SV2s (Synaptic Vesicle Protein 2) are integral membrane glycoproteins present in synaptic vesicles. They have 12 transmembrane domains predicted by sequence analysis (1). There are three characterized isoforms, SV2 A, SV2 B and SV2 C that are similar in structure but show different expression patterns. SV2 A is expressed ubiquitously throughout the brain and plays a crucial role in modulating synaptic transmission by regulating the expression and trafficking of synaptotagmin, a key calcium sensor in neurotransmitter release (1).
SV2 B has a more restricted distribution with varying degrees of coexpression with SV2 A and is predominantly found in the cortex and hippocampus (2). SV2 C is more closely related to SV2 A but shows a very restricted expression pattern. The highest expression levels were observed in phylogenetically old brain areas like pallidum, the midbrain and the olfactory bulb (3).
SV2 expression has also been observed in other non-neuronal organs. In kidney it localizes to podocytes and is essential for the integrity of the glomerular filtration barrier (4).