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Book Reviews |
edited by C. G. dos Remedios and D. D. Thomas
Springer-Verlag (2001) 269 pages. ISBN 3-540-67110-2
£82.50/US$120.00
Department of Cell and Molecular Pharmacology, University of California, School of Medicine, San Francisco, CA 94143, USA
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Like other established fields, the cytoskeleton has its canon — a collection of books found in every lab studying microtubules, actin or intermediate filaments. First, there is the grand catalog, The Handbook of Cytoskeletal and Motor Proteins by Kreis and Vale. It is a comprehensive and democratic bestiary, devoting nearly as much space to exotic proteins such as transgelin and hisactophilin as to actin itself. For a residue by residue tour of major players such as actin, myosin and spectrin there is the Protein Profiles series. For detailed methods and protocols there is the remarkable Cell Biology: A Laboratory Manual edited by Julio Celis, as well as a handful of volumes of Methods in Enzymology. In addition, at the introductory level there are several good books including Molecules of the Cytoskeleton by Amos and Amos and the recent Mechanics of Motor Proteins and the Cytoskeleton by Jonathan Howard.
Molecular Interactions of Actin is a slim volume that aims for the middle parts of this canon, somewhere between the introductory remarks of Amos and Amos and the wonky detail of Protein Profiles. Recent years have seen a renaissance of interest in actin, particularly in the assembly of actin networks in response to intracellular signals. New investigators enter the field daily and struggle to master a literature built up over more than 35 years. It is now easier than ever for the interested student to perform an impressively uninterpretable experiment on actin filament assembly. Therefore, there is clearly a need for such books — collections of readable and scholarly essays that introduce the general audience to key concepts, molecules and techniques.
The strengths of the book come from the impressive collection of contributors, which includes many longtime actin wonks — people who have made significant contributions to the field. The book's weaknesses arise from the fact that it is essentially the proceedings of a scientific meeting (The Fourth Pentennial Actin Conference, held in Hawaii in 1998). Like all published proceedings, the editorial focus is a bit blurry and the quality of contributions is uneven. However, the best essays in the collection are true gems.
Gems include Fumio Oosawa's historical account of the study of actin assembly. Oosawa helped launch the biochemical study of the non-muscle actin cytoskeleton in the 1960s. Among other achievements he was first to discover and purify actin from a non-muscle source and he was first to describe filament assembly as a nucleation-condensation reaction with a well-defined critical concentration. His brief essay sketches the early intellectual and experimental foundations of our understanding of actin filament structure and assembly and provides a bibliography of important results from the 1940s to the 1970s.
Several other chapters deserve special mention including those describing fluorescence microscopy assays of actin assembly and the study of actin filament structure with FRET, as well as the review of the role of adenosine nucleotides and divalent cations in actin structure.
Four essays stand out above the others and, together, nearly justify the hefty price of this little book. The first is an outstanding review of the pathways by which extracellular signals control the actin cytoskeleton, by Thomas Beck, Pierre-Alain Delley and Michael Hall. Most cell biologists are aware that Rho-family G-proteins somehow regulate actin assembly and organization. Few, however, can say more than that. The authors discuss signaling to the actin cytoskeleton in three well-studied systems: budding yeast, fruit flies and mammals, with each section divided neatly into molecules and pathways. In budding yeast the authors describe shmoo formation in response to mating pheremones, filamentous growth in response to nitrogen starvation, and de- and re-polarization in response to stress. The breadth and careful organization of this chapter (and its gigantic bibliography) ensure that it will be a useful resource for many years to come.
The second is a discussion of actin filament networks by Paul Janmey, Jagesh Shah, Jay Tang and Thomas Stossel. This is a difficult but important subject — where the rubber hits the road. After all the signaling and all the worry over who phosphorylates whom, we still need to understand how a cell converts this information into a 3D polymer network that can do something useful. The authors describe the mechanical properties of actin networks and consider the effects of filament crosslinking, severing and capping proteins on network architecture. They also discuss connections between actin and other cytoskeletal elements such as microtubules and intermediate filaments. And for those so inclined, they include a gentle introduction to mathematical theories of semi-flexible polymers. Personally, I would have liked an additional chapter of similar depth describing recent work on the mechanical properties of individual actin filaments and on theories of how free energy of polymerization is converted into cellular movements.
Third, Lisa Belmont and David Drubin provide a compact but remarkably comprehensive guide to yeast actin mutants. Prokaryotic chaperones cannot fold actin and so S. cerevisiae has been the most important organism for generating actin mutants for genetic and cell biological studies as well as biochemical analysis. Belmont and Drubin explain the contributions of yeast mutants to our understanding of many areas of actin biochemistry, including filament structure and dynamics, nucleotide binding and hydrolysis, and the interaction of both small molecules and proteins with actin monomers and filaments. The centerpiece of the essay is a massive table of all published point mutants in the budding yeast actin gene (there are 90) together with their in vivo phenotypes and, when known, their effects on actin biochemistry. Smart money says this table will be the most-often-photocopied four pages of the book.
Finally, perhaps the most outstanding contribution is a review of the ADF/cofilin proteins by Amy McGough, Brian Pope and Alan Weeds. It is quite simply the best review of the subject that I have read. Now, when students or colleagues ask me a question about cofilin, or when they ask my advice on how to write a concise and informative review, I point them to this chapter. My greatest frustration with the book is that I wish it contained reviews of similar scope and quality on profilin and capping protein (two other ubiquitous and widely misunderstood regulators of actin dynamics). With these additions the book would provide all the information needed for a newcomer to tackle the most current literature. As it stands, the book is still useful and should find its way onto the shelf of every well-read actin wonk.
Footnotes
* Collins defines a `wonk' as a person who is obsessively interested in a
specified subject. 
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