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

Natalia A Chebotareva,Tatiana B Eronina,Svetlana G Roman,Valeriya V Mikhaylova,Vera A Borzova,Boris I Kurganov

doi:10.3390/ijms21144940

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.

Highlights

ΑB-Crystallin belongs to a superfamily of small heat shock proteins, which are ubiquitously expressed and play an important role in maintaining cellular proteostasis [1]. sHSPs bind non-native and misfolded proteins, keeping them from further aggregation and protecting the cell from toxic aggregates [1,2,3,4,5]
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
Benesh and colleagues [90] suggested that the quaternary structure of α-crystallins is modulated by the assembly of oligomers from monomers or from dimers and there is an exchange between these forms, that have different conformation and chaperone-like activity [90]

Summary

Introduction

ΑB-Crystallin belongs to a superfamily of small heat shock proteins (sHSPs), which are ubiquitously expressed and play an important role in maintaining cellular proteostasis [1]. sHSPs bind non-native and misfolded proteins, keeping them from further aggregation and protecting the cell from toxic aggregates [1,2,3,4,5]. ΑB-Crystallin belongs to a superfamily of small heat shock proteins (sHSPs), which are ubiquitously expressed and play an important role in maintaining cellular proteostasis [1]. SHSPs bind non-native and misfolded proteins, keeping them from further aggregation and protecting the cell from toxic aggregates [1,2,3,4,5]. [4,8,9,10] Given these significant biological roles, the dysregulation of sHSPs is associated with cancer [11], cataract formation [12,13,14], and neurodegenerative diseases [5,10]. The processes of regulation of the functioning of sHSPs are very important. HSPB5 is widespread in all tissues, but its concentration in the eye lens is especially high (400 mg/mL), where it interacts with αA-crystallin (HSPB4) and forms a native hetero-oligomeric complex, α-crystallin [16]

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