title: Regulation of Bruton tyrosine kinase by the peptidylprolyl isomerase Pin1.
abstract: Bruton tyrosine kinase (Btk) is expressed in B-lymphocytes. Mutations in Btk cause X-linked agammaglobulinemia in humans. However, the mechanism of activation and signaling of this enzyme has not been fully investigated. We have here shown that the peptidylprolyl cis/trans isomerase (PPIase) Pin1 is a negative regulator of Btk, controlling its expression level by reducing its half-life, whereas the catalytic activity of Btk was unaffected. The negative regulatory effect of Pin1 was observed both in cell lines and in Pin(-/-) mice and was found to be dependent on a functionally intact Btk. This may constitute a feedback loop for the regulation of Btk. The target region in Btk was localized to the pleckstrin homology domain suggesting that interphase phosphorylation of serine 115 (Ser-115) in Btk is required, whereas mitosis phosphorylation of serine 21 (Ser-21) is critical. Accordingly, Pin 1 was shown to associate with Btk through binding to Ser-21 and -115, respectively, both of which lie in a classical Pin1-binding pocket. Using a phosphomitotic antibody, it was found that Btk harbors a bona fide MPM2 epitope corresponding to a phosphorylated serine or threonine residue followed by a proline. Our results indicate that the peptidylprolyl isomerase Pin1 interacts with Btk in a cell cycle-dependent manner, regulating the Btk expression level.
authors.affiliation: Department of Laboratory Medicine, Clinical Research Center, Karolinska Institutet, SE-4186 Stockholm, Sweden.
authors.forename: Liang
authors.initials: L
authors.lastname: Yu
authors.forename: Abdalla J
authors.initials: AJ
authors.lastname: Mohamed
authors.forename: Leonardo
authors.initials: L
authors.lastname: Vargas
authors.forename: Anna
authors.initials: A
authors.lastname: Berglöf
authors.forename: Greg
authors.initials: G
authors.lastname: Finn
authors.forename: Kun Ping
authors.initials: KP
authors.lastname: Lu
authors.forename: C I Edvard
authors.initials: CI
authors.lastname: Smith
mesh_terms: D000077329:Agammaglobulinaemia Tyrosine Kinase; D000818:Animals; D001402:B-Lymphocytes / Q000201:enzymology; D019556:COS Cells; D045744:Cell Line, Tumor; D002522:Chlorocebus aethiops; D006224:Cricetinae; D004789:Enzyme Activation; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D007668:Kidney / Q000166:cytology; D007938:Leukemia; D008247:Lysosomes / Q000201:enzymology; D008407:Mast Cells / Q000166:cytology; D051379:Mice; D008817:Mice, Mutant Strains; D041681:NIH 3T3 Cells; D000072340:NIMA-Interacting Peptidylprolyl Isomerase; D019696:Peptidylprolyl Isomerase / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000235:genetics* / Q000378:metabolism*; D051381:Rats; D014443:Tyrosine / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D000072340:NIMA-Interacting Peptidylprolyl Isomerase; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D000077329:Agammaglobulinaemia Tyrosine Kinase; C000625949:BTK protein, human; C000625951:Btk protein, mouse; D046988:Proteasome Endopeptidase Complex; C000606846:PIN1 protein, human; D019696:Peptidylprolyl Isomerase; C000606850:Pin1 protein, mouse