Association between bcl-xL and 5-lipoxygenase activating protein (FLAP) levels in IL-3-dependent FL5.12 cells

Shyam Biswal, Kaushik Datta, James P. Kehrer

Research output: Contribution to journalArticle

Abstract

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.

Original languageEnglish (US)
Pages (from-to)97-103
Number of pages7
JournalToxicology
Volume160
Issue number1-3
DOIs
StatePublished - Mar 7 2001
Externally publishedYes

Fingerprint

5-Lipoxygenase-Activating Proteins
Interleukin-3
Phenylmethylsulfonyl Fluoride
Transcription
Apoptosis
Messenger RNA
Caspase Inhibitors
Protease Inhibitors
Intercellular Signaling Peptides and Proteins
Peptide Hydrolases
Chemical activation
Degradation

Keywords

  • 5-Lipoxygenase activating protein
  • bcl Proteins
  • Proteases

ASJC Scopus subject areas

  • Toxicology

Cite this

Association between bcl-xL and 5-lipoxygenase activating protein (FLAP) levels in IL-3-dependent FL5.12 cells. / Biswal, Shyam; Datta, Kaushik; Kehrer, James P.

In: Toxicology, Vol. 160, No. 1-3, 07.03.2001, p. 97-103.

Research output: Contribution to journalArticle

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abstract = "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.",
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