Séminaire IBIP
Les séminaires ont lieu sur le Campus Montpellier SupAgro/INRA de La Gaillarde (2, place P. Viala Montpellier)

Jeudi 30 janvier 2014
Amphi 208 (Cœur d’Ecole) à 14h

On calcium, heat sensing and heat shock survival

Andrija Finka
Department of Plant Molecular Biology, University of Lausanne, Switzerland

Sessile organisms such as plants experience daily heat-shocks, with temperature variations rising up to 30°C between 2 am and 2 pm. Diurnal temperature variations may be particularly extreme for organisms that evolved far from large temperate water bodies, such as oceans, and populated intemperate inland habitats exposed to abrupt environmental stresses, such as freezing, heating, excess light, excess oxygen radicals and to more gradual seasonal stresses, such as dehydration, nutriment starvation and salt stress. To cope with a noxious heat shock, exposed organisms need to timely develop appropriate molecular defences that can prevent and repair heat damages, mostly in labile lipids and proteins. A mild rise of ambient temperature transiently increases the fluidity of the plasma membrane, which in turn, activates the transient opening and depolarisation of specific heat-sensitive Ca2+ channels (Saidi et al. 2009). Members of the cyclic nucleotide gates channels (CNGCs) were recently identified as being the primary heat-sensors of land plants (Finka et al. 2012; Finka and Goloubinoff 2013). Depending on the rate of temperature increase, the duration and intensity of the heat priming preconditions, terrestrial plants may thus acquire an array of heat shock protein-based thermotolerance mechanisms against upcoming, otherwise lethal, extreme heat waves. Currently we are extending our search on physiologically heat-shocked human cultured cells. We have recently shown that in unstressed cells, the members of the chaperome network contributed to about 10% of the total protein mass approximately (Finka and Goloubinoff 2013). Quantitative high-throughput proteomics of human cells allowed us to establish the amount of proteins in an unchallenged state at 37°C and during a heat shock at 41°C. We found that only few HSPs are massively synthesized in terms of mass and copy numbers during a heat shock, whereas many proteins are slightly degraded in across-the-board manner. Thus, heat accumulated HSPA8 and HSPA1A, representing cognate and inducible isoform of cytosolic Hsp70, differ more than two orders of magnitude, which, together with individual mRNA assessment, revolve the view of the fold change and strongly argues for the absolute values in individual protein and mRNA analysis. By correlating the protein and mRNA synthesis rates we show translatability rate of analyzed HSPs, which is the similar for HSPA1A and HSPA8 implying their need-to-use basis in apoptosis and protein synthesis, respectively.

Finka A, Goloubinoff P (2013) Proteomic data from human cell cultures refine mechanisms of chaperone-mediated protein homeostasis. Cell Stress and Chaperones:1-15. doi:10.1007/s12192-013-0413-3

Finka A, Cuendet AFH, Maathuis FJM, Saidi Y, Goloubinoff P (2012) Plasma Membrane Cyclic Nucleotide Gated Calcium Channels Control Land Plant Thermal Sensing and Acquired Thermotolerance. Plant Cell 24 (8):3333-3348. doi:DOI 10.1105/tpc.112.095844

Finka A, Goloubinoff P (2013) The CNGCb and CNGCd genes from Physcomitrella patens moss encode for thermosensory calcium channels responding to fluidity changes in the plasma membrane. Cell Stress and Chaperones:1-8. doi:10.1007/s12192-013-0436-9

Saidi Y, Finka A, Muriset M, Bromberg Z, Weiss YG, Maathuis FJM, Goloubinoff P (2009) The Heat Shock Response in Moss Plants Is Regulated by Specific Calcium-Permeable Channels in the Plasma Membrane. Plant Cell 21 (9):2829-2843. doi:DOI 10.1105/tpc.108.065318

Contact : Sabine Zimmermann

Contacts IBIP :
Sabine Zimmermann
Philippe Nacry
Christine Granier
Chantal Baracco