Metabolism and signaling activities of nuclear lipids

Apart from the lipids present in the nuclear envelope, the nucleus also contains lipids which are located further inside and are resistant to treatment with nonionic detergents. Evidence is being accumulated on the importance of internal nuclear lipid metabolism. Nuclear lipid metabolism gives rise to several lipid second messengers that function within the nucleus. Moreover, it is beginning to emerge that nuclear lipids not only act as precursors of bioactive second messengers but may be directly involved in regulation of nuclear structure and gene expression. Over the last 10 years, especially the role of the inositol lipid cycle in nuclear signal transduction has been extensively studied. This cycle is activated following a variety of stimuli and is regulated independently from the inositide cycle located at the plasma membrane. However, the nucleus contain other lipids, such as phosphatidylcholine, sphingomyelin, fatty acids and eicosanoids. There are numerous reports which suggest that these classes of nuclear lipids may play roles in the nucleus as important as those of phosphoinositides. This review aims at highlighting the most important aspects regarding the metabolism and signaling activities of nuclear phosphatidylcholine, sphingomyelin, fatty acids and eicosanoids

Phosphoinositide 3-kinase/Akt involvement in arsenic trioxide resistance of human leukemia cells.

none8The purpose of this study was to evaluate the possible involvement of the phosphoinositide 3-kinase (PI3K)/Akt survival pathway in determining resistance to arsenic trioxide (As2O3)-induced apoptosis. We employed a HL60 cell clone (HL60AR) with a constitutively active PI3K/Akt survival pathway, as well as U937 and K562 cells. In addition, we used parental (PT) HL60 cells overexpressing a constitutively active Akt. Selective pharmacological inhibitors of the PI3K/Akt axis (LY294002, wortmannin) were employed to influence the sensitivity to As2O3. While HL60PT cells were sensitive to 2.5 mMAs2O3 and died of apoptosis, HL60AR cells were resistant up to 5 mM As2 O3. Treatment with either LY294002 or wortmannin lowered resistance of HL60AR cells to As2O3. Also in U937 and K562 cells, inhibitors of the PI3K/Akt axis caused a decrease in As2O3 resistance. Overexpression of constitutively active Akt in HL60PT cells caused the induction of resistance to 2.5 mMAs2O3. Conversely, forced expression of a dominant negative Akt in HL60AR cells resulted in a decrease in As2O3 resistance. Moreover, HL60 cell resistance to 2.5 mMAs2O3 could be significantly reduced by incubation with SN50, a peptide inhibitor selective for the NF-kB transcription factor. Taken together our findings suggest that a constitutive activation of the PI3K/Akt pathway, which is increasingly detected in some types of acute myeloid leukemia, may contribute to As2O3 resistance, most likely through NF-kB activation. Selective pharmacological inhibitors of this survival pathway, as well as of NF-kB, might be usefully employed in the future to reverse resistance to this treatment.nonemixedTABELLINI G; CAPPELLINI A; TAZZARI PL; FALA F; BILLI AM; MANZOLI L; COCCO L.; MARTELLI AM.TABELLINI G; CAPPELLINI A; TAZZARI PL; FALA F; BILLI AM; MANZOLI L; COCCO L.; MARTELLI AM

Phosphoinositide 3-kinase/Akt involvement in arsenic trioxide resistance of human leukemia cells

The purpose of this study was to evaluate the possible involvement of the phosphoinositide 3-kinase (PI3K)/Akt survival pathway in determining resistance to arsenic trioxide (As2O3)-induced apoptosis. We employed a HL60 cell clone (HL60AR) with a constitutively active PI3K/Akt survival pathway, as well as U937 and K562 cells. In addition, we used parental (PT) HL60 cells overexpressing a constitutively active Akt. Selective pharmacological inhibitors of the PI3K/Akt axis (LY294002, wortmannin) were employed to influence the sensitivity to As2O3. While HL60PT cells were sensitive to 2.5 mMAs2O3 and died of apoptosis, HL60AR cells were resistant up to 5 mM As2 O3. Treatment with either LY294002 or wortmannin lowered resistance of HL60AR cells to As2O3. Also in U937 and K562 cells, inhibitors of the PI3K/Akt axis caused a decrease in As2O3 resistance. Overexpression of constitutively active Akt in HL60PT cells caused the induction of resistance to 2.5 mMAs2O3. Conversely, forced expression of a dominant negative Akt in HL60AR cells resulted in a decrease in As2O3 resistance. Moreover, HL60 cell resistance to 2.5 mMAs2O3 could be significantly reduced by incubation with SN50, a peptide inhibitor selective for the NF-kB transcription factor. Taken together our findings suggest that a constitutive activation of the PI3K/Akt pathway, which is increasingly detected in some types of acute myeloid leukemia, may contribute to As2O3 resistance, most likely through NF-kB activation. Selective pharmacological inhibitors of this survival pathway, as well as of NF-kB, might be usefully employed in the future to reverse resistance to this treatment

Development of 2-(4-pyridyl)-benzimidazoles as PKN2 chemical tools to probe cancer

Kinases are signalling proteins which have proven to be successful targets for the treatment of a variety of diseases, predominantly in cancers. However, only a small proportion of kinases (<20%) have been investigated for their therapeutic viability, likely due to the lack of available chemical tools across the kinome. In this work we describe initial efforts in the development of a selective chemical tool for protein kinase N2 (PKN2), a relatively unexplored kinase of interest in several types of cancer. The most successful compound, 5, has a measured IC<sub>50</sub> of 0.064 μM against PKN2, with ca. 17-fold selectivity over close homologue, PKN1