Neurofibrillary tangles (NFTs) composed of intracellular aggregates of tau protein are a key neuropathological feature of Alzheimer’s Disease (AD) and other neurodegenerative diseases, collectively termed tauopathies. The abundance of NFTs has been reported to correlate positively with the severity of cognitive impairment in AD. However, accumulating evidences derived from studies of experimental models have identified that NFTs themselves may not be neurotoxic. Now, many of tau researchers are seeking a “toxic” form of tau protein. Moreover, it was suggested that a “toxic” tau was capable to seed aggregation of native tau protein and to propagate in a prion-like manner. However, the exact neurotoxic tau species remain unclear. Because mature tangles seem to be non-toxic component, “tau oligomers” as the candidate of “toxic” tau have been investigated for more than one decade. In this topic, we will discuss our consensus of “tau oligomers” because the term of “tau oligomers” [e.g. dimer (disulfide bond-dependent or independent), multimer (more than dimer), granular (definition by EM or AFM) and maybe small filamentous aggregates] has been used by each researchers definition. From a biochemical point of view, tau protein has several unique characteristics such as natively unfolded conformation, thermo-stability, acid-stability, and capability of post-translational modifications. Although tau protein research has been continued for a long time, we are still missing the mechanisms of NFT formation. It is unclear how the conversion is occurred from natively unfolded protein to abnormally mis-folded protein. It remains unknown how tau protein can be formed filaments [e.g. paired helical filament (PHF), straight filament and twisted filament] in cells albeit in vitro studies confirmed tau self-assembly by several inducing factors. Researchers are still debating whether tau oligomerization is primary event rather than tau phosphorylation in the tau pathogenesis. Inhibition of either tau phosphorylation or aggregation has been investigated for the prevention of tauopathies, however, it will make an irrelevant result if we don’t know an exact target of neurotoxicity. It is a time to have a consensus of definition, terminology and methodology for the identification of “tau oligomers”.

This book presents essential studies and cutting-edge research results on tau, which is attracting increasing interest as a target for the treatment of Alzheimer's disease. Tau is well known as a microtubule-associated protein that is predominantly localized in the axons of neurons. In various forms of brain disease, neuronal loss occurs, with deposition of hyperphosphorylated tau in the remaining neurons. Important questions remain regarding the way in which tau forms hyperphosphorylated and fibrillar deposits in neurons, and whether tau aggregation represents the toxic pathway leading to neuronal death. With the help of new technologies, researchers are now solving these long-standing questions. In this book, readers will find the latest expert knowledge on all aspects of tau biology, including the structure and role of the tau molecule, tau localization and function, the pathology, drivers, and markers of tauopathies, tau aggregation, and treatments targeting tau. Tau Biology will be an invaluable source of information and fresh ideas for those involved in the development of more effective therapies and for all who seek a better understanding of the biology of the aging brain.

Covering the major classes of posttranslational modifications, Posttranslational Modification of Proteins is the first comprehensive treatment of this burgeoning area of proteome diversification.

Cyclin Dependent Kinase 5 provides a comprehensive and up-to-date collection of reviews on the discovery, signaling mechanisms and functions of Cdk5, as well as the potential implication of Cdk5 in the treatment of neurodegenerative diseases. Since the identification of this unique member of the Cdk family, Cdk5 has emerged as one of the most important signal transduction mediators in the development, maintenance and fine-tuning of neuronal functions and networking. Further studies have revealed that Cdk5 is also associated with the regulation of neuronal survival during both developmental stages and in neurodegenerative diseases. These observations indicate that precise control of Cdk5 is essential for the regulation of neuronal survival. The pivotal role Cdk5 appears to play in both the regulation of neuronal survival and synaptic functions thus raises the interesting possibility that Cdk5 inhibitors may serve as therapeutic treatment for a number of neurodegenerative diseases.

Alzheimers disease affects 6-10% of the elderly population, causing impairment in cognitive functions and significant disability in daily living for more than ten years. Neurofibrillary tangles, amyloid deposits and neuronal loss are the three hallmarks of Alzheimers disease. Due to insolubility of these unique structures in Alzheimer brain tissue, they were very difficult to study by usual biochemical methods in the past. Active research is now going on to elucidate the pathogenesis of Alzheimers disease. Major topics of neurobiological study of Alzheimers disease include the unraveling of the molecular mechanism of neurofibrillary tangle formation in neuronal and glial cells, the molecular processing of amyloid precursor protein in intracellular organella and in extra-cellular space, and the molecular mechanism of neuronal loss. The articles in this book were selected from contributions presented by leading scientists in this field at the international symposium which took place in Osaka in 2002. This publication is essential reading for all researchers, clinicians, basic and social scientists, neurologists and psychiatrists to promote the understanding of this formidable disease.

The editor of this volume, having research interests in the field of ROS production and the damage to cellular systems, has identified a number of enzymes showing ·OH scavenging activities details of which are anticipated to be published in the near future as confirmatory experiments are awaited. It is hoped that the information presented in this book on NDs will stimulate both expert and novice researchers in the field with excellent overviews of the current status of research and pointers to future research goals. Clinicians, nurses as well as families and caregivers should also benefit from the material presented in handling and treating their specialised cases. Also the insights gained should be valuable for further understanding of the diseases at molecular levels and should lead to development of new biomarkers, novel diagnostic tools and more effective therapeutic drugs to treat the clinical problems raised by these devastating diseases.