92 research outputs found
Role of phosphatidylinositol 5-phosphate 4-kinase α in zebrafish development
No full textPhosphatidylinositol 5-phosphate 4-kinases (PIP4Ks) phosphorylate phosphatidylinositol 5-phosphate (PI5P) to generate phosphatidylinositol 4,5-bisphosphate; their most likely function is the regulation of the levels of PI5P, a putative signalling intermediate. There are three mammalian PIP4Ks isoforms (α, β and γ), but their physiological roles remain poorly understood. In the present study, we identified the zebrafish orthologue (zPIP4Kα) of the high-activity human PIP4K α isoform and analyzed its role in embryonic development. RT-PCR analysis and whole-mount in situ hybridization experiments showed that zPIP4Kα is maternally expressed. At later embryonic stages, high PIP4Kα expression was detected in the head and the pectoral fins. Knockdown of zPIP4Kα by antisense morpholino oligonucleotides led to severe morphological abnormalities, including midbody winding defects at 48 hpf. The abnormal phenotype could be rescued, at least in large part, by injection of human PIP4Kα mRNA. Our results reveal a key role for PIP4Kα and its activity in vertebrate tissue homeostasis and organ development. © 2013 Elsevier Ltd
Essential Role of Type Iα Phosphatidylinositol 4-Phosphate 5-Kinase in Neurite Remodeling
No full textAbstractRapid neurite remodeling is fundamental to nervous system development and plasticity [1] and is regulated by Rho family GTPases that signal f-actin reorganization in response to various receptor ligands. Neuronal N1E-115 cells show dramatic neurite retraction and cell rounding in response to serum factors such as lysophosphatidic acid (LPA), sphingosine-1 phosphate (S1P), and thrombin, due to activation of the RhoA-Rho kinase pathway [2]. Type I phosphatidylinositol 4-phosphate 5-kinases (PIPkinase), which regulate cellular levels of PtdIns(4,5)P2[3], have been suggested as targets of the RhoA-Rho kinase pathway [4, 5] able to modulate cytoskeletal dynamics [6, 7]. Here, we show that the introduction of Type Iα PIPkinase into N1E-115 cells leads to cell rounding and complete inhibition of neurite outgrowth, perhaps through the dissociation of vinculin and the destabilization of focal adhesions. This occurs independently of RhoA, Rho kinase, and the activation of actomyosin contraction. Strikingly, expression of kinase-dead PIPkinase promotes the outgrowth of neurites, which fail to retract in response to LPA, S1P, thrombin, or active RhoA. Moreover, neurite retraction in response to an endogenous neuronal guidance cue, Semaphorin3A, was also dependent on Type Iα PIPkinase. Our results suggest an essential role for a Type I PIPkinase during neurite retraction in response to a number of diverse stimuli
Epidural analgesia versus patient-controlled analgesia for pain relief in uterine artery embolization for uterine fibroids: a decision analysis
No full textPurpose: This study was designed to compare the costs and effects of epidural analgesia (EDA) to those of patient-controlled intravenous analgesia (PCA) for postintervention pain relief in women having uterine artery embolization (UAE) for systematic uterine fibroids. Methods: Cost-effectiveness analysis (CEA) based on data from the literature by constructing a decision tree to model the clinical pathways for estimating the effects and costs of treatment with EDA and PCA. Literature on EDA for pain-relief after UAE was missing, and therefore, data on EDA for abdominal surgery were used. Outcome measures were compared costs to reduce one point in visual analogue score (VAS) or numeric rating scale (NRS) for pain 6 and 24 h after UAE and risk for complications. Results: Six hours after the intervention, the VAS was 3.56 when using PCA and 2.0 when using EDA. The costs for pain relief in women undergoing UAE with PCA and EDA were €191 and €355, respectively. The costs for EDA to reduce the VAS score 6 h after the intervention with one point compared with PCA were €105 and €179 after 24 h. The risk of having a complication was 2.45 times higher when using EDA. Conclusions: The results of this indirect comparison of EDA for abdominal surgery with PCA for UAE show that EDA would provide superior analgesia for post UAE pain at 6 and 24 h but with higher costs and an increased risk of complications.Sanne M. van der Kooij, Lobke M. Moolenaar, Willem M. Ankum, Jim A. Reekers, Ben Willem J. Mol, Wouter J. K. Hehenkam
Regulating c-Ras function cholesterol depletion affects caveolin association, GTP loading, and signaling
No full textAbstractCholesterol-rich and caveolin-containing microdomains of the plasma membrane, termed “caveolae,” have been implicated in signal transduction [1–4]. However, the role of caveolae in regulating the Ras-MAP kinase cascade is incompletely understood. The mammalian Ras isoforms (H, N, and K) use different membrane anchors to attach to the plasma membrane and thereby may localize to functionally distinct microdomains, which might explain isoform-specific signaling [5–9]. Here, we show that, in Cos epithelial cells, endogenous K-Ras colocalizes largely with caveolin, whereas N-Ras localizes to both caveolar and noncaveolar subdomains; H-Ras localization was below detection limits. We find that epidermal growth factor (EGF) activates N-Ras but fails to activate K-Ras in these cells. Extraction of cholesterol with methyl-β-cyclodextrin disrupts complex formation between caveolin and K- and N-Ras and, strikingy, enables EGF to activate both K-Ras and N-Ras. While cholesterol depletion enhances GTP-loading on total c-Ras, activation of the downstream MEK-MAP kinase cascade by EGF and lysophosphatidic acid but not that by phorbol ester is inhibited. Thus, plasma membrane cholesterol is essential for negative regulation of c-Ras isoforms (complexed to caveolin), as well as for mitogenic signaling downstream of receptor-activated c-Ras
Lysophospholipids in the limelight
No full textLysophosphatidic acid (LPA) is a serum phospholipid that evokes growth factor–like responses in many cell types through the activation of its G protein–coupled receptors. Although much is known about LPA signaling, it has remained unclear where and how bioactive LPA is produced. Umezu-Goto et al. (2002)(this issue, page 227) have purified a serum lysophospholipase D that generates LPA from lysophosphatidylcholine and found it to be identical to autotaxin, a cell motility–stimulating ectophosphodiesterase implicated in tumor progression. This result is surprising, as there was previously no indication that autotaxin could act as a phospholipase.</jats:p
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