Synaptogyrins are tyrosine-phosphorylated proteins with two neuronal (synaptogyrin 1 and 3) and one ubiquitous, synaptogyrin 2 or cellugyrin isoform.
Synaptogyrins are integral membrane proteins and localize to the membrane of small vesicles. Synaptogyrin 1 and 3 are expressed in the brain whereby the latter shows a more restricted expression pattern with high levels in the mossy fiber region of the hippocampus, substantia nigra pars reticulata, pallidum, and deep cerebellar nuclei.
Synaptogyrin 2/cellugyrin, a close relative, is expressed in all tissues, for instance, in distinct populations of GLUT 4 containing vesicles.