A possible signal transduction pathway for cyclin D2 expression by a pectic polysaccharide from the roots of bupleurum falcatum L. in murine B cell.
Bupleuran 2IIc, a pectic polysaccharide isolated from the roots of bupleurum falcatum L., was previously characterized as a T-cell-independent B cell mitogen. This study focuses on elucidating the mechanism by which bupleuran 2IIc induces cyclin D2 production for inducing mitogenesis in murine B cells. Bupleuran 2IIc was digested with endo-alpha-(1-->4)-D-polygalacturonase and the resulting bupleuran 2IIc/PG-1 ("ramified" region) strongly stimulated cyclin D2 expression. When murine B cells were stimulated with bupleuran 2IIc/PG-1, phosphorylation of tyrosine residues of a number of proteins was observed. Cyclin D2 expression by bupleuran 2IIc/PG-1 was inhibited by the tyrosine kinase inhibitors, genistein and herbimycin A, and the Src family tyrosine kinase inhibitor, PP2, suggesting a possible role for tyrosine kinases. The stimulation by bupleuran 2IIc/PG-1 of cyclin D2 expression was significantly decreased by inhibitors, PI 3-kinase (LY294002 and Wortmannin), PLCgamma (U73122), PKC (H-7), receptor-operated calcium entry inhibitor (SK&F 96365), and calcineurin (FK506). Both PD98059 and U0126, highly selective inhibitors of MEK1 and MEK1/2, respectively, did not strongly suppress the expression of cyclin D2 after stimulation by bupleuran 2IIc/PG-1. The results suggest that (1) bupleuran 2IIc/PG-1 is the active site for induction of cyclin D2 by bupleuran 2IIc, (2) the expression of the cyclin D2 gene by bupleuran 2IIc/PG-1 may be mediated via the activation of PI 3-kinase and PLCgamma followed by activation of PKC and calcium mobilization, and (3) the ERK1/2 cascade is not a central signaling pathway for bupleuran 2IIc/PG-1-induced cyclin D2 expression.
Matsumoto
Tsukasa
T
Kitasato Institute for Life Sciences and Graduate School of Infection Control Sciences, Kitasato University, 5-9-1 Shirokane, Minato, Tokyo 108-8641, Japan.
Hosono-Nishiyama
Kanako
K
Guo
Ying-Jie
YJ
Ikejima
Takashi
T
Yamada
Haruki
H
D000818:Animals; D001402:B-Lymphocytes / Q000187:drug effects* / Q000201:enzymology / Q000276:immunology; D002118:Calcium / Q000378:metabolism; D002240:Carbohydrate Sequence; D056742:Cyclin D2; D016213:Cyclins / Q000096:biosynthesis*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D008213:Lymphocyte Activation; D051379:Mice; D008969:Molecular Sequence Data; D010368:Pectins / Q000096:biosynthesis / Q000737:chemistry / Q000494:pharmacology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D051966:Phospholipase C gamma; D011493:Protein Kinase C / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D010738:Type C Phospholipases / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
C486196:Ccnd2 protein, mouse; D056742:Cyclin D2; D016213:Cyclins; D004791:Enzyme Inhibitors; C073829:Bupleuran 2IIc; D010368:Pectins; D019869:Phosphatidylinositol 3-Kinases; D011505:Protein-Tyrosine Kinases; D011493:Protein Kinase C; D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D010738:Type C Phospholipases; D051966:Phospholipase C gamma; D002118:Calcium