Expression of Microtubule Associated Protein Tau in Mouse Pancreatic Islets Is Restricted to Autonomic Nerve Fibers.

Abstract

Evidence from clinical studies and basic research has shown a strong correlation between Alzheimer's disease (AD) and type 2 diabetes. Tau, a neuronal microtubule-associated protein, is hyperphosphorylated and aggregated into neurofibrillary tangles in the AD brain. However, the expression of tau in pancreas is under debate. We determined the expression of tau in mouse pancreas. We used western blots, immunoprecipitation, and immunohistochemical staining to analyze pancreatic expression of tau in mice. We found that neither total tau nor phosphorylated tau was detectable in the mouse pancreas by western blots. Immunostaining with pan tau antibodies R134d and Tau-5 revealed bright and dense varicosities in the pancreatic islets and the exocrine pancreas. These varicosities were immunoreactive to synapsin 1, a presynaptic marker which can outline autonomic nerve profiles in pancreas, exhibiting complete colocalization with tau. Importantly, endocrine cells in islets did not exhibit specific immunoreactivity to any of pan tau antibodies tested, nor did the exocrine cells. In the mouse pancreas, we found that tau is exclusively expressed in autonomic nerve fibers, but there is no detectable expression in endocrine cells in the islet.