The JAK/STAT pathway was originally identified in mammals. Studies of this pathway in the mouse have revealed that JAK/STAT signaling plays a central role during hematopoeisis and other developmental processes. The role of JAK/STAT signaling in blood appears to be conserved throughout evolution, as it is also required during fly hematopoeisis. Studies in Dictyostelium, Drosophila, and zebrafish have shown that the JAK/STAT pathway is also required in an unusually broad set of developmental decisions, including cell proliferation, cell fate determination, cell migration, planar polarity, convergent extension, and immunity. There is increasing evidence that the versatility of this pathway relies on its cooperation with other signal transduction pathways. In this review, we discuss the components of the JAK/STAT pathway in model organisms and what is known about its requirement in cellular and developmental processes. In particular, we emphasize recent insights into the role that this pathway plays in the control of cell movement.

The JAK/STAT signal transduction pathway controls numerous events in Drosophila melanogaster development. Receptors for the pathway have yet to be identified. Here we have identified a Drosophila gene that shows embryonic mutant phenotypes identical to those in the hopscotch (hop)/JAK kinase and marelle (mrl)/Stat92e mutations. We named this gene master of marelle (mom). Genetic analyses place mom's function between upd (the ligand) and hop. We further show that cultured cells transfected with the mom gene bind UPD and activate the HOP/STAT92E signal transduction pathway. mom encodes a protein distantly related to the mammalian cytokine receptor family. These data show that mom functions as a receptor of the Drosophila JAK/STAT signal transduction pathway.

1. In an animal model in vivo, ginsenosides (GS), saponins from Panax ginseng, were shown to protect against myocardial ischaemia/reperfusion damage with concomitant increased 6-keto-PGF1 alpha and decreased lipid peroxidation. 2. In perfused rabbit lung in situ and isolated rabbit aortic rings, GS protected the pulmonary and aortic endothelium against electrolysis-induced free radical injury. Purified components of GS, Rb1 and especially Rg1, relaxed pulmonary vessels and this effect was eliminated by nitro-L-arginine, an inhibitor of nitric oxide (NO) synthase. 3. In cultured bovine aortic endothelial cells, GS enhanced the conversion of [14C]-L-arginine to [14C]-L-citrulline, indicating an increased release of NO. 4. As the neurotransmitter inducing penile erection, NO release was shown to be enhanced by GS in rabbit corpus cavernosum (CC) in vitro. Ginsenosides enhanced both acetylcholine-induced and transmural nerve stimulation-activated relaxation associated with increased tissue cGMP. The latter effect was eliminated by tetrodotoxin and was associated with decreased tissue cGMP. Ginsenoside-enhanced CC relaxation was attenuated by nitro-L-arginine and oxyhaemoglobin, and enhanced by superoxide dismutase. 5. It is postulated that cardiovascular protection by GS may be partly mediated by the release of NO, a potent antioxidant, and that the GS-enhanced release of NO from endothelial cells, especially from perivascular nitric oxidergic nerves in the CC, may partly account for the aphrodisiac effect of Panax ginseng used in traditional Chinese medicine.

Stem cells will undergo self-renewal to produce new stem cells if they are maintained in their niches. The regulatory mechanisms that recruit and maintain stem cells in their niches are not well understood. In Drosophila testes, a group of 12 nondividing somatic cells, called the hub, identifies the stem cell niche by producing the growth factor Unpaired (Upd). Here, we show that Rap-GEF/Rap signaling controls stem cell anchoring to the niche through regulating DE-cadherin-mediated cell adhesion. Loss of function of a Drosophila Rap-GEF (Gef26) results in loss of both germline and somatic stem cells. The Gef26 mutation specifically impairs adherens junctions at the hub-stem cell interface, which results in the stem cells "drifting away" from the niche and losing stem cell identity. Thus, the Rap signaling/E-cadherin pathway may represent one mechanism that regulates polarized niche formation and stem cell anchoring.

The Drosophila melanogaster JUN N-terminal kinase (DJNK) and DPP (decapentaplegic) signal transduction pathways coordinately regulate epithelial cell sheet movement during the process of dorsal closure in the embryo. By a genetic screen of mutations affecting dorsal closure in Drosophila, we have now identified a multidomain protein, connector of kinase to AP-1 (cka), that functions in the DJNK pathway and controls the localized expression of dpp in the leading-edge cells. We have also investigated how CKA acts. This unique molecule forms a complex with HEP (DJNKK), BSK (DJNK), DJUN, and DFOS. Complex formation activates BSK kinase, which in turn phosphorylates and activates DJUN and DFOS. These data suggest that CKA represents a novel molecule regulating AP-1 activity by organizing a molecular complex of kinases and transcription factors, thus coordinating the spatial-temporal expression of AP-1-regulated genes.Morphogenetic movements play a central role in the establishment of the overall body organization and shape during metazoan development. Most types of morphogenetic movements involve epithelial cell invagination and spreading (epiboly). In Drosophila melanogaster, the morphogenetic movement that occurs during dorsal closure (DC) of the embryonic epidermis has provided an excellent system for characterizing the molecular mechanisms underlying the coordinated movements of epithelial cell layers (8,13,25,26,38).DC is a major morphogenetic event that occurs during midembryogenesis. DC relies predominately on cell shape changes within the postmitotic epidermis. These changes are initiated in two symmetric dorsalmost rows of epidermal cells, known as the leading-edge (LE) cells, followed by the stretching of the more lateral epidermal cells, and are finished with the fusion of the two rows of LE cells at the dorsal midline (4,23,43).Embryos that fail to complete DC due to mutations in the genes required for this process die with a characteristic dorsalopen phenotype (14,27,29,41). Based on molecular data, two types of genes for DC have been identified. The first class identifies cytoskeletal and extracellular matrix components. These molecules may form the mechanical machinery that responds to signaling and drives cell shape changes. The second class identifies signaling molecules, including components in the D. melanogaster JUN N-terminal kinase (DJNK) signal transduction pathway and the dpp signal transduction pathway (8,13,25,26,38).Mutations in DJNK cascade genes block cell shape changes and disrupt organization of the cytoskeleton components at the LE. In addition, dpp gene expression is lost from the LE at the onset of DC. The Drosophila homologue of c -jun (Djun) is a central player in this signal transduction pathway (12,16,32). Djun mutations completely block epithelial cell sheet movement in DC. In doing so, DJUN is a target of the DJNK signal transduction pathway. DJNK may function by phosphorylating and activating DJUN, which in turn induces transcription of dpp in the LE cells during DC (12, 32). ...

1. In the present study, we tested the hypothesis that long-term administration of the hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor simvastatin may regress hypertrophy and the possible effect of simvastatin on angiotensin-converting enzyme (ACE) activity in rats with pressure-overload cardiac hypertrophy. 2. Pressure-overload left ventricular hypertrophy (LVH) of rats was induced by part coarctation of the abdominal aorta; a sham-operated group served as the control. Six weeks after operation, animals were divided into three groups and an 8 week treatment period was insitgated as follows: (i) the simvastatin treatment group received simvastatin at 3.6 mg/kg per day, p.o.; (ii) the ACE inhibitor group received captopril at 50 mg/kg per day, p.o.; and (iii) the LVH control group received no drug treatment. 3. At the end of the treatment period, left ventricular systolic pressure (LVSP) and left ventricular end-diastolic pressure (LVEDP) were monitored in vivo. Diastolic pressure-volume relationships were evaluated in a Langendorff preparation with a balloon-in-left ventricle (LV) heart. Myocyte cell width was measured. Angiotensin-converting enzyme activity and angiotensin (Ang)II and hydroxyproline contents of the LV were determined. 4. At the end of the experiments, LVH was established in the LVH control group by increases in LV weight, LV weight/body-weight ratio, LV weight/right ventricle weight ratio, LV myocyte cell width, LVSP and LVEDP by 40, 26, 19, 61, 56 and 59%, respectively (all P < 0.01), compared with the sham-operated group. In the simvastatin-treated and ACE inhibitor groups all these parameters were significantly reduced compared with sham-operated controls. In the LVH control group, ACE activity and AngII and hydroxyproline contents of LV tissue increased by 180, 123 and 70, respectively (all P < 0.01), compared with the sham-operated group. Compared with the LVH group, in the simvastatin-treated and ACE inhibitor groups ACE activity was reduced by 36 (P < 0.05) and 48% (P < 0.01), respectively, AngII content was reduced by 11 (P < 0.05) and 43% (P < 0.01), respectively, and hydroxyproline content was reduced by 23 (P < 0.01) and 10% (P < 0.05), respectively. 5. For the first time, the results of the present study demonstrate that simvastatin significantly reduces LVH, cardiac tissue ACE activity and improves LV performance in pressure-overloaded rats. Because, compared with captopril, simvastatin is more potent in its reduction of LVH and less potent in its inhibition of ACE activity, the mechanism of its antihypertrophic action, in addition to ACE inhibition, may involve inhibition of the mevalonic acid pathway, the main target of action of statins. Thus, HMG-CoA reductase inhibitors may be beneficial for the clinical treatment of cardiac hypertrophy.

Cardiovascular disease is the major cause of morbidity and mortality in Westernised societies. It is well known that the aetiology of this devastating disorder involves both genetic and environmental factors. Sequence variants of the components of the renin-angiotensin-aldosterone system and the kallikrein-kinin system are suggested to have significant influences on cardiovascular homeostasis. Both gene targeting and transgenic studies in mice have clearly suggested a critical role of the angiotensin converting enzyme (ACE) gene in blood pressure regulation. Furthermore, an up-regulation of myocardial ACE gene expression has been observed in patients with heart failure. Thus, the ACE gene has been recognised as a top candidate gene for cardiovascular research. Over the past decade, the insertion/deletion (I/D) polymorphism of a 287-bp Alu element in intron 16 of the ACE gene has attracted significant attention and has been extensively investigated in a spectrum of cardiovascular phenotypes, because of its correlation with serum ACE activity. A large majority of previous studies have shown a positive association between the DD genotype and an increased risk of myocardial infarction, but results in hypertension, left ventricular hypertrophy, cardiomyopathy and restenosis after percutaneous transluminal coronary angioplasty remain quite controversial. Since ACE inhibitors are widely used in hypertension and congestive heart failure, we also review the literature on the relationship of ACE I/D polymorphism with ACE inhibitor response. It appears that this polymorphism has some moderate impact on the cardiovascular response to ACE inhibitors but there is no consensus as to which allele confers a more pronounced effect. In addition, previous data are suggestive of an association between the ACE I allele and a greater risk of increased occurrence of ACE inhibitor-induced cough, but such a relationship needs further confirmation. Overall, since ACE I/D is only an intronic marker, the true locus that controls the ACE enzyme activity remains to be identified, and could be located within either the ACE gene or another nearby gene such as the human growth hormone gene. We note that since associations tend to vary across different gender or ethnic groups, or across different socio-ecological settings, consideration of potential gene-gene and gene-environment interactions should be made. Furthermore, the dissection of the genetic underpinning of cardiovascular disease needs delineation of all molecular variants of the key physiological pathways that influence cardiovascular function.

No abstract