DETECTION OF TAU PROTEIN ISOFORMS AND THEIR MUTANTS BY KINESIN BASED MICROTUBULE GLIDING ASSAY

摘要

Tau proteins are neuronal microtubule associated protein (MAP), and are found to play crucial role in the axonal transport by controlling the dynamics of microtubules (MTs). Tau protein is now considered as a biomarker for neurodegenerative conditions, like Alzhimer's disease (AD). The MT- tau binding affinity varies according to the type of tau isoform and their degree of phosphorylation. We have utilized the kinesin motor protein based microtubule gliding system, to detect and differentiate tau proteins and their mutant. The density, landing rate and the velocity of MTs decorated with tau proteins and its mutant (P301L) have been determined. MT- kinesin based gliding assay is found to be sensitive in detecting tau mutation. Though it was possible to distinguish tau isoforms that differ in the number of binding repeats (3R and 4R), the same was not observed for the isoforms that differ in the length of projection domain (0N, 1N, 2N). This is an interesting result in contrast with the results obtain from bead assay based tau detection that can detect the difference of projection domain. We observe that the role of projection domain in the tau protein's binding function is much lesser when compared to the isoforms with different binding repeats in gliding assay. The landing rate and density had similar effect in spite of the difference in the length of the projection domain (+29, +39 or + 59 AA). The velocity of tau decorated MTs did not aid in bringing out the difference in tau types. Our ultimate aim being to realize on-chip tau detection, we plan to extend our research to other tau mutants and also to differentiate tau isoforms by varying the assay conditions and tau incorporation methods.