title: Phosphorylation of serine 523 on 5-lipoxygenase in human B lymphocytes.
abstract: The key enzyme in leukotriene (LT) biosynthesis is 5-lipoxygenase (5-LO), which is expressed in myeloid cells and in B lymphocytes. There are three phosphorylation sites on 5-LO (Ser271, Ser523 and Ser663). Protein kinase A (PKA) phosphorylates 5-LO on Ser523. In this report, we demonstrate by immunoblotting that native 5-LO in mantle B cell lymphoma (MCL) cells (Granta519, JEKO1, and Rec1) and in primary chronic B lymphocytic leukemia cells (B-CLL) is phosphorylated on Ser523. In contrast, we could not detect phosphorylation of 5-LO on Ser523 in human granulocytes or monocytes. Phosphorylated 5-LO was purified from Rec1 cells, using an ATP-agarose column, and the partially purified enzyme could be dephosphorylated with alkaline phosphatase. Incubation of Rec1 cells with 8-Br-cAMP or prostaglandin E2 stimulated phosphorylation at Ser523. Furthermore, FLAG-5LO was expressed in Rec1 cells, and the cells were cultivated in the presence of 8-Br-cAMP. The 5-LO protein from these cells was immunoprecipitated, first with anti-FLAG, followed by anti-pSer523-5-LO. The presence of 5-LO protein in the final precipitate further supported the finding that the protein recognized by the pSer523 antibody was 5-LO. Taken together, this study shows that 5-LO in B cells is phosphorylated on Ser523 and demonstrates for the first time a chemical difference between 5-LO in myeloid cells and B cells.
authors.affiliation: Department of Medical Biochemistry and Biophysics, Karolinska Institutet, 171 77 Stockholm, Sweden.
authors.forename: Yilmaz
authors.initials: Y
authors.lastname: Mahshid
authors.affiliation: Institute of Pharmaceutical Chemistry/ZAFES, Goethe-University, 60438 Frankfurt am Main, Germany.
authors.forename: Stavroula
authors.initials: S
authors.lastname: Markoutsa
authors.affiliation: Department of Medical Biochemistry and Biophysics, Karolinska Institutet, 171 77 Stockholm, Sweden.
authors.forename: Vildan
authors.initials: V
authors.lastname: Dincbas-Renqvist
authors.affiliation: University of Frankfurt Medical School, Department of Molecular Hematology, 60590 Frankfurt am Main, Germany.
authors.forename: Duran
authors.initials: D
authors.lastname: Sürün
authors.affiliation: Department of Laboratory Medicine, Division of Pathology, Karolinska University Hospital Huddinge and Karolinska Institutet, 141 86 Stockholm, Sweden.
authors.forename: Birger
authors.initials: B
authors.lastname: Christensson
authors.affiliation: Department of Laboratory Medicine, Division of Pathology, Karolinska University Hospital Huddinge and Karolinska Institutet, 141 86 Stockholm, Sweden.
authors.forename: Birgitta
authors.initials: B
authors.lastname: Sander
authors.affiliation: Department of Medicine, Karolinska Hospital Solna and Karolinska Institutet, 171 76 Stockholm, Sweden.
authors.forename: Magnus
authors.initials: M
authors.lastname: Björkholm
authors.affiliation: Institute of Pharmaceutical Chemistry/ZAFES, Goethe-University, 60438 Frankfurt am Main, Germany.
authors.forename: Bernd L
authors.initials: BL
authors.lastname: Sorg
authors.affiliation: Department of Medical Biochemistry and Biophysics, Karolinska Institutet, 171 77 Stockholm, Sweden.
authors.forename: Olof
authors.initials: O
authors.lastname: Rådmark
authors.affiliation: Department of Medicine, Karolinska Hospital Solna and Karolinska Institutet, 171 76 Stockholm, Sweden. Electronic address: hans-erik.claesson@ki.se.
authors.forename: Hans-Erik
authors.initials: HE
authors.lastname: Claesson
mesh_terms: D001094:Arachidonate 5-Lipoxygenase / Q000378:metabolism*; D001402:B-Lymphocytes / Q000378:metabolism*; D045744:Cell Line, Tumor; D000242:Cyclic AMP / Q000378:metabolism; D006801:Humans; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000378:metabolism* / Q000473:pathology; D020522:Lymphoma, Mantle-Cell / Q000378:metabolism* / Q000473:pathology; D022423:Myeloid Cells / Q000378:metabolism; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D010766:Phosphorylation; D012694:Serine / Q000378:metabolism*
chemical_list: D012694:Serine; D000242:Cyclic AMP; D001094:Arachidonate 5-Lipoxygenase; D010744:Phosphoric Monoester Hydrolases
keywords: Arachidonic acid; Cyclic AMP; Leukotriene; Lipoxygenase; Mantle cell lymphoma