Cells from virtually all organisms respond to a variety of stresses by the rapid synthesis of a highly conserved set of polypeptides termed heat shock proteins (HSPs). The precise functions of HSPs are unknown, but there is considerable evidence that these stress proteins are essential for survival at both normal and elevated temperatures. HSPs also appear to play a critical role in the development of thermotolerance and protection from cellular damage associated with stresses such as ischemia, cytokines, and energy depletion. These observations suggest that HSPs play an important role in both normal cellular homeostasis and the stress response. This mini-review examines recent evidence and hypotheses suggesting that the HSPs may be important modifying factors in cellular responses to a variety of physiologically relevant conditions such as hyperthermia, exercise, oxidative stress, metabolic challenge, and aging.

https://www.physiology.org/doi/pdf/10.1152/japplphysiol.01267.2001

Invited Review: Heat shock proteins: modifying factors in physiological stress responses and acquired thermotolerance

Heat shock proteins.

THE MITOCHONDRIAL GENETIC SYSTEM ....•••••• ••••••••••.• ••••••••••..•......... 291 Organization and Expression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... . . . . . . . . . . 291 Genetic Content 296 Regulation of Mitochondrial Gene Expression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300

Biogenesis of Mitochondria

The cellular stress response is a universal mechanism of extraordinary physiological/pathophysiological significance. It represents a defense reaction of cells to damage that environmental forces inflict on macromolecules. Many aspects of the cellular stress response are not stressor specific because cells monitor stress based on macromolecular damage without regard to the type of stress that causes such damage. Cellular mechanisms activated by DNA damage and protein damage are interconnected and share common elements. Other cellular responses directed at re-establishing homeostasis are stressor specific and often activated in parallel to the cellular stress response. All organisms have stress proteins, and universally conserved stress proteins can be regarded as the minimal stress proteome. Functional analysis of the minimal stress proteome yields information about key aspects of the cellular stress response, including physiological mechanisms of sensing membrane lipid, protein, and DNA damage; redox sensing and regulation; cell cycle control; macromolecular stabilization/repair; and control of energy metabolism. In addition, cells can quantify stress and activate a death program (apoptosis) when tolerance limits are exceeded.

Molecular and evolutionary basis of the cellular stress response

Most heat shock proteins (Hsp) function as molecular chaperones that help organisms to cope with stress of both an internal and external nature. Here, we review the recent evidence of the relationship between stress resistance and inducible Hsp expression, including a characterization of factors that induce the heat shock response and a discussion of the associated costs. We report on studies of stress resistance including mild stress, effects of high larval densities, inbreeding and age on Hsp expression, as well as on natural variation in the expression of Hsps. The relationship between Hsps and life history traits is discussed with special emphasis on the ecological and evolutionary relevance of Hsps. It is known that up-regulation of the Hsps is a common cellular response to increased levels of non-native proteins that facilitates correct protein folding/refolding or degradation of non-functional proteins. However, we also suggest that the expression level of Hsp in each species and population is a balance between benefits and costs, i.e. a negative impact on growth, development rate and fertility as a result of overexpression of Hsps. To date, investigations have focused primarily on the Hsp70 family. There is evidence that representatives of this Hsp family and other molecular chaperones play significant roles in relation to stress resistance. Future studies including genomic and proteonomic analyses will increase our understanding of molecular chaperones in stress research.

https://onlinelibrary.wiley.com/doi/pdf/10.1046/j.1461-0248.2003.00528.x

The evolutionary and ecological role of heat shock proteins

Protein synthesis in salivary glands of Drosophila melanogaster: relation to chromosome puffs.

It was reported recently that the characteristics of a slow-growing strain, called poky, are inherited maternally.(1) This observation has focused attention on strains which grow slowly on complete medium and which have long been known to appear very frequently in material examined in order to detect nutritional mutants of Neurospora. An indication of the frequency of their appearance can be obtained from some figures taken from the data of Beadle and Tatum.(2) Among 8795 ascospores isolated from irradiated material during their study by one of the present authors (M.B.M.), 7049 germinated. Of these, 54 gave rise to strains having easily diagnosed requirements for components present in the complete medium used and, therefore, represented the class of nutritional mutants sought. A much greater number, 489, were distinguishable from wild type because of their slower growth on complete medium. Of these 159 did not grow sufficiently to allow their being tested. The remaining 330 were discarded, either because they grew too rapidly on minimal medium, or because they did not give a well-defined response to the growth-factor mixtures present in the complete medium. Similar figures have been reported by Lein, Mitchell, and Houlahan(3) in a description of a variation in the method of
Beadle and Tatum.(2)

http://www.pnas.org/content/39/7/606.full.pdf

Mendelian and Non-Mendelian Factors Affecting the Cytochrome System in Neurospora Crassa.

https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1155&context=agronomyfacpub

Cytochromes and the succinic acid oxidase system of poky strains of Neurospora.

https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1156&context=agronomyfacpub

Alfred Tissieres

Papers

Protein synthesis in salivary glands of Drosophila melanogaster: relation to chromosome puffs.

Mendelian and Non-Mendelian Factors Affecting the Cytochrome System in Neurospora Crassa.

Cytochromes and the succinic acid oxidase system of poky strains of Neurospora.

Studies on the respiratory system of the poky strain of Neurospora.

Cytochromes and respiratory activities in some slow growing strains of Neurospora.