Clinical Diagnosis of Alzheimer Disease
Proteome Sciences has perfected SRM technology for the quantitation of Tau phospho-peptides, one of the main components of Alzheimer disease (AD). Tau is believed to stabilize microtubules in cells and may play a role in regulating synaptic signaling.
Phosphorylation of Tau results in detachment from the cellular scaffold, followed by formation of tangles characteristic for AD pathology. Tau can be phosphorylated at over 30 specific sites. The pattern of Tau phosphorylation seems to correlate with severity of pathological progression of the AD.
“If we detect and quantify Tau phosphorylation at individual amino acids, we will be able to aid in clinical diagnostics and to stratify patients for clinical trials,” commented Ian Pike, Ph.D., COO, Proteome Sciences.
In collaboration with Professor Brian Anderton at King’s College London, Proteome Sciences progressively identified kinases responsible for the phosphorylation process and their unique sites. The team singled out the CK1 delta kinase to be an early player in the sequence of Tau phosphorylation.
While pursuing validation of this kinase as a therapeutic target for its internal drug discovery program, Proteome Sciences secures contract biomarker services with pharmaceutical partners. The company provides SRM-based assays for absolute quantitation of total Tau protein and its phosphorylation at 10 sites. Tau can be tested in brain tissue, cells, and, soon, in cerebrospinal fluid.
“Not all required phosphorylation sites could be measured accurately using antibodies, and some of the phosphorylation sites are only one amino acid apart. So we spent a lot of effort optimizing the transitions for a multiplexed SRM assay,” continued Dr. Pike.
“In some models Tau contains mutations that lose the required trypsin cleavage point, therefore, we used an alternative peptidase to generate target peptides. Furthermore, we optimized the assay to detect Tau in different cellular fractions.”
In early 2012, expert international workgroups convened by the Alzheimer’s Association and the National Institute on Aging, an agency of the U.S. National Institutes of Health, have expanded AD diagnostic guidelines to include Tau. Proteome Sciences works with clients to develop customized assays for other phosphorylation sites to support drug development.
“SRM is the ideal technology for this application, providing highly discriminating measurements and high sensitivity,” concluded Dr. Pike.