Designing antibodies against LRRK2-targeted tau epitopes.

Phosphorylation of the microtubule associated protein tau is an important modulator of its normal physiological functioning; however, it may also contribute to tau mis-folding and aggregation in neurodegenerative diseases, which are collectively termed tauopathies. As such, the investigations of tau phosphorylation and kinases that modify tau are important in trying to elucidate tau function and the mechanisms involved in the development of tauopathies. We have recently demonstrated that the putative tau kinase leucine-rich repeat kinase 2 is capable of phosphorylating tau at threonines 169 and 175 in vitro, and it has been previously shown that hyperphosphorylation at threonine 175 occurs in filamentous tau species from Alzheimer's brain tissue. These prior findings suggest that further studies of phosphorylation of tau at these epitopes may shed light on the pathogenesis of tauopathies. There is, however, a lack of tools available to analyze phosphorylation of tau at these sites. This study aimed to bridge that resource gap by generating monoclonal antibodies against tau phosphorylated at either threonine 169 or 175. While we did not succeed in generating a phospho-specific antibody, we did generate an antibody, MHT2, which is specific for human tau encompassing the threonine 169/175 epitope region. Immunostaining of transgenic rTg4510 mouse tissue as well as human tauopathy cases with MHT2 indicates that this antibody selectively detects cytoplasmic tau in the form of neurofibrillary tangles, and that it may have a further specificity pertaining to severity of disease progression, either because of phosphorylation or conformational bias.