Programmed cell death is a crucial process in the normal development and physiology of metazoans, and it can be divided into several categories that include type I death (apoptosis) and type II death ...(autophagic cell death). The Bcl-2 family proteins are well-characterized regulators of apoptosis, among which multidomain pro-apoptotic members (such as Bax and Bak) function as a mitochondrial gateway at which various apoptotic signals converge. Although embryonic fibroblasts from Bax/Bak double-knockout (DKO) mice are resistant to apoptosis, we have previously reported that these cells still die by autophagy in response to various death stimuli. In this study, we found that jun N-terminal kinase (JNK) was activated in etoposide- and staurosporine-treated, but not serum-starved, Bax/Bak DKO cells, and that autophagic cell death was suppressed by the addition of a JNK inhibitor and by a dominant-negative mutant of JNK. Studies with sek1(-/-)mkk7(-/-) cells revealed that disruption of JNK prevented the induction of autophagic cell death. Co-activation of JNK and autophagy induced autophagic cell death. Activation of JNK occurred downstream of the induction of autophagy, and was dependent on the autophagic process. These results indicate that JNK activation is crucial for the autophagic death of Bax/Bak DKO cells.
The mammalian Hippo pathway is composed of mammalian Ste20-like (MST) kinases and large tumour suppressor (LATS) kinases. Upon the activation of the pathway, MST kinases phosphorylate and activate ...LATS kinases, which in turn phosphorylate transcriptional co-activators, yes-associated protein (YAP) and transcriptional co-activator with PDZ-binding motif (TAZ), recruit them to the cytosol from the nucleus and turn off cell cycle-promoting and anti-apoptotic gene transcriptions. Thus, the pathway restricts cell overgrowth and prevents tumourigenesis. Although a high cell density and stress signallings are known to activate the pathway, no specific stimulators are so far reported. As the dysfunction of the pathway is frequent in human cancers and correlates with poor prognosis, it is important to find out reagents that stimulate the pathway for not only basic research but also clinical medicine. We here developed a cell-based method of screening reagents that induce the recruitment of YAP to the cytosol. Using this method, we found that dobutamine inhibits the YAP-dependent gene transcription. Contrary to our expectations, the effect of dobutamine is independent of the Hippo pathway but our method opens the possibility to discover Hippo pathway stimulators or Hippo-independent YAP inhibitors.
We have investigated the effects of moderate global undernutrition during gestation in the rat on the blood pressure of male
and female offspring, and on the development of systemic vascular ...function. Pregnant Wistar rats were nutritionally restricted
(R) by feeding with 70% of the normal gestation-matched dietary intake from 0 to 18 days gestation.
R offspring were growth retarded at birth but of similar weight to controls (C) at 20 days. Systolic and/or diastolic and
mean arterial blood pressures, measured directly by femoral artery catheter, were elevated from 60 days onward in male R offspring
(mean arterial pressure: day 60, P < 0.01; day 100, P < 0.05; day 200, P < 0.005, R vs. C), and from 100 days onward in female R offspring (mean arterial pressure day 100 and day 200, P < 0.05; R vs. C).
Maximal constriction to phenylephrine (PE) ( P < 0.05) and to noradrenaline (NA) ( P < 0.05) was reduced in isolated femoral arteries of day 20 R pups. These differences did not persist into adulthood. In male
adult R offspring (200 days), maximal vasoconstriction to the thromboxane A 2 mimetic, U46619 ( P < 0.05) and sensitivity to potassium ( P < 0.01) were enhanced.
Moderate maternal undernutrition in rat gestation adversely affects cardiovascular function in the offspring. These abnormalities
increase with age and are more pronounced in males.
Advances in stem cell biology have clarified that a tumour is a collection of heterogeneous cell populations, and that only a small fraction of tumour cells possesses the potential to self-renew. ...Delta-like 1 protein (Dlk-1) is a surface antigen present on foetal hepatic stem/progenitor cells but absent from mature hepatocytes in neonatal and adult rodent liver. Using a monoclonal antibody (mAb) against hDlk-1, Yanai et al. (Dlk-1, a cell surface antigen on foetal hepatic stem/progenitor cells, is expressed in hepatocellular, colon, pancreas and breast carcinomas at a high frequency. J. Biochem. 2010;148:85-92) have shown that human (h) Dlk-1 is expressed in human foetal, but not adult, liver and that 20% of all hepatocellular carcinomas (HCCs) are hDlk-1(+). Importantly, an even higher percentage of HCCs in younger patients are hDLK-1(+). These authors also found that hDlk-1 is present at high frequency in colon adenocarcinomas, pancreatic islet carcinomas and small cell lung carcinomas. Here, I discuss the implications of the expression of foetal hepatic stem/progenitor cell antigens on carcinoma cells.
Members of the Ras-association domain family (RASSF) of proteins influence apoptosis and cell cycling but little is known about the mechanisms. Here, we show that RASSF7 interacts with N-Ras and ...mitogen-activated protein kinase kinase 7 (MKK7) to negatively regulate c-Jun N-terminal kinase (JNK) signaling. Stress-induced JNK activation and apoptosis were markedly enhanced in cells depleted of RASSF7 or N-Ras by RNAi knockdown. An interaction with RASSF7 promoted the phosphorylated state of MKK7 but inhibited this kinase's ability to activate JNK. RASSF7 required its RA domain for both interaction with GTP-bound N-Ras and the anti-apoptotic response to stress stimuli. Following prolonged stress, however, RASSF7's anti-apoptotic effect was eliminated because of degradation of RASSF7 protein via the ubiquitin-proteasome pathway. Our results indicate that RASSF7 acts in concert with N-Ras to constitute a stress-sensitive temporary mechanism of apoptotic regulation. With initial stress, RASSF7/N-Ras promotes cell survival by inhibiting the MKK7/JNK pathway. However, with prolonged stress, RASSF7 protein undergoes degradation that allows cell death signaling to proceed. Our findings may account for the association of elevated RASSF7 with tumorigenesis.
Stress-activated protein kinase/c-Jun NH2-terminal kinase (SAPK/JNK) is activated by many types of cellular stresses and extracellular signals. Recent studies, including the analysis with knockout ...mice, have led to progress towards understanding the physiological roles of SAPK/JNK activation in embryonic development in addition to immune responses. SAPK/JNK activation plays essential roles in organogenesis during mouse development by regulating cell survival, apoptosis, and proliferation. Two SAPK/JNK activators, SEK1 and MKK7, are required for fetal liver formation and full activation of SAPK/JNK, which responds to various stimuli in an all-or-none manner. This article focuses on physiological roles of SAPK/JNK activation in fetal liver formation and in apoptosis regulation.
Mitogen-activated protein kinase kinases (MAPKKs) are important components of the stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) signalling pathway. Two MAPKKs that are crucial ...transducers upstream of JNK signalling are MKK4 and MKK7. These two MAPKKs directly phosphorylate specific Tyr and Thr residues located in the activation loop of the JNK protein and activate this kinase in response to environmental stress, pro-inflammatory cytokines or developmental cues. Although much is known about the biochemical and structural bases of the catalytic mechanism of the MAPKKs, the regulation and physiological functions of these enzymes during early embryogenesis have remained a mystery until relatively recently. Studies employing a range of animal models have now revealed the essential roles that MAPKKs play in diverse developmental contexts, including in dorsoventral patterning, convergent extension and somitogenesis. Focusing primarily on extensive work done in mouse and zebrafish models, this review summarizes the functional properties of MKK4 and MKK7 during vertebrate and invertebrate development, and the mechanisms by which these kinases regulate multiple steps in the establishment of the body plan of an organism.
During the development and organogenesis of all multicellular organisms, cell fate decisions determine whether cells undergo proliferation, differentiation, or aging. Two independent stress kinase ...signaling pathways, p38-MAPK, and JNKs, have evolved that relay developmental and environmental cues to determine cell responses. Although multiple stimuli can activate these two stress kinase pathways, the functional interactions and molecular cross-talks between these common second signaling cascades are poorly elucidated. Here we report that JNK and p38-MAPK pathways antagonistically control cellular senescence, oncogenic transformation, and proliferation in primary mouse embryonic fibroblasts (MEFs). Similarly, genetic inactivation of the JNK pathway results in impaired proliferation of fetal hepatoblasts in vitro and defective adult liver regeneration in vivo, which is rescued by inhibition of the p38-MAPK pathway. Thus, the balance between the two stress-signaling pathways, MKK7-JNK and MKK3/6-p38-MAPK, determines cell fate and links environmental and developmental stress to cell cycle arrest, senescence, oncogenic transformation, and adult tissue regeneration.
Abstract
The objectives of this study were to confirm the application of automatic system for detecting the water stress and the compatibility of the water stress treatment system for producing high ...soluble solids tomato fruits in high technology greenhouse. The tomato variety used, “Rinka 409”, was grown hydroponically with a high-wire system in high technology greenhouse in Faculty of Agriculture, Ehime University, Japan. The greenhouse has a full controlling system (temperature, relative humidity, carbon dioxide, and light intensity) to support the seasonal change and was adjusted to the real-time condition. Water stress condition of the tomato plant in the high technology greenhouse was detected by measuring the water content in the rockwool slab and by using visual monitoring system. The result showed that the automatically nutrient supplying system using visual monitoring system based on speaking plant approach technology could be used for the detection of water stress in the tomato plant. Using this system, water stress tomato cultivation was detected and the high soluble solids tomato fruits could be produced continuously to fulfill consumer expectation.
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