α-Synuclein – Regulator of Exocytosis, Endocytosis, or Both?

α-Synuclein is known as a presynaptic protein that binds to small synaptic vesicles. Recent studies suggest that α-synuclein is not only attracted to these tiny and therewith highly curved membranes, but that in fact the sensing and regulation of membrane curvature is part of its physiological function. Moreover, recent studies have suggested that α-synuclein plays a role in the endocytosis of synaptic vesicles, and have provided support for a function of α-synuclein during exo- and endocytosis in which curvature sensing and membrane stabilization are crucial steps. This review aims to highlight recent research in the field and adds a new picture on the function of α-synuclein in maintaining synaptic homeostasis upon intense and repetitive neuronal activity.