PICCOLO, A NOVEL 420 KDA PROTEIN ASSOCIATED WITH THE PRESYNAPTIC CYTOMATRIX

In this study we describe a novel 420 kDa protein, called Piccolo, fou nd at a wide variety of adult rat brain synapses. High protein levels in the cerebellum, the olfactory bulb and the hippocampus were frequen tly observed to be associated with asymmetric type 1 synapses. Piccolo is selectively enriched in presynaptic terminals, but is not a compon ent of synaptic vesicles (SVs). Immunogold electron microscopy reveale d that Piccolo localizes to the amorphous material among SVs at the pr esynaptic plasma membrane. Biochemical studies showed that it is very tightly bound to this structure. Thus, we speculate that Piccolo is a structural component of the presynaptic cytomatrix which anchors SVs t o the presynaptic plasmalemma.