Advances in Molecular and Cell Biology Series

There has been an enormous advance in our understanding of the regulation of the cell division cycle in the last five years. The leap in understanding has centered on the cell cycle control protein p34cdc2 and its congeners and on the cyclins. The most important insight to emerge has been that cell cycle control mechanisms and their participating proteins are very well-conserved through evolution. This has created a spectacular growth in knowledge as data from one organism have been readily applied to another. In this volume, there are sea urchin and frog eggs, as well as mammalian cells and yeast. There is also an illustration of how fruitful the genetic approach can be in other organisms than yeast with a chapter on Aspergillus nidulans. The cell cycle kinase has been well-characterized and has also been well-exposed in numerous proceedings volumes and collections. In this issue of Advances in Molecular Cell Biology, the cell cycle kinase is ever present, but in the early chapters it has a supporting role. Center stage are the regulatory mechanisms that control the kinase. The contribution that the centrosome (the organelle of cell division) makes to cell cycle regulation are described. The part played by calcium and calcium-controlled regulatory proteins is emphasized. The importance of phosphatase as well as kinase activity to cell cycle regulation is stressed. The last words are reserved for the mitotic kinase: the last chapters describe its effects and its regulation in cell-free systems.

One prerequisite for the evolution of multicellular organisms was the invention of mechanisms by which cells could adhere to one another. At some point in our history, dividing cells no longer went their separate protozoic ways in the primordial oceans, but instead found that by maintaining an association, by sticking together but not fusing, numerous evolutionary advantages became possible. The subsequent development of specialized tissues and organs depended on the elaboration of incredibly sophisticated, regulatable cell-to-cell adhesion mechanisms which are known to operate in biological processes as diverse as the growth of the embryo, the immune response, the establishment of connections between nerve cells, and arteriosclerosis, to name just a few. Although we can only guess at the ancestral mechanisms that fostered the first primitive intercellular unions, some one billion years ago, we now recognize contemporary molecular "themes" with presumably ancient origins that mediate cell-cell interactions. The chapters in this book serve as useful, thought-provoking, but not exhaustive, commentaries on contemporary topics within the broad field of cell adhesion. If the reader detects a slight tilt toward those adhesion molecules that function in the nervous system, this is merely a reflection of this editor's interests, biases, and of course, limitations.

In December 1992, the Department of Pure and Applied Biochemistry at the Chemical Center in Lund, Sweden, organized an international meeting, the Mosbach Symposium on Biochemical Technology, to celebrate the 60th birthday of professor Klaus Mosbach, one of the founders of modern biotechnology. The history of Pure and Applied Biochemistry had its start in 1970, a couple of years after the foundation of the Chemical Center. Klaus Mosbach has been its professor and head of Pure and Applied Biochemistry since its start. During the 1980's he also maintained a professorship at the ETH in Zürich, Switzerland. Professor Mosbach is internationally well-known and he has world-leading position within the field of immobilization of bioactive substances and cells as well as affinity chromatography. In 1990, Professor Mosbach was awarded the gold medal by the Royal Swedish Academy of Engineering Sciences for his contributions to biotechnology, especially on the immobilization of bioactive substances. The research activities of the Department of Pure and Applied Biochemistry cover a broad area, such as affinity and separation techniques, bioprocess control, biosensors, development of new carriers and new immobilization procedures for small molecules as well as proteins and cells, including animal and plant cells, gene technology, processes based on immobilized biocatalysts, and construction of organic polymers with enzyme-like properties. The hallmark of the department is its diversified research that generates considerable synergistic effects that are manifested by many new techniques and concepts emanating from the laboratory during the last 20 years. Several of these are marketed by various biotechnology companies. At this meeting we therefore arranged for some of the world's leading experts in biochemistry and biotechnology to give lectures. The topics covered comprise enzyme technology, immobilization of enzymes and cells, abzymes, metabolic engineering, biosensors, and molecular recognition. The official gift from the symposium committee and the participants is this "Festschrift" which covers several important fields of research within the area of biochemical technology. We have made a very unusual approach and have let the "hero of the occasion" present the history of his research.

A large number of newly-synthesized polypeptides must cross one or several intracellular membranes to reach their functional locations in the eukaryotic cell. The mechanisms of protein trafficking, in particular the post-translational targeting and membrane translocation of proteins, are of fundamental biological importance and are the focus of intensive research world-wide. For more than 15 years, mitochondria have served as the paradigm organelle system to study these processes. Although key questions, such as how precisely proteins cross a membrane, still remain to be answered, exciting progress has been made in understanding the basic pathways of protein import into mitochondria and the components involved. In addition to a fascinating richness and complexity in detail, the analysis of mitochondrial protein import has revealed mechanistic principles of general significance: Major discoveries include the demonstration of the requirement of an unfolded state for translocation and of the essential role of molecular chaperones on both sides of the membranes in maintaining a translocation-competent conformation and in protein folding after import. It is becoming clear how a polypeptide chain is "reeled" across the membrane in an ATP-dependent process by the functional cooperation of membrane proteins, presumably constituting part of a transmembrane channel, with peripheral components at the trans-side of the membrane. In this volume, eminent experts in the field take the time to review the central aspects of mitochondrial biogenesis. The logical order of the 16 chapters is determined by the sequence of steps during protein import, starting with the events taking place in the cytosol, followed by the recognition of targeting signals, the translocation of precursor proteins across the outer and inner membranes, their proteolytic processing and intramitochondrial sorting, and finally their folding and oligomeric assembly. In addition, the mechanisms involved in the export of mitochondrially encoded proteins as well as recent advances in understanding the division and inheritance of mitochondria will be discussed.

Notwithstanding widespread studies and even several biological journals devoted to temperature, it is difficult to perceive a field of thermobiology as such. Interest in the effects of temperature of biological systems is fragmented into specific thermal ranges and often connected with particular applications: subzero cryobiology and preservation of cells and tissues or survival of poikilotherms, para-zero cryobiology and preservation of whole organs and survival of whole animals, intermediate ranges and physiological adaption and regulation, high temperatures and use of heat for killing cancer cells, very high temperatures and limits of biological structure. Yet it has not always been so, and there are good reasons why it need not remain so. General and comparative physiologists such as W.J. Crozier, H. Precht, J. Belehradek, F. Johnson, C.L. Prosser, and others have sought throughout this century to lay foundations for unified approaches to temperature in biological systems. Recent findings also serve to suggest principles and processes that span the range of temperatures of biological interest. Microviscosity of membranes is an issue originally of interest to low temperature biologists but with relevance to limiting high temperatures; conversely for protein structure. Certain "heat shock proteins" now appear to be responses to generalized stress, including low temperature. Inevitably, the chapters of this book reflect the "zonal" character of thermobiology: two chapters (by Storey and Raymond) deal with protection against subfreezing temperatures; three (Hazel, membrane structure, Dietrich, microtubular structure, and Kruuv, cell growth) deal with the effects of and modulation to cool-to-moderate superfreezing temperatures, one (Willis) with modulation (of membrane ion transport) to moderate-to-high temperatures and two (Li, heat shock proteins and Lepock, proteins in general) with stressfully high temperatures. Explicit in each of these chapters, however, are principles and issues that transcend the parochialism of the temperature range under consideration.

Recent advances in protein structural biology, coupled with new developments in human genetics, have opened the door to understanding the molecular basis of many metabolic, physiological, and developmental processes in human biology. Medical pathologies, and their chemical therapies, are increasingly being described at the molecular level. For single-gene diseases, and some multi-gene conditions, identification of highly correlated genes immediately leads to identification of covalent structures of the actual chemical agents of the disease, namely the protein gene products. Once the primary sequence of a protein is ascertained, structural biologists work to determine its three-dimensional, biologically active structure, or to predict its probable fold and/or function by comparison to the data base of known protein structures. Similarly, three-dimensional structures of proteins produced by microbiological pathogens are the subject of intense study, for example, the proteins necessary for maturation of the human HIV virus. Once the three-dimensional structure of a protein is known or predicted, its function, as well as potential binding sites for drugs that inhibit its function, become tractable questions. The medical ramifications of the burgeoning results of protein structural biology, from gene replacement therapy to "rational" drug design, are well recognized by researchers in biomedical areas, and by a significant proportion of the general population. The purpose of this book is to introduce biomedical scientists to important areas of protein structural biology, and to provide an insightful orientation to the primary literature that shapes the field in each subject. The chapters in this volume cover aspects of protein structural biology which have led to the recognition of fundamental relationships between protein structure and function.

Both eukaryotic and prokaryotic cells depend strongly on the function of ion pumps present in their membranes. The term ion pump, synonymous with active ion-transport system, refers to a membrane-associated protein that translocates ions uphill against an electrochemical potential gradient. Primary ion pumps utilize energy derived from chemical reactions or from the absorption of light, while secondary ion pumps derive the energy for uphill movement of one ionic species from the downhill movement of another species. In the present volume, various aspects of ion pump structure, mechanism, and regulation are treated using mostly the ion-transporting ATPases as examples. One chapter has been devoted to a secondary ion pump, the Na+-Ca2+ exchanger, not only because of the vital role played by this transport system in regulation of cardiac contractility, but also because it exemplifies the interesting mechanistic and structural similarities between primary and secondary pumps.

Few cells conform to the stereotype of the spherical blob hastily scribbled on chalkboards and, regrettably, sometimes even displayed prominently in textbooks. Instead, real cells display a remarkable degree of structural and functional asymmetry. In modern cell biological parlance, this asymmetry has come to be lumped under the general heading of "cell polarity". Cell polarity is by no means restricted to the cells of tissues and organs, but can also be displayed by cells that lead a more solitary existence. The amazing extent to which cell morphology is correlated with function has long been a source of inspiration for biologists. Today the fascination continues unabated in the field of cell polarity, where it is fueled by an ever-deepening appreciation for the ways that fundamental cellular processes, such as membrane trafficking and cytoskeleton assembly, contribute to the establishment and maintenance of cell polarity. In the ensuing chapters, a collection of experts will summarize and interpret the findings obtained from basic research on cell polarity in a diverse array of experimental systems.

The rapid expansion of the area of free radical biology in the last 25 years has occurred within a framework of assumptions and preconceived notions that has at times directed the course of this movement. The most dominant of these notions has been the view that free radical production is without exception a bad thing, and that the more efficient our elimination of these toxic substances, the better off we will be. The very important observation by Bernard Babior and colleagues in 1973 that activated phagocytes produce superoxide in order to kill micro organisms, served to illustrate that constructive roles are possible for free radicals. For many in the field, however, this merely underscored the deadly nature of oxygen-derived radicals, both from the microbe's point of view and from the host's as well. (Phagocyte-produced superoxide is responsible in part for the tissue injury manifested as inflammation. See Harris and Granger, Chapter 5, and Leff, Hybertson and Repine, Chapter 6.) Mother Nature, however, has a penchant for being able to make a silk purse from a sow's ear. If one is dealt a bad hand, one must simply make the best of it. After two decades of focusing on the destructive side of free radicals, the last few years have begun to reveal a new and finer perspective on free radical metabolism - a role in regulation of cellular function (see Schulze-Osthoff and Baeuerle, Chapter 2). Evidence from a number of sources suggests that an increase in the oxidative status of cell encourages that cell to grow and divide. Increasing the expression of mangnese superoxide dismutase can suppress the malignant phenotype of melanon cells (see Oberley and Oberley, Chapter 3). Oxidative stress beyond a certain poitosis (from the Greek, literally "to fall apart"). Is this suicide response an evolutionary fail-safe device to curtail tumorogenesis? Does oxidative stress-induced apoptosis account for the loss of immune cells in AIDS (see Flores and McCor Chapter 4)? This volume attempts to present the spectrum of roles, both good and bad played by active oxygen species as understood at this point in the evolution of this field of free radical biology.

The aim of "The Adhesive Interaction of Cells" has been to assemble a series of reviews by leading international experts embracing many of the most important recent developments in this rapidly expanding field. The purpose of all biological research is to understand the form and function of living organisms and, by comprehending the normal, to find explanations and remedies for the abnormal and for disease conditions. The molecules involved in cell adhesion are of fundamental importance to the structure and function of all multicellular organisms. In this book, the contributors focus on the systems of vertebrates, especially mammals, since these are most relevant to human disease. It would have been equally possible to concentrate on developmental processes and adhesion in lower organisms. A major function of adhesion molecules is to bind cells to each other or to the extracellular matrix, but they are much more than "glue". Adhesions in animal tissues must be dynamic-forming, persisting, or declining in regulated fashion- to facilitate the mobility and turnover of tissue cells. Moreover, the majority of adhesion molecules are transmembrane molecules and thus provide links between the cells and their surroundings. This gives rise to another major function of adhesion molecules, the capacity to transduce signals across the hydrophobic barrier imposed by the plasma membrane. Such signal transduction is crucially important to many aspects of cellular function including the regulation of cell motility, gene expression, and differentiation. The work in this book progresses through four sections. Part I discusses the four major families of adhesion molecules themselves, the integrins (Green and Humphries), the cadherins (Stappert and Kemler), the selectins (Tedder et al.) and the immunoglobulin superfamily (Simmons); part 2 considers junctional complexes involved in cell interactions: focal adhesions and adherens junctions (Ben Ze'ev), desmosomes (Garrod et al.), and tight junctions (Citi and Cordenonsi). The signaling role of adhesion molecules is the focus of part 3, through integrins and the extracellular matrix (Edwards and Streuli), through platelet adhesion (Du and Ginsberg), and in the nervous system (Hemperley). In part 4, the aim is to show how adhesive phenomena contribute to important aspects of cell behavior and human health. Leukocyte trafficking (Haskard et al.), cancer metastasis (Marshall and Hart), cell migration (Paleck et al.), and implantation and placentation (Damsky et al.) are the topics considered in depth. The different sections are, of course, not mutually exclusive: it is both undesirable and impossible to separate structure from function when considering cell adhesion. Each chapter has its unique features, but some overlap is both invevitable and valuable since it provides different perspectives on closely related topics. We hope that the whole contributes a valuable and stimulating consideration of this important topic.

As a result of the key advances made more than 30 years ago, specifically the ability to isolate islets of Langerhans from the pancreas, the ability to measure insulin accurately by immunoasay, and the development of microchemical techniques for studying cells and their components, many research volumes, symposium reports, and original papers have been produced. This explosion of interest has probably had at least three stimuli: 1. the inherent scientific interest in understanding secretion of the pancreatic ß-cell 2. the ß-cells relevance to a very common disease 3. the availability of funding from specific sources related to diabetes research, for instance, Juvenile Diabetes Foundation International and the British Diabetic Association. As a result of all this activity, detailed scientific literature including research reviews are readily available. Surprisingly enough, there are relatively few attempts to summarize this great bulk of knowledge in a way that is accessible to the newcomer to this field and this book is intended to bridge this gap.