Hypoxia-inducible factor 1-mediated human GATA1 induction promotes erythroid differentiation under hypoxic conditions

Hypoxia-inducible factor promotes erythropoiesis through coordinated cell type-specific hypoxia responses. GATA1 is essential to normal erythropoiesis and plays a crucial role in erythroid differentiation. In this study, we show that hypoxia-induced GATA1 expression is mediated by HIF1 in erythroid cells. Under hypoxic conditions, significantly increased GATA1 mRNA and protein levels were detected in K562 cells and erythroid induction cultures of CD34(+) haematopoietic stem/progenitor cells. Enforced HIF1α expression increased GATA1 expression, while HIF1α knockdown by RNA interference decreased GATA1 expression. In silico analysis revealed one potential hypoxia response element (HRE). The results from reporter gene and mutation analysis suggested that this element is necessary for hypoxic response. Chromatin immunoprecipitation (ChIP)-PCR showed that the putative HRE was recognized and bound by HIF1 in vivo. These results demonstrate that the up-regulation of GATA1 during hypoxia is directly mediated by HIF1.The mRNA expression of some erythroid differentiation markers was increased under hypoxic conditions, but decreased with RNA interference of HIF1α or GATA1. Flow cytometry analysis also indicated that hypoxia, desferrioxamine or CoCl(2) induced expression of erythroid surface markers CD71 and CD235a, while expression repression of HIF1α or GATA1 by RNA interference led to a decreased expression of CD235a. These results suggested that HIF1-mediated GATA1 up-regulation promotes erythropoiesis in order to satisfy the needs of an organism under hypoxic conditions.     

Tetramethylpyrazine inhibits CoCl2‐induced neurotoxicity through enhancement of Nrf2/GCLc/GSH and suppression of HIF1α/NOX2/ROS pathways

Hypoxia‐mediated neurotoxicity contributes to various neurodegenerative disorders, including Alzheimer's disease and multiple sclerosis. Tetramethylpyrazine (TMP), a major bioactive component purified from Ligusticum wallichii Franchat, exhibited potent neuroprotective effect. However, the mechanism of TMP‐exerted neuroprotective effect against hypoxia was not clear. In the study, we investigated the mechanism of the neuroprotective effect of TMP against hypoxia induced by CoCl₂ in vitro and in vivo. The results showed that TMP could protect against CoCl₂‐induced neurotoxicity in PC12 cells and in rats, as evidenced by enhancement of cell viability in PC12 cells and improvement of learning and memory ability in rats treated with CoCl₂. TMP could inhibit mitochondrial dysfunction, mitochondrial apoptotic molecular events, and thus apoptosis induced by CoCl₂. TMP inhibited CoCl₂‐increased reactive oxygen species (ROS) level, which may contribute to hypoxia‐related neurotoxicity induced by CoCl₂. The antioxidant and neuroprotective activities of TMP involved two pathways: one was the enhancement of nuclear factor erythroid 2‐related factor 2 (Nrf2)/catalytic subunit of γ‐glutamylcysteine ligase‐mediated regulation of GSH and the other was the inhibition of hypoxia‐inducible factor 1 α/NADPH oxidase 2 (NOX2)‐mediated ROS generation. These two pathways contributed to improvement of oxidative stress and thus the amelioration of apoptosis under hypoxic conditions. These results have appointed a new path toward the understanding of pathogenesis and TMP‐related therapy of hypoxia‐related neurodegenerative diseases.

     

Stretch-induced fetal type II cell differentiation is mediated via ErbB1-ErbB4 interactions

Stretch-induced differentiation of lung fetal type II epithelial cells is mediated through EGFR (ErbB1) via release of HB-EGF and TGF-α ligands. Employing an EGFR knock-out mice model, we further investigated the role of the ErbB family of receptors in mechanotranduction during lung development. Deletion of EGFR prevented endogenous and mechanical stretch-induced type II cell differentiation via the ERK pathway, which was rescued by overexpression of a constitutively active MEK. Interestingly, the expression of ErbB4, the only ErbB receptor that EGFR co-precipitates in wild-type cells, was decreased in EGFR-deficient type II cells. Similar to EGFR, ErbB4 was activated by stretch and participated in ERK phosphorylation and type II cell differentiation. However, neuregulin (NRG) or stretch-induced ErbB4 activation were blunted in EGFR-deficient cells and not rescued after ErbB4 overexpression, suggesting that induction of ErbB4 phosphorylation is EGFR-dependent. Finally, we addressed how shedding of ligands is regulated by EGFR. In knock-out cells, TGF-α, a ligand for EGFR, was not released by stretch, while HB-EGF, a ligand for EGFR and ErbB4, was shed by stretch although to a lower magnitude than in normal cells. Release of these ligands was inhibited by blocking EGFR and ERK pathway. In conclusion, our studies show that EGFR and ErbB4 regulate stretch-induced type II cell differentiation via ERK pathway. Interactions between these two receptors are important for mechanical signals in lung fetal type II cells. These studies provide novel insights into the cell signaling mechanisms regulating ErbB family receptors in lung cell differentiation.     

Recruitment of the Mint3 Adaptor Is Necessary for Export of the Amyloid Precursor Protein (APP) from the Golgi Complex

The amyloid precursor protein (APP) is a ubiquitously expressed single-pass transmembrane protein that undergoes proteolytic processing by secretases to generate the pathogenic amyloid-β peptide, the major component in Alzheimer plaques. The traffic of APP through the cell determines its exposure to secretases and consequently the cleavages that generate the pathogenic or nonpathogenic peptide fragments. Despite the likely importance of APP traffic to Alzheimer disease, we still lack clear models for the routing and regulation of APP in cells. Like the traffic of most transmembrane proteins, the binding of adaptors to its cytoplasmic tail, which is 47 residues long and contains at least four distinct sorting motifs, regulates that of APP. We tested each of these for effects on the traffic of APP from the Golgi by mutating key residues within them and examining adaptor recruitment at the Golgi and traffic to post-Golgi site(s). We demonstrate strict specificity for recruitment of the Mint3 adaptor by APP at the Golgi, a critical role for Tyr-682 (within the YENPTY motif) in Mint3 recruitment and export of APP from the Golgi, and we identify LAMP1⁺ structures as the proximal destination of APP after leaving the Golgi. Together, these data provide a detailed view of the first sorting step in its route to the cell surface and processing by secretases and further highlight the critical role played by Mint3.     

Immunogenic cell death,DAMPs and anticancer therapeutics: An emerging amalgamation

Immunogenic profile of certain cancer cell death mechanisms has been transmuted by research published over a period of last few years and this change has been so drastic that a new (sub)class of apoptotic cancer cell death, redefined as ‘immunogenic apoptosis’ has started taking shape. In fact, it has been shown that this chemotherapeutic agent-specific immunogenic cancer cell death modality has the capabilities to induce ‘anticancer vaccine effect’, in vivo. These new trends have given an opportunity to combine tumour cell kill and antitumour immunity within a single paradigm, a sort of ‘holy grail’ of anticancer therapeutics. At the molecular level, it has been shown that the immunological silhouette of these cell death pathways is defined by a set of molecules called ‘damage-associated molecular patterns (DAMPs)’. Various intracellular molecules like calreticulin (CRT), heat-shock proteins (HSPs), high-mobility group box-1 (HMGB1) protein, have been shown to be DAMPs exposed/secreted in a stress agent/factor-and cell death-specific manner. These discoveries have motivated further research into discovery of new DAMPs, new pathways for their exposure/secretion, search for new agents capable of inducing immunogenic cell death and urge to solve currently present problems with this paradigm. We anticipate that this emerging amalgamation of DAMPs, immunogenic cell death and anticancer therapeutics may be the key towards squelching cancer-related mortalities, in near future.     

The Reciprocal Regulation of γ-Synuclein and IGF-I Receptor Expression Creates a Circuit That Modulates IGF-I Signaling

Insulin-like growth factor (IGF) system plays important roles in carcinogenesis and maintenance of the malignant phenotype. Signaling through the IGF-I receptor (IGF-IR) has been shown to stimulate the growth and motility of a wide range of cancer cells. γ-Synuclein (SNCG) is primarily expressed in peripheral neurons but also overexpressed in various cancer cells. Overexpression of SNCG correlates with tumor progression. In the present study we demonstrated a reciprocal regulation of IGF-I signaling and SNCG expression. IGF-I induced SNCG expression in various cancer cells. IGF-IR knockdown or IGF-IR inhibitor repressed SNCG expression. Both phosphatidylinositol 3-kinase and mitogen-activated protein kinase were involved in IGF-I induction of SNCG expression. Interestingly, SNCG knockdown led to proteasomal degradation of IGF-IR, thereby decreasing the steady-state levels of IGF-IR. Silencing of SNCG resulted in a decrease in ligand-induced phosphorylation of IGF-IR and its downstream signaling components, including insulin receptor substrate (IRS), Akt, and ERK1/2. Strikingly, SNCG physically interacted with IGF-IR and IRS-2. Silencing of IRS-2 impaired the interaction between SNCG and IGF-IR. Finally, SNCG knockdown suppressed IGF-I-induced cell proliferation and migration. These data reveal that SNCG and IGF-IR are mutually regulated by each other. SNCG blockade may suppress IGF-I-induced cell proliferation and migration. Conversely, IGF-IR inhibitors may be of utility in suppressing the aberrant expression of SNCG in cancer cells and thereby block its pro-tumor effects.     

Geochemistry of Lake Biwa sediments revisited

Extensive chemical data for the Lake Biwa sediments were examined with statistical factor analysis to find any correlation patterns among elements and among samples. Based on those patterns, a series of x-y correlation plots of the concentrations of selected elements was constructed to see in detail how the concentrations of elements vary among different sample groups and explain the observed variation patterns.     

A Disintegrin and Metalloprotease 17 Dynamic Interaction Sequence,the Sweet Tooth for the Human Interleukin 6 Receptor

A disintegrin and metalloprotease 17 (ADAM17) is a major sheddase involved in the regulation of a wide range of biological processes. Key substrates of ADAM17 are the IL-6 receptor (IL-6R) and TNF-α. The extracellular region of ADAM17 consists of a prodomain, a catalytic domain, a disintegrin domain, and a membrane-proximal domain as well as a small stalk region. This study demonstrates that this juxtamembrane segment is highly conserved, α-helical, and involved in IL-6R binding. This process is regulated by the structure of the preceding membrane-proximal domain, which acts as molecular switch of ADAM17 activity operated by a protein-disulfide isomerase. Hence, we have termed the conserved stalk region “Conserved ADAM seventeen dynamic interaction sequence” (CANDIS). Finally, we identified the region in IL-6R that binds to CANDIS. In contrast to the type I transmembrane proteins, the IL-6R, and IL-1RII, CANDIS does not bind the type II transmembrane protein TNF-α, demonstrating fundamental differences in the respective shedding by ADAM17.