Researchers seeking problems that offer more hope of success often avoid subjects that seem to be difficult to approach experimentally, or subjects for which experimental results are difficult to interpret. The breakdown part of protein turnover in vivo, particularly in nervous tissue, was such a subject in the past – it was difficult to measure and difficult to explore the mechanisms involved. For factors that influence protein metabolism, it was thought that protein content, function, and distribution are controlled only by the synthetic mechanisms that can supply the needed specificity and response to stimuli. The role of breakdown was thought to be only a general metabolic digestion, elimination of excess polypeptides. We now know that the role of breakdown is much more complex: it has multiple functions, it is coupled to turnover, and it can affect protein composition, function, and synthesis. In addition to eliminating abnormal proteins, breakdown has many modulatory functions: it serves to activate and inactivate enzymes, modulate membrane function, alter receptor channel properties, affect transcription and cell cycle, form active peptides, and much more. The hydrolysis of peptide bonds often involves multiple steps, many enzymes, and cycles (such as ubiquination), and often requires the activity of enzyme complexes. Their activation, modification, and inactivation can thus play an important role in biological functions, with numerous families of proteases participating. The specific role of each remains to be elucidated.

It is now well known that proteases are found everywhere, in viruses and bacteria as well as in all human, animal and plant cells, and play a role in a variety of biological functions ranging from digestion, fertilization, development to senescence and death. Under physiological conditions the ability of proteases is regulated by endogenous inhibitors. However, when the activity of proteases is not regulated appropriately, disease processes can result, as seen in Alzheimer’s disease, cancer metastasis and tumor progression, inflammation and atherosclerosis. Thus it is evident that there is an absolute need for a tighter control of proteolytic activities in different cells and tissues. Aimed at graduate students and researchers with an interest in cellular proteolytic events, Role of Proteases in Cellular Dysfunctions is the second book on Proteases in this series. The book consists of three parts in specified topics based on current literatures for a better understanding for the readers with respect to their subject-wise interests. The first section of this book covers a brief idea about the neuronal disorders and the involvement of proteases such as calpains, caspases and matrix metalloproteases (MMPs). The second section covers the deadly disease cancer and its relation to ubiquitin-proteasome system, MMPs and serine proteases. The last section is about the role of proteases such as calpains, MMPs and serine protease as well as urokinase type plasminogen activator receptor (uPAR) in causing cardiovascular defects.

Using a multidisciplinary approach, this book describes the biochemical mechanisms associated with dysregulation of proteases and the resulting pathophysiological consequences. It highlights the role and regulation of different types of proteases as well as their synthetic and endogenous inhibitors. The role of proteases was initially thought to be limited to general metabolic digestion. However, we now know that the role of protein breakdown is much more complex, and proteases have multiple functions: they are coupled to turnover and can affect protein composition, function and synthesis. In addition to eliminating abnormal proteins, breakdown has many modulatory functions, including activating and inactivating enzymes, modulating membrane function, altering receptor channel properties, affecting transcription and cell cycles and forming active peptides. The ubiquity of proteases in nature makes them an important target for drug development. This in-depth, comprehensive is a valuable resource for researchers involved in identifying new targets for drug development. With its multidisciplinary scope, it bridges the gap between fundamental and translational research in the biomedical and pharmaceutical industries, making it thought-provoking reading for scientists in the field.

In recent years, powered by evolving technologies and experimental design, studies have better illuminated the regulating role of proteolytic enzymes across human development and pathologies. Proteolytic Signaling in Health and Disease provides an in-depth discussion of fundamental physiological and developmental processes regulated by proteases, from protein turnover and autophagy to antigen processing and presentation and major histocompatibility complex (MHC) molecules. Moving on from basic biology, international chapter authors examine a range of pathological conditions associated with proteolysis, including inflammation, wound healing, and cancer. Later chapters discuss the newly discovered network of connected events among proteases (and their inhibitors), the so-called ‘protease web’, and how best to study it. This book also empowers new research with up-to-date analytical methods and step-by-step protocols for studying proteolytic signaling events. Examines biological events triggered by proteolytic enzyme activity across human development and pathologies Discusses the role of proteolytic signaling in inflammation, wound healing, and cancer, among other disease types Features methods and protocols supporting further study of proteolytic signaling events Includes chapter contributions from international leaders in the field

Proteolysis is an irreversible posttranslational modification affecting each and every protein from its biosynthesis to its degradation. Limited proteolysis regulates targeting and activity throughout the lifetime of proteins. Balancing proteolysis is therefore crucial for physiological homeostasis. Control mechanisms include proteolytic maturation of zymogens resulting in active proteases and the shut down of proteolysis by counteracting endogenous protease inhibitors. Beyond the protein level, proteolytic enzymes are involved in key decisions during development that determine life and death – from single cells to adult individuals. In particular, we are becoming aware of the subtle role that proteases play in signaling events within proteolysis networks, in which the enzymes act synergistically and form alliances in a web-like fashion. Proteases come in different flavors. At least five families of mechanistically distinct enzymes and even more inhibitor families are known to date, many family members are still to be studied in detail. We have learned a lot about the diversity of the about 600 proteases in the human genome and begin to understand their physiological roles in the degradome. However, there are still many open questions regarding their actions in pathophysiology. It is in this area where the development of small molecule inhibitors as therapeutic agents is extremely promising. Approaching proteolysis as the most important, irreversible post-translational protein modification essentially requires an integrated effort of complementary research disciplines. In fact, proteolytic enzymes seem as diverse as the scientists working with these intriguing proteins. This book reflects the efforts of many in this exciting field of research where team and network formations are essential to move ahead.

The amyloid precursor protein APP plays a key role in the pathogenesis of Alzheimer’s disease (AD), as proteolytical cleavage of APP gives rise to the Aβ peptide which is deposited in the brains of Alzheimer patients. Despite this, our knowledge of the normal cell biological and physiological functions of APP and the closely related APLPs is limited. This may have hampered our understanding of AD, since evidence has accumulated that not only the production of the Aβ peptide but also the loss of APP-mediated functions may contribute to AD pathogenesis. Thus, it appears timely and highly relevant to elucidate the functions of the APP gene family from the molecular level to their role in the intact organism, i.e. in the context of nervous system development, synapse formation and adult synapse function, as well as neural homeostasis and aging. Why is our understanding of the APP functions so limited? APP and the APLPs are multifunctional proteins that undergo complex proteolytical processing. They give rise to an almost bewildering array of different fragments that may each subserve specific functions. While Aβ is aggregation prone and neurotoxic, the large secreted ectodomain APPsα - produced in the non-amyloidogenic α-secretase pathway - has been shown to be neurotrophic, neuroprotective and relevant for synaptic plasticity, learning and memory. Recently, novel APP cleavage pathways and enzymes have been discovered that have gained much attention not only with respect to AD but also regarding their role in normal brain physiology. In addition to the various cleavage products, there is also solid evidence that APP family proteins mediate important functions as transmembrane cell surface molecules, most notably in synaptic adhesion and cell surface signaling. Elucidating in more detail the molecular mechanisms underlying these divers functions thus calls for an interdisciplinary approach ranging from the structural level to the analysis in model organisms. Thus, in this research topic of Frontiers we compile reviews and original studies, covering our current knowledge of the physiological functions of this intriguing and medically important protein family.

As the average life expectancy of many populations throughout the world increases, so to does the incidence of such age-related neurodegenerative disorders as Alzheimer's, Parkinson's, and Huntington's diseases. Rapid advances in our understanding of the molecular genetics and environmental factors that either cause or increase risk for age-related neurodegenerative disor ders have been made in the past decade. The ability to evaluate, at the cellular and molecular level, abnormalities in postmortem brain tissue from patients, when taken together with the development of valuable animal and cell-culture models of neurodegenerative disorders has allowed the identification of sequences of events within neurons that result in their demise in specific neurodegenerative disorders. Though the genetic and environmental factors that pro mote neurodegeneration may differ among disorders, shared biochemical cascades that will ultimately lead to the death of neurons have been identified. These cascades involve oxyradical production, aberrant regulation of cellular ion homeostasis and activation of a stereotyped sequence of events involving mitochondrial dysfunction and activa tion of specific proteases. Pathogenesis of Neurodegenerative Disorders provides a timely compilation of articles that encompasses fundamental mechanisms involved in neurodegenerative disorders. In addition, mechanisms that may prevent age-related neurodegenerative disorders are presented. Each chapter is written by an expert in the particular neurodegenerative disorder or mechanism or neuronal death discussed.

This eBook is a collection of articles from a Frontiers Research Topic. Frontiers Research Topics are very popular trademarks of the Frontiers Journals Series: they are collections of at least ten articles, all centered on a particular subject. With their unique mix of varied contributions from Original Research to Review Articles, Frontiers Research Topics unify the most influential researchers, the latest key findings and historical advances in a hot research area! Find out more on how to host your own Frontiers Research Topic or contribute to one as an author by contacting the Frontiers Editorial Office: frontiersin.org/about/contact.