Table 1.

Biological functions of α-syn protein

Proposed function	Mechanisms	Related interacting partners	References
Synaptic vesicle  regulation	Maintain vesicle reserves Reduce vesicle mobility Reduce vesicle docking via SNARE complex* Reduce neurotransmitter release*	Synaptophysin, synapsin I,  SNAP-25, synaptobrevin  2/VAMP2, VMAT2, CSPα	[98, 101–110]; [99, 100, 111]*
Mitochondrial  function	Inhibit fusion Promote fission Mitochondrial morphology	Unknown	[11, 112–118]
Ca2+ Homeostasis	Mitochondrial-ER Ca trafficking Mitochondrial anion channel regulation Cytosolic Ca2+ regulation	Calmodulin, mortalin/Grp75	[118–126]
DA handling	Increase DA reuptake* Increase DAT function* DAT membrane localization Tethering DAT to microtubules Increase VMAT on vesicles	DAT Tubulin VMAT	[110, 128, 130, 131]; [129, 132, 133]*; [134]*
DA biosynthesis	Reduce TH activity Reduce AADC activity	TH, PP2A AADC	[137–140]
Chaperone	Unknown Prevent aggregation	14-3-3 proteins DJ-1	[143–148]
Cytoskeletal function	Unknown (Vesicle transport)	Tubulin, tau, MAP1b, actin and  Rab small GTPases	[141, 142]
Protein  phosphorylation	Unknown (numerous possibilities)	ERK 1/2, PKC, CK1, MARK,  CaM Kinase II, PP1	[141–143]
Gene expression  (Nucleus)	Histone deacetylation Transcription regulation	Histones Promoters (e.g. PGC1-alpha, & others)	[149–151]
Lipid membranes	Unknown (Lipid metabolism)	Lipid rafts, Phospholipase D2	[153–156]