Oligomer-dependent and -independent chaperone activity of sHsps in different stressed conditions

• Acid stress induces dissociation of Hsp20.1 and Hsp14.1 oligomers.
• Dissociated Hsp20.1 and Hsp14.1 show chaperone activities in acid stress.
• Hsp20.1 and Hsp14.1 maintain oligomers and show chaperone activities at 50 °C.
• sHsps might function in different modes in different stressed conditions.

A great number of studies have proven that sHsps protect cells by inhibiting protein aggregation under heat stress, while little is known about their function to protect cells under acid stress. In this work, we show that Hsp20.1 and Hsp14.1 oligomers dissociated to smaller oligomeric species or even dimer/monomer at low pH (pH 4.0 and pH 2.0), whereas no prominent quaternary structural changes were seen at 50 °C. Both oligomers and smaller oligomeric species exhibited abilities to suppress client aggregation at low pH and at 50 °C. These results suggest that sHsps may function in different modes in different stressed conditions.