Studies have identified important families of proteins (denoted: heat shock or stress proteins, Hsps) which display an enhanced expression in response to heat shock or other physiological stresses. Besides the characterization of the genes encoding Hsp and the mechanisms of their induction, recent studies have concentrated on the function of these proteins. It was shown that the expression of Hsp protects the cell against different types of aggressions. In addition,Hsp can regulate essential biochemical processes in unstressed cells. For example, members of the Hsp60 and Hsp70 families act as ATP-binding proteins allowing the folding of nascent or denatured proteins as well as the assembly or disassembly of protein complexes. These observations have led to the discovery of the molecular chaperone concept (Ellis and Hemmingsen 1989). Amongst the proteins whose expression is up-regulated by heat shock or other types of stresses are the small stress proteins also denoted (sHsps, sHsp or sHSP). Small stress proteins encompass a large numbers of related proteins which are represented in virtually all organisms, including prokary- otes. These polypeptides share a structural domain, often referred to as the a-crystallin domain, common to the lens protein alpha-crystallin (Ingolia and Craig 1982;Wistow 1985). In addition to being increased in response to several types of stresses, the Hsp level is also upregulated during development and correlates with the differentiation and oncogenic status of the cell. In spite of the fact that sHsp can confer cellular protection against stresses,their molecular function has remained enigmatic for years.

Table of Contents:
Evolution and Diversity of Prokaryotic Small Heat Shock Proteins.- 1 Introduction.- 2 sHsps in Prokaryotes.- 3 Are sHsps Dispensable in Some Pathogenic Bacteria?.- 4 Phylogenetic Analysis of Prokaryotic sHsps.- 5 Lateral Transfer or Convergent Evolution of Prokaryotic sHsp Genes.- 6 Secondary Structure Prediction of the a-Crystallin Domain.- 7 Alignment and Secondary Structure Prediction of the N-Terminal Domain.- 8 Summary and Concluding Remarks.- References.- Discovery of Two Distinct Small Heat Shock Protein (HSP) Families in the Desert Fish Poeciliopsis.- 1 Introduction.- 2 Variation in Small HSPs Among Desert Species of Poeciliopsis.- 3 Variation in Small HSPs Within Poeciliopsis Species.- 4 Discovery of Two Classes of Small HSPs in a Single Taxon.- References.- Chaperone Function of sHsps.- 1 Introduction.- 2 General Aspect of Chaperone function.- 3 The Chaperone Properties of sHsps.- 4 Conclusions.- References.- The Small Heat Shock Proteins of the Nematode Caenorhabditis elegans: Structure, Regulation and Biology.- 1 Introduction.- 2 The Small Heat Shock Protein Family of C. elegans.- 3 The 16-kDa Stress Proteins (Hspl6s).- 4 The 12-kDa Small Heat Shock Proteins (Hspl2s).- 5 SIP-1.- 6 Hspl7.5.- 7 Hsp25.- 8 Hsp43.- 9 Conclusions and Prospects.- References.- Drosophila Small Heat Shock Proteins: Cell and Organelle-Specific Chaperones?.- 1 Introduction.- 2 Members of the Small Heat Shock Proteins Family.- 3 Transcriptional Regulation.- 4 Intracellular Localisation-Analysis of Targeting Signals.- 5 Biochemical Properties and Post-Translational Modifications.- 6 Stress-Induced Expression of sHsp.- 7 Developmental Expression of sHsp.- 8 Conclusion.- References.- The Developmental Expression of Small HSP.- 1 Introduction.- 2 Small HSP in Extraembryonic Development.- 3Small HSP in Ectodermal Lineages.- 4 Small HSP in Mesodermal Lineages.- 5 Small HSP in Endodermal Lineages.- 6 Phosphorylation of sHSP During Development.- 7 Developmental Regulation of Small HSP Gene Expression.- 8 The Role of Small HSP in Development and Differentiation.- 9 Small HSP in the Development of Non-Mammals.- References.- Expression and Phosphorylation of Mammalian Small Heat Shock Proteins.- 1 Introduction.- 2 Modification of the Expression of Hsp27 and ?B-crystallin.- 3 Phosphorylation of Small Hsps.- References.- sHsp-Phosphorylation: Enzymes, Signaling Pathways and Functional Implications.- 1 Introduction.- 2 Identification of Phosphorylated sHsps.- 3 The Major Pathway for sHsp Phosphorylation Via p38 MAPK and MAPKAP Kinase 2.- 4 Other Pathways.- 5 Functional Aspects of sHsps-Phosphorylation.- References.- Small Stress Proteins: Modulation of Intracellular Redox State and Protection Against Oxidative Stress.- 1 Introduction.- 2 Cell Death Induced in Response to Oxidative Stress.- 3 sHsp Expression Protects Against Oxidative Stress-Induced Cell Death.- 4 sHsp Expression Can Also Enhance Oxidative Stress Induced Cell Death.- 5 Conclusions and Future Perspectives.- References.- Small Stress Proteins: Novel Negative Modulators of Apoptosis Induced Independently of Reactive Oxygen Species.- 1 Introduction.- 2 sHsp Expression Protects Against Apoptosis Induced Independently of ROS Formation.- 3 Hsp27 as Essential Anti-Apoptotic Protein During Early Cell Differentiation.- 4 Hsp27 Modulates Apoptosis in Vivo and Enhances the Tumorigenicity of Transformed Cells.- 5 Conclusions and Future Perspectives.- References.- Hsp27 as a Prognostic and Predictive Factor in Cancer.- 1 Introduction.- 2 Female Genital Tract.- 3 Nervous System and Digestive Tract.- 4Hematological Malignancies.- 5 Genitourinary Tract.- 6 Tumors from Others Tissues.- 7 Conclusion.- References.- Cytoskeletal Competence Requires Protein Chaperones.- 1 Symmary.- 2 Human Diseases Caused by sHSF Mutations.- 3 sHSP Interaction with the Cytoskeleton.- 4 Functional Implications of the Interactions.- 5 The Chaperone-Cytoskeleton Complex. The Guardian of the Cytoplasm?.- References.- Hsp27 in the Nervous System: Expression in Pathophysiology and in the Aging Brain.- 1 Introduction.- 2 Constitutive Expression of Hsp27 in the Nervous System.- 3 Expression of Hsp27 in Pathophysiology.- 4 Expression of Hsp27 in Diseases of the Aging Brain.- 5 Conclusions.- References.- Protection of Neuronal and Cardiac Cells by HSP27.- 1 Protective Effect of Heat Shock Proteins.- 2 Protective Effect of HSP27.- 3 Protective Effect of HSP27 in Neuronal and Cardiac Cells.- 4 Conclusion.- References.