Phosphorylation of Hsp90β on serine residues in the charged linker modulates binding to interacting proteins and has implications for overall Hsp90β conformation (Occupancy and phospho-modulation data)

Human Hsp90β is constitutively phosphorylated in vivo on two serine residues in the charged linker region, S226 and S255. We developed a targeted method to measure the phosphorylation occupancy (the extent of phosphorylation) of both phosphosites in a range of cultured cell lines and consistently found high occupancy (>90%) in the cytoplasm and nucleus. However, we found decreased phosphorylation, especially for S255, in Hsp90β purified from the conditioned medium of cultured K562 cells. In addition, we investigated if various cell growth conditions known to impact Hsp90β activity had an effect on the phosphorylation status of S226 and S255, but none of the conditions tested (e.g. heat shock, Hsp90β inhibition) resulted in an alteration of S226 and S255 phosphorylation.