Apolipoprotein D gene induction by retinoic acid is concomitant with growth arrest and cell differentiation in human breast cancer cells

Stationary phase expression of a novel Escherichia coli outer membrane lipoprotein and its relationship with mammalian apolipoprotein D. Implications for the origin of lipocalins

We report a novel outer membrane lipoprotein of Escherichia coli. DNA sequencing between ampC and sugE at the 94.5 min region of the E. coli chromosome revealed an open reading frame specifying 177 amino acid residues. Primer extension analysis demonstrated that the promoter is activated at the transition between exponential and stationary growth phases under control of the rpoS sigma factor gene, and this was confirmed in vivo by monitoring expression of beta-galactosidase activity from a lacZ translational fusion. The amino acid sequence exhibited 31% identity with human apolipoprotein D (apoD), which is a component of plasma high density lipoprotein and belongs to the eukaryotic family of lipocalins. The bacterial lipocalin (Blc) contained a short deletion of 7 amino acid residues corresponding to a hydrophobic surface loop that is thought to facilitate the physical interaction between apoD and high density lipoprotein. However, Blc exhibited a typical prokaryotic lipoprotein signal peptide at its amino terminus. Overexpression, membrane fractionation, and metabolic labeling with [3H]palmitate demonstrated that Blc is indeed a globomycin-sensitive outer membrane lipoprotein. Blc represents the first bacterial member of the family of lipocalins and may serve a starvation response function in E. coli.

Interleukin-6 inhibits the potent stimulatory action of androgens, glucocorticoids and interleukin-1 alpha on apolipoprotein D and GCDFP-15 expression in human breast cancer cells

Our study was designed to investigate the potential interaction between steroid hormones and interleukin-6 (IL-6) in the regulation of apolipoprotein D (apo-D) and gross cystic disease fluid protein 15 (GCDFP-15) expression in ZR-75-1 human breast cancer cells. We first observed that exposure to IL-6 for 6-14 days decreased basal apo-D and GCDFP-15 secretion by 50% and 23%, respectively. In the same experiment, such treatment with IL-6 decreased cell proliferation by approximately 40% after 6 and 14 days of incubation. Exposure to IL-6 markedly decreased dihydrotestosterone (DHT)-induced apo-D and GCDFP-15 release, with a half-maximal effect measured at 13 U/ml. A similar inhibitory action of IL-6 was observed on the glucocorticoid dexamethasone (DEX)-induced apo-D and GC-DFP-15 secretion. The sensitivity of the apo-D and GCDFP-15 response to the stimulatory action of DHT or DEX was, however, not changed by concomitant exposure to IL-6. The inhibitory effect of IL-6 on the secretion of these two biochemical markers was additive to that of 17 beta-estradiol. In addition, IL-6 blocked the stimulatory effect of interleukin-1 alpha (IL-1 alpha) on apo-D and GCDFP-15 secretion. Our results show that IL-6 is a potent inhibitory of basal as well as androgen-, glucocorticoid- and IL-1 alpha-induced apo-D and GCDFP-15 secretion in ZR-75-1 human breast cancer cells, while cell proliferation is inhibited by this cytokine.

Cloning and expression analysis of a novel human serine hydrolase with sequence similarity to prokaryotic enzymes involved in the degradation of aromatic compounds

A full-length cDNA coding for a novel human serine hydrolase has been cloned from a breast carcinoma cDNA library. Nucleotide sequence analysis has shown that the isolated cDNA contains an open reading frame coding for a polypeptide of 274 amino acids and a complete Alu repetitive sequence within its 3'-untranslated region. The predicted amino acid sequence contains the Gly-X-Ser-X-Gly motif characteristic of serine hydrolases and displays extensive similarity to several prokaryotic hydrolases involved in the degradation of aromatic compounds. The highest degree of identities was detected with four serine hydrolases encoded by the bphD genes of different strains of Pseudomonas with the ability to degrade biphenyl derivatives. On the basis of these sequence similarities, this novel human enzyme has been tentatively called Biphenyl hydrolase-related protein (Bph-rp). The Bph-rp cDNA was expressed in Escherichia coli, and after purification, the recombinant protein was able to degrade p-nitrophenylbutyrate, a water-soluble substrate commonly used for assaying serine hydrolases. This hydrolytic activity was abolished by diisopropyl fluorophosphate, a covalent inhibitor of serine hydrolases, providing additional evidence that the isolated cDNA encodes a member of this protein superfamily. Northern blot analysis of poly(A)+ RNAs isolated from a variety of human tissues revealed that Bph-rp is mainly expressed in liver and kidney, which was also confirmed at the protein level by Western blot analysis with antibodies raised against purified recombinant Bph-rp. According to structural characteristics, hydrolytic activity and tissue distribution of Bph-rp, a potential role of this enzyme in detoxification processes is proposed.