Chaperone-Like Activity of HSPB5: The Effects of Quaternary Structure Dynamics and Crowding

Abstract

Small heat-shock proteins (sHSPs) are ATP-independent molecular chaperones that interact with partially unfolded proteins, preventing their aberrant aggregation, thereby exhibiting a chaperone-like activity. Dynamics of the quaternary structure plays an important role in the chaperone-like activity of sHSPs. However, relationship between the dynamic structure of sHSPs and their chaperone-like activity remains insufficiently characterized. Many factors (temperature, ions, a target protein, crowding etc.) affect the structure and activity of sHSPs. The least studied is an effect of crowding on sHSPs activity. In this work the chaperone-like activity of HSPB5 was quantitatively characterized by dynamic light scattering using two test systems, namely test systems based on heat-induced aggregation of muscle glycogen phosphorylase b (Phb) at 48 °C and dithiothreitol-induced aggregation of α-lactalbumin at 37 °C. Analytical ultracentrifugation was used to control the oligomeric state of HSPB5 and target proteins. The possible anti-aggregation functioning of suboligomeric forms of HSPB5 is discussed. The effect of crowding on HSPB5 anti-aggregation activity was characterized using Phb as a target protein. The duration of the nucleation stage was shown to decrease with simultaneous increase in the relative rate of aggregation of Phb in the presence of HSPB5 under crowded conditions. Crowding may subtly modulate sHSPs activity.

Effect of Betaine and Arginine on Interaction of αB-Crystallin with Glycogen Phosphorylase b

“…Earlier we showed a significant increase in the size of αB-Cr at 48 °C under crowding conditions arising from the presence of 1 M TMAO and/or other crowding agents [ 39 ]. The estimated number of subunits in the αB-Cr oligomer increased from 22-mers up to 50-mers under conditions of mixed crowding created by 1M TMAO + PEG [ 34 , 39 ]. Grosas and colleagues also reported an increase in the size of αB-Cr under crowding conditions [ 40 ].…”

“…In this work, we studied the effect of Arg and Bet on αB-Cr and its PPIs with target protein and tried to determine the initial stoichiometry of the chaperone–client complex and the effect of Arg and Bet on this value at different stages of the enzyme aggregation. For the research, we chose a well-studied test system based on the thermal aggregation of glycogen phosphorylase b (Ph b ) at 48 °C [ 33 , 34 ]. Previously it was shown that Arg and Bet acted in opposite directions on Ph b aggregation.…”

Structural and functional studies of D109A human αB-crystallin contributing to the development of cataract and cardiomyopathy diseases

“…It is well known that a flexible dynamic structure is required for the functioning of αB-crystallin. The equilibrium between oligomeric forms is very sensitive to changes in the cellular environment and crowding conditions [ 47 , 48 ]. In the eye lenses, there is a very delicate pattern of interactions among α-crystallin and its other natural partners, such as beta- and gamma-crystallin [ 49 ], so that as a result of the structural alteration, a slightest change in these interactions is expected to cause important optical focusing problem, leading to development of the visual perturbation [ 43 – 46 ].…”

Regulation by Different Types of Chaperones of Amyloid Transformation of Proteins Involved in the Development of Neurodegenerative Diseases

“…Accordingly, it can be assumed that crowding conditions affect both the kinetics and thermodynamics of interactions between macromolecules, including protein folding and aggregation [ 119 , 120 , 121 ]. Since crowding has a strong effect on protein–protein interactions, its influence on the conformation and self-association of chaperones, interaction of chaperones with target proteins, and the aggregation of the target proteins should also be taken into account [ 122 ].…”