title: Stevastelins, a novel group of immunosuppressants, inhibit dual-specificity protein phosphatases.
abstract: BACKGROUND
  Since the molecular target of the immunosuppressive reagents FK506 and cyclosporin A was revealed to be protein phosphatase PP2B (calcineurin), many researchers have been screening the protein phosphatase inhibitors from microbial metabolites to develop new immunosuppressive reagents. We isolated stevastelin B, which is composed of valine, threonine, serine and 3,5-dihydroxy-2,4-dimethyl stearic acid, and stevastelin A, which is a sulphonylated derivative of stevastelin B. To understand the action mechanism of stevastelins A and B, we synthesized a series of stevastelin derivatives and investigated their structure-activity relationships.
  
  
  RESULTS
  A series of stevastelin derivatives have been systematically synthesized. Stevastelin B inhibited gene expression that is dependent on interleukin-2 (IL-2) or IL-6 promoters in situ, but it had no inhibitory activity against any protein phosphatases in vitro. In contrast, stevastelin A, which is a sulphonylated derivative of stevastelin B, inhibited the phosphatase activity of a dual-specificity phosphatase, VH1-related human protein (VHR), in vitro, but it had no inhibitory activity against gene expression or cell-cycle progression in situ.
  
  
  CONCLUSIONS
  Stevastelin B is a novel immunosuppressant. It inhibited IL-2 or IL-6 dependent gene expression but did not inhibit the phosphatase activity of calcineurin. The structure-activity relationships show that the acidic functional group on the threonine residue and the stearic acid moiety in the stevastelin molecule are important for inhibitory effects on the dephosphorylation activity of VHR in vitro. Stevastelin B might be sulphonylated or phosphorylated after incorporation into the target cell, and then it interacts with protein tyrosine phosphatases and regulates cell-cycle progression.
authors.affiliation: Antibiotics Laboratory, The Institute of Physical and Chemical Research (RIKEN), Hirosawa 2-1, Wako-shi, Saitama, 351-01, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Hamaguchi
authors.forename: A
authors.initials: A
authors.lastname: Masuda
authors.forename: T
authors.initials: T
authors.lastname: Morino
authors.forename: H
authors.initials: H
authors.lastname: Osada
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D015153:Blotting, Western; D002453:Cell Cycle / Q000187:drug effects; D047630:Depsipeptides; D054640:Dual Specificity Phosphatase 3; D005434:Flow Cytometry; D005656:Fungal Proteins; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D007166:Immunosuppressive Agents / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D007378:Interleukins / Q000235:genetics; D015394:Molecular Structure; D010455:Peptides; D010456:Peptides, Cyclic / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors*; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors*; D013329:Structure-Activity Relationship; D014407:Tumor Cells, Cultured
chemical_list: D000900:Anti-Bacterial Agents; D047630:Depsipeptides; D005656:Fungal Proteins; D007166:Immunosuppressive Agents; D007378:Interleukins; D010455:Peptides; D010456:Peptides, Cyclic; D010750:Phosphoproteins; C100705:stevastelin B; C100704:stevastelin A; D010749:Phosphoprotein Phosphatases; C517025:DUSP3 protein, human; D054640:Dual Specificity Phosphatase 3; D017027:Protein Tyrosine Phosphatases