The Hsp110 protein chaperone Sse1 is required for yeast cell wall integrity and morphogenesis.

Molecular chaperones direct refolding and triage decisions and support signal transduction responses to cytotoxic stress. The eukaryotic chaperone Hsp110 is represented by the SSE1/2 genes in Saccharomyces cerevisiae, which act as nucleotide exchange factors (NEFs) for cognate cytosolic Hsp70 chaperones. In this report, we present evidence that Sse1 is required for signaling through the cell integrity pathway via partnership with Hsp90 and the terminal MAP kinase Slt2.

All in the family: atypical Hsp70 chaperones are conserved modulators of Hsp70 activity.

Divergent relatives of the Hsp70 protein chaperone such as the Hsp110 and Grp170 families have been recognized for some time, yet their biochemical roles remained elusive. Recent work has revealed that these "atypical" Hsp70s exist in stable complexes with classic Hsp70s where they exert a powerful nucleotide-exchange activity that synergizes with Hsp40/DnaJ-type cochaperones to dramatically accelerate Hsp70 nucleotide cycling. This represents a novel evolutionary transition from an independent protein-folding chaperone to what appears to be a dedicated cochaperone.

Characterization of Hsp70 binding and nucleotide exchange by the yeast Hsp110 chaperone Sse1.

SSE1 and SSE2 encode the essential yeast members of the Hsp70-related Hsp110 molecular chaperone family. Both mammalian Hsp110 and the Sse proteins functionally interact with cognate cytosolic Hsp70s as nucleotide exchange factors. We demonstrate here that Sse1 forms high-affinity (Kd approximately 10-8 M) heterodimeric complexes with both yeast Ssa and mammalian Hsp70 chaperones and that binding of ATP to Sse1 is required for binding to Hsp70s.

The yeast Hsp110 Sse1 functionally interacts with the Hsp70 chaperones Ssa and Ssb.

There is growing evidence that members of the extended Hsp70 family of molecular chaperones, including the Hsp110 and Grp170 subgroups, collaborate in vivo to carry out essential cellular processes. However, relatively little is known regarding the interactions and cellular functions of Sse1, the yeast Hsp110 homolog. Through co-immunoprecipitation analysis, we found that Sse1 forms heterodimeric complexes with the abundant cytosolic Hsp70s Ssa and Ssb in vivo.

The molecular chaperone Sse1 and the growth control protein kinase Sch9 collaborate to regulate protein kinase A activity in Saccharomyces cerevisiae.

The Sch9 protein kinase regulates Hsp90-dependent signal transduction activity in the budding yeast Saccharomyces cerevisiae. Hsp90 functions in concert with a number of cochaperones, including the Hsp110 homolog Sse1. In this report, we demonstrate a novel synthetic genetic interaction between SSE1 and SCH9.