SURVIVAL UNDER STRESS - MOLECULAR MECHANISMS OF METABOLIC-RATE DEPRESSION IN ANIMALS

For many species, survival under harsh environmental conditions includ es metabolic rate depression, an escape into a hypometabolic or dorman t state. Studies in my laboratory are analysing the molecular mechanis ms and regulatory events that underlie transitions to and from hypomet abolic states in systems including anoxia-tolerant turtles and mollusc s, estivating snails and toads, hibernating small mammals, and freeze tolerant frogs and insects. Our newest research targets two areas: the role of protein kinases in regulating metabolic adjustments and the r ole of stress-induced gene expression in producing specific adaptive p roteins. Protein kinases A, C and G are all linked to stress-induced s ignal transduction in various systems, and new studies also show tissu e-specific activation of mitogen-activated protein kinases (ERK, JNK, see list of abbreviations p38). Protein adaptations supporting stress tolerance are being sought using cDNA library screening, differential display PCR and Northern blotting to analyse gene expression. These te chniques offer new insights into the types of cellular targets that mu st be coordinated to achieve metabolic suppression and facilitate easy analysis of organ-, time-, and stress-specific gene expression. For e xample, freeze-induced gene expression in frog liver includes upregula tion of genes for subunits of fibrinogen and ADP/ATP translocase, wher eas mitochondrial genes coding for subunits of NADH-ubiquinone oxidore ductase subunit 5 and cytochrome C oxidase subunit 1 were upregulated during anoxia in turtle heart.