Doctoral school - recruitment

Adaptation to environmental stress is essential for survival of land snails since drastic changes such as cold, heat, and osmotic shocks are lethal for them. During heat/cold shock, the cell membrane fluidity, enzymatic activity and other physiological processes are changed. Heat shock proteins (HSPs) protect organism from detrimental effects of heat and oxidative stress while the crucial role in cold adaptation play cold shock proteins (CSPs). Despite of the fact that the adaptation to changes in environmental conditions is extensively investigated in different species of animals, the role of heat and specially cold shock proteins in land snails have not been fully studied yet.

Hypothesis: the snails occupying extreme environments should employ a "preparative defence" strategy involving maintenance of high constitutive levels of HSP/CSP in their cells as a mechanism for protection against periods of extreme and unpredictable stress. Knowledge about the role of HSPs in snails in still poor, therefore it is interesting whether the stress tolerance depends on the synthesis of HSPs. I assume that their upregulation may enhance survival under stress conditions by rescuing critical proteins and reducing the energetic cost associated with protein damage. Given that winter temperature for snails vary from above 0 to -20C or less, the constitutive chaperone defenses could also be necessary to stabilize protein conformation over wide ranges of environmental temperatures, as well as during freeze/thaw cycles. Identification of CSPs in snails will be one of the main objectives of the project. CSPs have a highly conserved (from bacteria to higher plants and animals) nucleic acid binding domain, called the cold shock domain. In plants they play essential roles in acquiring freezing tolerance. Taking into consideration that there are no data concerning the proteins involvement in freeze tolerance or freeze avoidance of animals, I would like to determine expression of the proteins during exposure to freezing in snails. It should be stressed that direct relation of CSPs level with functionality of these protein during feeze/thaw cycles was not investigated so far.

The experiments will be performed on snails exposed to different temperatures and humidities under controlled laboratory conditions, and concentration of HSPs and CSPs will be measured during the seasonal hypometabolism/activity cycles. Western blot analysis will be used to detect HSPs and CSPs, but quantitatively HSPs and CSPs will be analyzed by ELISA. Moreover, immunoprecipitation experiments should allows to identify proteins that interact with HSPs and CSPs.

At the beginning we will check if CSPs are present in the snails’ cells. It is known that some of them are multifunctional proteins involved in the regulation of transcription and translation, drug resistance, cell proliferation and one of them was identified as an essential regulator of larval development in C. elegans and still others play a role in reprogramming human somatic cells into pluripotent stem cells or participate in differentiation of muscular tissue. However, there is still no clear answer about the physiological role of the proteins in land snails. The project is the first attempt to combine interdisciplinary methods of physiology and molecular biology to determine the adaptation of snails to environmental stress (especially cold shock/freezing).

It is expected that HSP/CSP expression determines dehydration tolerance in the natural annual cycles of activity/hypometabolism such as activity/estivation (during summer) and activity/overwintering (in winter), resceptively.