MRM-based Quantitation of SNAP-25 Protein Isoforms in Cells and Human Brain Samples

摘要

Neuronal signaling occurs via exocytosis of neurotransmitter molecules. Vesicle fusion is mediated by soluble-NSF-attachment receptor proteins (SNAREs). SNAP-25, a neuronal SNARE, is located at the presynaptic membrane (1). Because of its importance to brain function, SNAP-25 has been investigated and implicated in several human conditions such as schizophrenia, ADHD and cognition. (2,3) Previously, we have shown lower levels of SNAP-25 protein in some brain regions in schizophrenia (4). In vertebrates, SNAP-25 exists in two isoforms, the result of alternative splicing of exons 5a and 5b (5). The expression of SNAP25 isoforms is developmentally regulated and the A and B isoforms confer different properties to neurotransmitter release (6,7) and could therefore affect brain function in schizophrenia. Isoform expression, however, has been investigated almost exclusively at the mRNA level and, to our knowledge, never in humans. Thus, we have developed an MRM-based assay to quantify SNAP-25A and B in human brain homogenates.