Plays a role in neurofilament network integrity. May be involved in modulating axonal architecture during development and in the adult. In vitro, increases the susceptibility of neurofilament-H to calcium-dependent proteases. May also function in modulating the keratin network in skin. Activates the MAPK and Elk-1 signal transduction pathway (By similarity). May be a centrosome-associated protein. Interacts with MYOC; affects its secretion and its aggregation. Associated with centrosomes in several interphase cells. In mitotic cells, localized to the poles of the spindle (By similarity). Highly expressed in brain, particularly in the substantia nigra. Also expressed in the corpus callosum, heart, skeletal muscle, ovary, testis, colon and spleen. Weak expression in pancreas, kidney and lung. Expressed predominantly in the cell bodies and axons of primary sensory neurons, sympathetic neurons and motoneurons. Developmentally expressed in primary sensory neurons and motoneurons. In trigeminal ganglia, expression increases between embryonic day 10 and day 12. High levels are maintained here throughout later stages of development and in adulthood. Phosphorylated. Phosphorylation by GRK5 appears to occur on residues distinct from the residue phosphorylated by other kinases (By similarity). Simultaneous knockout of SNCA, SNCB and SNCG exhibit an age-dependent decrease in SNARE-complex assembly. Thus, synucleins are required for maintaining normal SNARE-complex assembly during aging in mice. Belongs to the synuclein family.