (Avanti Polar Lipids) [ 17 ].…”

“…A liposome binding assay was carried out as described previously [ [16] , [17] , [18] ]. Purified 6His-tagged proteins (0.2 μM) were dissolved in HEPES buffer (25 mM HEPES, 100 mM NaCl, 1 mM DTT, pH 7.4) and incubated with liposomes at 4 °C for 30 min.…”

Presenting the FEBS Letters virtual issue on vesicle biology

“…In general, vesicles containing neurotransmitter fuse with the presynaptic cell to release neurotransmitter into the synaptic cleft. In their recent research article, the authors show that the SAC1 phosphatase domain of synaptojanin‐1 is activated by interaction with polyunsaturated fatty acids containing phosphatidic acids [10].…”