Small heat shock protein Hsp20 (HspB6) as a partner of 14-3-3γ

Abstract

Interaction of human 14-3-3gamma with the small heat shock protein Hsp20 was analyzed by means of size-exclusion chromatography and chemical crosslinking. Unphosphorylated Hsp20 and its mutant S16D mimicking phosphorylation by cAMP-dependent protein kinase did not interact with 14-3-3. Phosphorylated Hsp20 formed a tight complex with 14-3-3 in which dimer of 14-3-3 was bound to dimer of Hsp20. 14-3-3 did not affect the chaperone activity of unphosphorylated Hsp20 but increased the chaperone activity of phosphorylated Hsp20 if insulin was used as a model substrate. Estimation of the effect of 14-3-3 on the chaperone activity of Hsp20 with other model substrates was complicated by the fact that under in vitro conditions isolated 14-3-3 possessed its own high chaperone activity. Taken into account high content of Hsp20 in different muscles it is supposed that upon phosphorylation Hsp20 might effectively compete with multiple protein targets of 14-3-3 and by this means indirectly affect many intracellular processes.

Small Heat-Shock Proteins: Paramedics of the Cell

“…Primary to these is heat shock, with sHSPs generally thought to be more effective chaperones at elevated temperature. For example, HSP26 has been demonstrated to undergo significant structural and dynamical changes around 40 C, consistent with a thermal activation of the protein [83,100,109]. While HSP26 is unusual in containing a middle domain, HSP18.1 undergoes a similar dynamic transition in oligomerisation from an inactive "storage form" into a functional chaperone with temperature [111].…”

“…In some members of the sHSP family, e.g. human HSP20 [40] and Taenia saginata TSP36 [36], the entire C-terminal region is absent. The N-terminal region is however essentially omnipresent and, in the main, considerably longer.…”

Modulators of Protein–Protein Interactions

“…109,110 HSPB6 dimerizes via its highly conserved α-Crystallin domain (ACD) that forms a β-sandwich, whereas both the N-terminal domain and C-terminal extension (NTD and CTE) that flank this region are highly unstructured. The interaction motif for 14-3-3 consists of a classical RRApSAP pattern located in the NTD.…”

Actin cytoskeletal dynamics in smooth muscle: a new paradigm for the regulation of smooth muscle contraction

“…Phosphopeptide analogs of HSP20 induce the relaxation of several different smooth muscle tissues and cell types (46,49,76,103,137). In vitro, phosphorylated HSP20 interacts directly with 14-3-3, the chaperone protein that sequesters cofilin (26). Brophy and colleagues have proposed that HSP20 mediates smooth muscle relaxation in response to cyclic nucleotidedependent pathways by competing with phosphocofilin for binding to the chaperone protein, 14-3-3, leading to an increase in the amount of activated cofilin (46,76).…”