因tau 蛋白代謝異常而造成的各式神經退化性疾病統稱為Taupathies，例如阿茲海默症病人的腦裡可發現tau這種微管相關蛋白有異常堆積並形成神經纖維纏結的現象。一般而言，細胞內運輸物的堆積(類澱粉前驅蛋白，tau，神經細絲蛋白)可視為退化神經細胞的常見現象之一，而一些研究也發現當tau蛋白表現量增高時，細胞內的運輸會受到影響，使得許多運輸物不當堆積。因此，研究微管上負責運輸的分子馬達和微管相關蛋白之間的關係是非常重要的。在這篇研究裡，我們利用秀麗隱桿線蟲來探討類tau蛋白PTL-1和主要負責神經軸突運輸的分子馬達－KIF1A/UNC-104兩者的關係。研究發現在沒有PTL-1的情況下，UNC-104往細胞體方向運輸時改變方向的次數增加且中途停頓不動的次數和野生型相比也明顯增加，證明UNC-104的運動性受到影響，而同樣的現象也可在UNC-104運輸物synaptobrevin-1觀察到。此外，UNC-104和PTL-1在神經的相同位置上表現甚至一起同步移動的現象進一步指出PTL-1可能會被UNC-104運輸，且分析出來的結果顯示PTL-1的運輸速度屬於快速型運輸。最後，我們用雙分子螢光互補技術發現線蟲體內PTL-1和UNC-104兩者間的確有交互作用存在。

Tauopathies include a broad range of neuropathological disorders that are based on defects in tau metabolisms. The microtubule-binding protein tau plays roles in Alzheimer’s disease in which tau accumulates in neurofibrillary tangles. In general, cargo accumulation (amyloid precursor protein, tau, neurofilaments) is a common observed phenomenon in degenerated neurons and it has been found that elevation of tau expression disrupts cargo transport, leading to cargo accumulation. Thus it seems to be important to investigate the interaction between microtubule-associated proteins and molecular motors. Here, we set out to investigate the interaction of tau/PTL-1 (Protein with Tau-Like repeats) and the major axonal transporter KIF1A/UNC-104 in Caenorhabditis elegans. In PTL-1 knock-out worms, the motility of UNC-104 is critically affected: more motor reversals for retrograde movements are observed and at the same time more pausing events for retrograde movements can be seen (compared to wildtype). Interestingly, similar behavior can be observed for UNC-104’s major cargo synaptobrevin-1 alone. Moreover, UNC-104 and PTL-1 co-localize and even co-migrate in the nervous system of living animals, suggesting that PTL-1 might be a cargo of UNC-104. Further motility analysis shows comparable fast transport rate of PTL-1. Last, we used bimolecular fluorescence complementation assay (BiFC) to test for interactions between PTL-1 and UNC-104 in the living worms. Indeed, using this novel assay (that can effortlessly replace the more complicated FLIM/FRET assay) we were able to identify interactions between these two proteins.

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