TY - JOUR
T1 - Association between bcl-xL and 5-lipoxygenase activating protein (FLAP) levels in IL-3-dependent FL5.12 cells
AU - Biswal, Shyam S.
AU - Datta, Kaushik
AU - Kehrer, James P.
N1 - Funding Information:
This work was supported by NIH grants HL51005 and CA83701. Support from NIEHS Center grant ES07784 is also acknowledged. JPK is the Gustavus and Louise Pfeiffer Professor of Toxicology. The authors are pleased to submit this paper to be published in this Toxicology, Festschrift in honor of its long time editor Peter Witschi, and whose friendship and mentorship of JPK for many years is greatly appreciated.
Copyright:
Copyright 2007 Elsevier B.V., All rights reserved.
PY - 2001/3/7
Y1 - 2001/3/7
N2 - The expression of 5-lipoxygenase activating protein (FLAP) in murine hematopoietic FL5.12 cells that are transfected to overexpress bcl-xL is less than in control cells. In addition, the withdrawal of IL-3 from the bcl-xL overexpressing cells, but not control cells, leads to the rapid loss of FLAP even though these cells, in contrast to control cells, do not undergo apoptosis (Datta et al., J. Biol. Chem. 273, 28163-28169 [1998]). The mechanism(s) underlying these observations is not known. Basal FLAP mRNA levels were actually 2.8-fold higher in bcl-xL than control cells indicating that this difference does not have a transcription basis. In addition, an examination of FLAP mRNA levels in response to withdrawal of IL-3 revealed a 2-3-fold increase after 4 and 8 h relative to time-matched samples in both control and bcl-xL overexpressing cells. This further indicates that the decrease in FLAP levels in bcl-xL overexpressing cells is not related to transcription and suggests an attempt at compensation perhaps in response to increased FLAP degradation/turnover. A proteolytic mechanism was explored by examining the effect of the general caspase inhibitor Boc-D-FMK, and the non-caspase protease inhibitors phenylmethylsulfonyl fluoride (PMSF), pepstatin and leupeptin, on the loss of FLAP in bcl-xL overexpressing cells subsequent to IL-3 withdrawal. All inhibitors provided some protection from the loss of FLAP, with PMSF being the most effective, actually increasing FLAP levels above those seen in untreated cells. Given the absence of apoptosis in bcl-xL cells, it appears that protease activation is an effect that can accompany a variety of cellular perturbations. The functional consequences of a loss of FLAP in growth-factor deprived cells overexpressing bcl-xL is not known. However, these data continue to suggest some link between bcl-xL and FLAP.
AB - The expression of 5-lipoxygenase activating protein (FLAP) in murine hematopoietic FL5.12 cells that are transfected to overexpress bcl-xL is less than in control cells. In addition, the withdrawal of IL-3 from the bcl-xL overexpressing cells, but not control cells, leads to the rapid loss of FLAP even though these cells, in contrast to control cells, do not undergo apoptosis (Datta et al., J. Biol. Chem. 273, 28163-28169 [1998]). The mechanism(s) underlying these observations is not known. Basal FLAP mRNA levels were actually 2.8-fold higher in bcl-xL than control cells indicating that this difference does not have a transcription basis. In addition, an examination of FLAP mRNA levels in response to withdrawal of IL-3 revealed a 2-3-fold increase after 4 and 8 h relative to time-matched samples in both control and bcl-xL overexpressing cells. This further indicates that the decrease in FLAP levels in bcl-xL overexpressing cells is not related to transcription and suggests an attempt at compensation perhaps in response to increased FLAP degradation/turnover. A proteolytic mechanism was explored by examining the effect of the general caspase inhibitor Boc-D-FMK, and the non-caspase protease inhibitors phenylmethylsulfonyl fluoride (PMSF), pepstatin and leupeptin, on the loss of FLAP in bcl-xL overexpressing cells subsequent to IL-3 withdrawal. All inhibitors provided some protection from the loss of FLAP, with PMSF being the most effective, actually increasing FLAP levels above those seen in untreated cells. Given the absence of apoptosis in bcl-xL cells, it appears that protease activation is an effect that can accompany a variety of cellular perturbations. The functional consequences of a loss of FLAP in growth-factor deprived cells overexpressing bcl-xL is not known. However, these data continue to suggest some link between bcl-xL and FLAP.
KW - 5-Lipoxygenase activating protein
KW - Proteases
KW - bcl Proteins
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U2 - 10.1016/S0300-483X(00)00442-X
DO - 10.1016/S0300-483X(00)00442-X
M3 - Article
C2 - 11246129
AN - SCOPUS:0035819892
SN - 0300-483X
VL - 160
SP - 97
EP - 103
JO - Toxicology
JF - Toxicology
IS - 1-3
ER -