Cold Shock Response and Adaptation Chapter Abstracts

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Department of Biochemistry, Robert Wood Johnson Medical School, 675 Hoes Lane, Piscataway, New Jersey 08854-5635, USA

The most common stress that living organisms constantly confront in nature is likely to result from temperature changes. Figure 1 shows the temperature changes in Newark, New Jersey during a one year period. The graph shows both average highest and lowest temperatures of each month as indicated by open and solid circles, respectively. One can see that per month there is a difference of approximately 10°C between the highest and the lowest temperatures and annually the temperatures fluctuate from ­5 to 30°C. How do organisms living in this area respond and adapt to the wide temperature changes, in particular, the low-temperature stress or the cold shock? It is interesting to note that these organisms are not exposed to high-temperature stress (heat shock). Nevertheless, while heat-shock effects have been extensively studied in both prokaryotes and eukaryotes, few studies have been carried out to show how living organisms respond to cold shock.

Chapter 2. Cold Shock Response in Escherichia coli
Kunitoshi Yamanaka

Department of Biochemistry, Robert Wood Johnson Medical School, 675 Hoes Lane, Piscataway, NJ 08854, USA

Sensing a sudden change of the growth temperature, all living organisms produce heat shock proteins or cold shock proteins to adapt to a given temperature. In a heat shock response, the heat shock sigma factor plays a major role in the induction of heat shock proteins including molecular chaperones and proteases, which are well-conserved from bacteria to human. In contrast, no such a sigma factor has been identified for the cold shock response. Instead, RNAs and RNA-binding proteins play a major role in cold shock response. This review describes what happens in the cell upon cold shock, how E. coli responds to cold shock, how the expression of cold shock proteins is regulated, and what their functions are.

Chapter 3. Cold Shock Response in Bacillus subtilis
Peter L. Graumann,¹ and Mohamed A. Marahiel²

¹Biological Laboratories, Harvard University, Cambridge, MA 02138, USA
²Biochemie, Fachbereich Chemie, Hans-Meerwein-Straße, Philipps-Universität Marburg, 35032 Marburg, Germany

Following a rapid decrease in temperature, the physiology of Bacillus subtilis cells changes profoundly. Cold shock adaptation has been monitored at the level of membrane composition, adjustment in DNA topology, and change in cytosolic protein synthesis/composition. Some major players in these processes (cold-stress induced proteins and cold acclimatization proteins, CIPs and CAPs) have been identified and mechanisms in cold shock acclimatization begin to emerge; however, important questions regarding their cellular function still need to be answered.

Chapter 4. Cold Shock Response and Low Temperature Adaptation in Psychrotrophic Bacteria
Michel Hébraud¹, and Patrick Potier²

¹Unité de Recherches sur la Viande, Equipe Microbiologie, Institut National de la Recherche Agronomique de Theix, 63122 Saint-Genès Champanelle, France
²Laboratoire d'Ecologie Microbienne, Unité Mixte de Recherche du CNRS 5557, Université Claude Bernard, Lyon I, 69622 Villeurbanne Cedex, France

Psychrotrophic bacteria are capable of developing over a wide temperature range and they can grow at temperatures close to or below freezing. This ability requires specific adaptative strategies in order to maintain membrane fluidity, the continuance of their metabolic activities, and protein synthesis at low temperature. A cold-shock response has been described in several psychrotrophic bacteria, which is somewhat different from that in mesophilic micro-organisms: (i) the synthesis of housekeeping proteins is not repressed following temperature downshift and they are similarly expressed at optimal and low temperatures (ii) cold-shock proteins or Csps are synthesized, the number of which increases with the severity of the shock (iii) a second group of cold-induced proteins, i.e. the cold acclimation proteins or Caps, comparable with Csps are continuously synthesized during prolonged growth at low temperature. Homologues to CspA, the major cold-shock protein in E. coli, have been described in various psychrotrophs, but unlike their mesophilic counterparts, they belong to the group of Caps. Although they have been poorly studied, Caps are of particular importance since they differentiate psychrotrophs from mesophiles, and they are probably one of the key determinant that allow life at very low temperature.

Chapter 5. Responses to Cold Shock in Cyanobacteria
Dmitry A. Los^1,2, and Norio Murata¹

¹National Institute for Basic Biology, Okazaki, Japan
²Institute of Plant Physiology, Russian Academy of Sciences, Moscow, Russia

Acclimation of cyanobacteria to low temperatures involves induction of the expression of several families of genes. Fatty acid desaturases are responsible for maintaining the appropriate fluidity of membranes under stress conditions. RNA-binding proteins, which presumably act analogously to members of the bacterial Csp family of RNA chaperones, are involved in the maintenance of the translation under cold stress. The RNA helicase, whose expression is induced specifically by cold, might be responsible for modifying inappropriate secondary structures of RNAs induced by cold. The cold-inducible family of Clp proteins appears to be involved in the proper folding and processing of proteins. Although genes for cold-inducible proteins in cyanobacteria are heterogeneous, some common features of their untranslated regulatory regions suggest the existence of a common factor(s) that might participate in regulation of the expression of these genes under cold-stress conditions. Studies of the patterns of expression of cold-inducible genes in cyanobacteria have revealed the presence of a cold-sensing mechanism that is associated with their membrane lipids. Available information about cold-shock responses in cyanobacteria and molecular mechanisms of cold acclimation are reviewed in this article.

Chapter 6. Molecular Responses of Plants to Cold Shock and Cold Acclimation
Charles Guy

Plant Molecular and Cellular Biology Program, Department of Environmental Horticulture, University of Florida, Gainesville, Florida 32611-0670, USA

The Plant Kingdom encompasses a grouping of mostly sessile organisms that show extreme variation in morphology, size, ecological adaptation, life cycle, and climatic tolerance. With the exception of low elevation tropical environments, plants living just about anywhere else in the world may be subject to temperatures below that which are optimal for growth and survival. Consequently, the range of tolerance to low temperature stress in the Plant Kingdom is as great as the natural variation in low temperatures. For mesophilic plants, sub-optimal low temperature could range from 15°C down to -55°C. In the past 10 years, more than 100 genes have been shown to be preferentially expressed in response to low temperatures. Significant progress in understanding the responses of plants to low temperature has occurred in the areas of signal perception and transduction pathways, transcriptional control and the characterization of a variety of stress-related proteins. A common aim of much of the research on cold stress in plants is to find ways to enhance the stress tolerance and reduce economic losses.

Chapter 7. Cold Shock Response in Mammalian Cells
Jun Fujita

Department of Clinical Molecular Biology, Faculty of Medicine, Kyoto University, Kyoto, Japan

Compared to bacteria and plants, the cold shock response has attracted little attention in mammals except in some areas such as adaptive thermogenesis, cold tolerance, storage of cells and organs, and recently, treatment of brain damage and protein production. At the cellular level, some responses of mammalian cells are similar to microorganisms; cold stress changes the lipid composition of cellular membranes, and suppresses the rate of protein synthesis and cell proliferation. Although previous studies have mostly dealt with temperatures below 20°C, mild hypothermia (32°C) can change the cell's response to subsequent stresses as exemplified by APG-1, a member of the HSP110 family. Furthermore, 32°C induces expression of CIRP (cold-inducible RNA-binding protein), the first cold shock protein identified in mammalian cells, without recovery at 37°C. Remniscent of HSP, CIRP is also expressed at 37°C and developmentary regulated, possibly working as an RNA chaperone. Mammalian cells are metabolically active at 32°C, and cells may survive and respond to stresses with different strategies from those at 37°C. Cellular and molecular biology of mammalian cells at 32°C is a new area expected to have considerable implications for medical sciences and possibly biotechnology.

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