Biology subjects

Mustafa, A.-H. M.

Publications and source records attributed to Mustafa, A.-H. M..

3 recordsLinked to original sources

bioRxiv2023

The protein phosphatase-2A subunit PR130 is linked to cytotoxic protein aggregate formation in mesenchymal pancreatic ductal adenocarcinoma cells

Protein phosphatase-2A (PP2A) is a major source of cellular serine/threonine phosphatase activity. PP2A B-type subunits regulate the intracellular localization and the catalytic activity of PP2A-A/PP2A-C complexes towards individual proteins. There is limited knowledge on how PP2A B-type subunits regulate biologically important functions and if these subunits determine the growth and drug responsiveness of tumor cells. Pancreatic ductal adenocarcinoma (PDAC) is a dismal disease with poor prognosis. Mesenchymal PDAC subtypes are more aggressive and metastasis-prone than epithelial subtypes. We show that mesenchymal PDAC cells express significantly higher levels of the PP2A B-type subunit PR130 and its mRNA Ppp2r3a than epithelial PDAC cells (n=38). Among 17 PP2A B-type subunits, this differential regulation is unique for Ppp2r3a and PR130. The higher levels of PR130 in mesenchymal PDAC cells are linked to their vulnerability to the PP2A inhibitor phendione. Phendione induces apoptosis and an accumulation of cytotoxic protein aggregates in such cells. These processes occur independently of the major tumor suppressor p53, which is frequently mutated in PDAC cells. Proteomic analyses reveal that phendione upregulates the chaperone heat shock protein HSP70 in mesenchymal PDAC cells. Inhibition of HSP70 promotes phendione-induced apoptosis. We additionally disclose that phendione promotes a proteasomal degradation of PR130. Genetic elimination of PR130 sensitizes mesenchymal PDAC cells to phendione-induced apoptosis and protein aggregate formation. These data illustrate pharmacologically amenable, selective dependencies of mesenchymal PDAC cells on PP2A-PR130 and HSP70. PP2A inhibition triggers a harmful accumulation of protein aggregates in neurons. This undesired mechanism might be exploited to kill mesenchymal tumor cells. O_FIG O_LINKSMALLFIG WIDTH=137 HEIGHT=200 SRC="FIGDIR/small/556106v1_ufig1.gif" ALT="Figure 1"> View larger version (40K): org.highwire.dtl.DTLVardef@c8a47forg.highwire.dtl.DTLVardef@a7abfforg.highwire.dtl.DTLVardef@d18a3org.highwire.dtl.DTLVardef@1cc9943_HPS_FORMAT_FIGEXP M_FIG C_FIG HIGHLIGHTS[tpltrtarr] The PP2A subunit PR130 is a molecular marker of mesenchymal PDAC cells [tpltrtarr]The small molecule PP2A inhibitor phendione selectively kills mesenchymal PDAC cells [tpltrtarr]Phendione decreases PR130 through proteasomes and selectively increases the heat shock protein 70 kDa in mesenchymal PDAC cells [tpltrtarr]HSP70 promotes cell survival upon inhibition of PP2A [tpltrtarr]PP2A-PR130 regulates the accumulation of cytotoxic protein aggregates in mesenchymal PDAC cells

cancer biology↗

bioRxiv2023

Novel hydroxamic acid derivative induces apoptosis and constrains autophagy in leukemic cells

IntroductionPosttranslational modification of proteins by reversible acetylation regulates key biological processes. Histone deacetylases (HDACs) catalyze protein deacetylation and are frequently dysregulated in tumors. This has spurred the development of HDAC inhibitors (HDACi). Such epigenetic drugs modulate protein acetylation, eliminate tumor cells, and are approved for the treatment of blood cancers. ObjectivesWe aimed to identify novel, nanomolar HDACi with increased potency over existing agents and selectivity for the cancer-relevant class I HDACs (HDAC1/-2/-3/-8). Moreover, we wanted to define how such drugs control the apoptosis-autophagy interplay. As test systems, we used human leukemic cells and embryonic kidney-derived cells. MethodsWe synthesized novel pyrimidine-hydroxamic acid HDACi (KH9/KH16/KH29) and performed in vitro activity assays and molecular modeling of their direct binding to HDACs. We analyzed how these HDACi affect leukemic cell fate, acetylation, and protein expression with flow cytometry and immunoblot. The publicly available DepMap database of CRISPR-Cas9 screenings was used to determine sensitivity factors across human leukemic cells. ResultsNovel HDACi show nanomolar activity against class I HDACs. These agents are superior to the clinically used hydroxamic acid HDACi vorinostat. Within the KH-series of compounds, KH16 (yanostat) is the most effective inhibitor of HDAC3 (IC50 = 6 nM) and the most potent inducer of apoptosis (IC50 = 110 nM; p<0.0001) in leukemic cells. KH16 though spares embryonic kidney-derived cells. Global data analyses of knockout screenings verify that HDAC3 is a dependency factor in human blood cancer cells of different lineages, independent of mutations in the tumor suppressor p53. KH16 alters pro- and anti-apoptotic protein expression, stalls cell cycle progression, and induces a caspase-dependent processing of the autophagy proteins ULK1 and p62. ConclusionThese data reveal that HDACs are required to stabilize autophagy proteins through a suppression of apoptosis in leukemic cells. HDAC3 appears as a valid anti-cancer target for pharmacological intervention. HighlightsO_LINovel HDACi with nanomolar activity against leukemic cells were synthesized. C_LIO_LIHDACi of the KH-series are superior to a clinical grade HDACi. C_LIO_LIHDACi of the KH-series modulate acetylation and phosphorylation of proteins. C_LIO_LIThe new HDACi KH16 regulates cell cycle arrest, apoptosis, and autophagy. C_LIO_LIApoptosis acts upstream of autophagy in KH16-treated cells. C_LI

pharmacology and toxicology↗

bioRxiv2020

Structural insights into the interaction of heme with protein tyrosine kinase JAK2

Janus kinase 2 (JAK2) is the most important signal transducing tyrosine kinase in erythropoietic precursor cells. Its malfunction drives several myeloproliferative disorders. Heme is a small metal ion-carrying molecule, which is incorporated into hemoglobin in erythroid precursor cells to transport oxygen. In addition, heme is a signaling molecule and regulator of various biochemical processes. Here we show that heme exposure leads to hyperphosphorylation of JAK2 in a myeloid cancer cell line. Two peptides identified in JAK2 represent heme-regulatory motifs and show low micromolar affinities for heme. These peptides map to the kinase domain of JAK2, which is essential for downstream signaling. We suggest these motifs to be the interaction sites of heme with JAK2, which drive the heme-induced hyperphosphorylation. The results presented herein may facilitate the development of heme-related pharmacological tools to combat myeloproliferative disorders.

biochemistry↗