Synapsins

Peripheral synaptic vesicle proteins; substrate for several protein kinases

General Information

Synapsins are neuron-specific phosphoproteins that are exclusively associated with small synaptic vesicles, with little or no expression in other tissues including neuroendocrine cells. Synapsin 1 is probably the most specific marker of synapses throughout the central and peripheral nervous system. In addition to synaptic nerve terminals, the protein is also present in certain sensory nerve endings.
Synapsin 1 is expressed in two splicing variants (synapsin 1a and synapsin 1b). In addition, a second related gene (synapsin 2) is expressed in the nervous system also resulting in two splicing variants. Synapsin 1 interacts with vesicle membranes as well as with actin and spectrin.
Synapsins are major phosphoproteins and are substrates for several protein kinases such as PKA, CaMK I and CaMK II. For instance, synapsin 1 is widely used as reference substrate for calmodulin-dependent protein kinases.