Book of Abstracts - Australian Centre for Economic Research on ...

3rd Cell Stress Society International Congress on
Stress Responses in Biology and Medicine and
2nd World Conference <strong>of</strong> Stress
technique demonstrated the 24mer to be anomalously abundant, consistent with previous reports which have
culminated in a 3D structure <strong>for</strong> this oligomeric state. Significantly, we demonstrate <strong>for</strong> the first time, that
ScHSP26 also <strong>for</strong>ms larger oligomers, up to 40 subunits in size at room temperature. The oligomers observed
were exclusively composed <strong>of</strong> an even number <strong>of</strong> subunits. This strongly suggests there to be a basic dimeric
‘building block’, an observation consistent with the 3D structure <strong>of</strong> the ScHSP26 24mer, as well as studies
per<strong>for</strong>med on sHSPs from bacteria, plants and mammals. Using an online thermo-controlled device we
investigated the effect <strong>of</strong> heat stress on the oligomeric structure <strong>of</strong> ScHSP26. We found that as the
temperature was increased, dissociation <strong>of</strong> the oligomers into dimers and monomers was observed. Such
dissociation has previously been observed <strong>for</strong> ScHSP26 and other sHSPs. The remaining ScHSP26 existed in
<strong>for</strong>ms 32 subunits or larger, with the majority having assembled into a 40mer. There is a possibility that these
larger <strong>for</strong>ms are unusually resistant to thermal stress, or ScHSP26 preferentially associates into these <strong>for</strong>ms at
elevated temperatures.
1A_07_P
(poster section A1, poster board #10, 25 th <strong>of</strong> August)
SMALL HSPS FORM INTRACELLULAR GRANULES WITH AKT/PKB AND P38
DISTINCT FROM TIA/TIAR-CONTAİNİNG STRESS GRANULES
Anastassiia Vertii, Alexey Kotlyarov, Matthias Gaestel
From the Institute <strong>of</strong> Biochemistry, Medical School Hannover, Hannover 30625, Germany
Small heat shock proteins are rapidly phosphorylated in response to cellular stress upon activation <strong>of</strong> p38
kinase pathway. Phosphorylation occurs at Ser 15 and Ser 86 in mouse Hsp25 and at Ser 15 , Ser 78 and Ser 82 in
human Hsp27 resulting in changes in their oligomeric state. Stress causes accumulation <strong>of</strong> Hsp25/27 in an
insoluble fraction and <strong>for</strong>mation <strong>of</strong> intracellular granular structures. Although stress-induced Hsp27 granules
have been known <strong>for</strong> a long time, the presence <strong>of</strong> other proteins in these granules remains enigmatic. Certain
stress granules (SGs) contain mRNA-binding proteins, such as TIA/TIAR, and sequested processing bodies
with mRNA and translation initiation factors which play a role in translational inhibition. Here we report
stress-independent interaction between Hsp25 and Akt/PKB and characterised the regions in Hsp25 and Akt
responsible <strong>for</strong> this interaction. We further analysed stress-induced insolubilisation <strong>of</strong> small Hsps and
demonstrate stress-induced insolubilization <strong>of</strong> Akt together with Hsp25. By immun<strong>of</strong>luorescence we show
that Hsp25/27-containig SGs, which are <strong>for</strong>med in response to arsenite treatment <strong>of</strong> HeLa cells, include Akt
and p38. Although it is known that MK2 interacts with p38 we were not able to detect overexpressed MK2 in
these SGs. Furthermore, these SGs are distinct from cytoplasmic granules that contain TIA/TIAR. siRNA
silencing and nuclear/cytoplasmic fractionation was used to further describe the role <strong>of</strong> these novel SGs <strong>for</strong>
the function <strong>of</strong> Akt.
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