Induction of cell cycle regulatory proteins by murine B cell proliferating pectic polysaccharide from the roots of Bupleurum falcatum L.
Bupleuran 2IIc, a pectic polysaccharide isolated from the roots of Bupleurum falcatum L., was characterized as a T-cell-independent B cell mitogen, that activates, proliferates and differentiates B cells in vivo and in vitro (Immunology 97 (1999) 540). Studies were focused on elucidating the mechanism by which bupleuran 2IIc causes proliferation of B cells and expression of cell cycle regulatory proteins. B cells showed slower rates of entry into the S and G2/M phases of the cell cycle when stimulated with bupleuran 2IIc versus anti-IgM. However, the Stimulation Index continued up to two times longer with bupleuran 2IIc over anti-IgM. Although both bupleuran 2IIc and anti-IgM induced similar expressions of cell cycle regulatory proteins, cyclins D2, A, and B1, in B cells, those cells stimulated with bupleuran 2IIc appeared to sustain expressions of these protein for longer periods of time. Stimulation of B cells with bupleuran 2IIc induced phosphorylation of retinoblastoma protein, pRB, an important gene product regulating the restriction point, R, which is responsible for the transition from the G0/G1 to the S phases of the cell cycle. The results of this study demonstrate that both bupleuran 2IIc and anti-IgM interact with B cells, thus, leading to expressions of cell cycle regulatory proteins. However, the respective modes of binding and proximity of interactions with the B cell membrane may differ.
Matsumoto
Tsukasa
T
Kitasato Institute for Life Sciences and Graduate School of Infection Control Sciences, Kitasato University, 5-9-1 Shirokane, Minato-ku, 108-8641, Tokyo, Japan.
Guo
Ying-Jie
YJ
Ikejima
Takashi
T
Yamada
Haruki
H
D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology / Q000378:metabolism*; D029972:Bupleurum / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000096:biosynthesis / Q000235:genetics*; D002455:Cell Division / Q000276:immunology / Q000502:physiology; D005260:Female; D005786:Gene Expression Regulation; D007075:Immunoglobulin M / Q000276:immunology; D051379:Mice; D010368:Pectins / Q000378:metabolism*
D018797:Cell Cycle Proteins; D007075:Immunoglobulin M; C073829:Bupleuran 2IIc; D010368:Pectins