Fig. 6.
sHSPs establish a disperse chaperone network. A The dodecameric form of HSP18.1 represents a “storage” form, which is in equilibrium with suboligomeric species, and, through recombination with these, higher-order oligomers. These higher-order species are themselves continually recycling through the loss and reincorporation of dimers and monomers. Upon heat-shock the equilibria shift (Red) from the dodecamer to dissociated species, and unfolding clients are bound to form sHSP:client complexes. B From the number of different species we observe here for the different states of HSP18.1 (Orange) we can extrapolate to systems incorporating multiple sHSPs (Bars). Based on the ability of related sHSPs to hetero-oligomerise, the number of potential species (NComb) can be calculated using the inset equation, where NsHSP is the number of compatible sHSPs, i the number of HSP18.1 subunits in the oligomer, and NClient the number of different bound states for a particular i. This reveals a remarkably extensive potential sHSP network, presumably catering for the array of different unfolding clients requiring protection from aggregation during cellular stress.