MAPT and Alzheimer disease: Increased amount of sulfated proteoglycans in AD brain [54], colocalisation with neurofibrillary tangles [29], and recently identified involvement of HSPGs in the process of tau neuronal internalization [27, 37, 57, 74, 84, 101] and tau secretion [46] are indicative of critical role of HSPGs in the transmission of tau pathology among neurons.