Temperature-dependent oligomerization of hsp85 in vitro

Area of Science:

• Cellular Biology
• Molecular Biology
• Stress Response

Background:

• Conventional subcellular fractionation methods fail to detect interactions of heat shock protein 85 (hsp85) with cellular structures.
• Critical stress protein interactions may only be detectable at elevated temperatures.

Purpose of the Study:

• To investigate the temperature-dependent interactions of hsp85 with cellular structures.
• To determine the role of detergent in hsp85 complex formation at elevated temperatures.

Main Methods:

• Analysis of protein sedimentation in Triton X-100 extracts of L929 cells across a temperature range (30-43°C).
• Comparison of hsp85 sedimentation with other heat shock proteins (hsp110, hsp69).
• Investigation of temperature-dependent oligomerization of purified hsp85 in the presence of detergent.

Main Results:

• hsp85 and grp95 incorporation into sedimentable complexes increased progressively from 30°C to 43°C.
• hsp85 became sedimentable at 33°C, a lower temperature than hsp110 and hsp69 (approx. 43°C).
• hsp85 sedimentation was highly detergent-dependent, suggesting limited oligomerization in the presence of detergent.

Conclusions:

• hsp85 oligomerization is temperature-dependent and occurs at lower temperatures compared to other heat shock proteins.
• Detergent facilitates hsp85 oligomerization, suggesting this may occur in intact cells exposed to elevated temperatures.
• Sphingosine can fulfill the detergent requirement for hsp85 oligomerization.