Home About us Contact
|
Home About us Contact | ||
|
|
||
PKA Activation (pka + activation)
Selected AbstractsLocal activation of protein kinase A inhibits morphogenetic movements during Xenopus gastrulationDEVELOPMENTAL DYNAMICS, Issue 1 2003Byung-Ho Song Abstract cAMP-dependent protein kinase (PKA) has various biological roles in many organisms. However, little is known about its role in the developmental processes of vertebrates. In this study, we describe the functional analysis of PKA during gastrulation movements in Xenopus laevis. Overexpression of constitutively active PKA (cPKA) in the dorsal equatorial region of the embryo affects morphogenetic movement during gastrulation. We also show that intrinsic differences of PKA activities along the dorsoventral axis are set up and the level of PKA activity on the dorsal region is lower than that on the ventral region from late blastula to gastrula stages. In addition, PKA activation in animal explants inhibits activin-induced elongation. In cPKA-injected embryos, there were no changes in the expressions of markers involved in mesoderm specification, although the correct expression domains of these genes were altered. The effects of PKA activation can be restored by coexpression of PKI, a pseudosubstrate of PKA. We further analyzed the effects of PKA activation on the behavior of migratory gastrulating cells in vitro. Expression of cPKA in head mesoderm cells causes less polarized and/or randomized migration as demonstrated by a directional cell migration assay. Finally, we show that RhoA GTPase lies downstream of PKA, affecting activin-induced convergent extension movements. Taken together, these results suggest that overexpressed PKA can modulate a pathway responsible for morphogenetic movements during Xenopus gastrulation. Developmental Dynamics 227:91,103, 2003. © 2003 Wiley-Liss, Inc. [source] Activation of ERK signaling upon alternative protease nexin-1 internalization mediated by syndecan-1JOURNAL OF CELLULAR BIOCHEMISTRY, Issue 3 2006Xiaobiao Li Abstract Protease nexin-1 (PN-1), an inhibitor of serine proteases, contributes to tissue homeostasis and influences the behavior of some tumor cells. The internalization of PN-1 protease complexes is considered to be mediated by the low-density lipoprotein receptor related protein 1 (LRP1). In this study, both wild-type and LRP1,/, mouse embryonic fibroblasts (MEF) were shown to internalize PN-1. Receptor associated protein (RAP) interfered with PN-1 uptake only in wild-type MEF cells, indicating that another receptor mediates PN-1 uptake in the absence of LRP1. In LRP1,/, MEF cells, inhibitor sensitivity and kinetic values (t1/2 at 45 min) of PN-1 uptake showed a similarity to syndecan-1-mediated endocytosis. In these cells, PN-1 uptake was increased by overexpression of full-length syndecan-1 and decreased by RNA interference targeting this proteoglycan. Most important, in contrast to PKA activation known to be triggered by LRP1-mediated internalization, our study shows that syndecan-1-mediated internalization of PN-1 stimulated the Ras-ERK signaling pathway. J. Cell. Biochem. 99: 936,951, 2006. © 2006 Wiley-Liss, Inc. [source] Depolarization recruits DCC to the plasma membrane of embryonic cortical neurons and enhances axon extension in response to netrin-1JOURNAL OF NEUROCHEMISTRY, Issue 2 2008Jean-François Bouchard Abstract The netrin-1 receptor Deleted in Colorectal Cancer (DCC) is required for the formation of major axonal projections by embryonic cortical neurons, including the corpus callosum, hippocampal commissure, and cortico-thalamic tracts. The presentation of DCC by axonal growth cones is tightly regulated, but the mechanisms regulating DCC trafficking within neurons are not well understood. Here, we investigated the mechanisms regulating DCC recruitment to the plasma membrane of embryonic cortical neurons. In embryonic spinal commissural neurons, protein kinase A (PKA) activation recruits DCC to the plasma membrane and enhances axon chemoattraction to netrin-1. We demonstrate that PKA activation similarly recruits DCC and increases embryonic cortical neuron axon extension, which, like spinal commissural neurons, respond to netrin-1 as a chemoattractant. We then determined if depolarization might recruit DCC to the plasma membrane. Neither netrin-1 induced axon extension, nor levels of plasma membrane DCC, were altered by depolarizing embryonic spinal commissural neurons with elevated levels of KCl. In contrast, depolarizing embryonic cortical neurons increased the amount of plasma membrane DCC, including at the growth cone, and increased axon outgrowth evoked by netrin-1. Inhibition of PKA, phosphatidylinositol-3-kinase, protein kinase C, or exocytosis blocked the depolarization-induced recruitment of DCC and suppressed axon outgrowth. Inhibiting protein synthesis did not affect DCC recruitment, nor were the distributions of trkB or neural cell adhesion molecule (NCAM) influenced by depolarization, consistent with selective mobilization of DCC. These findings identify a role for membrane depolarization modulating the response of axons to netrin-1 by regulating DCC recruitment to the plasma membrane. [source] Inter-relationship of cytokine production and NOS2 expression in microgliaJOURNAL OF NEUROCHEMISTRY, Issue 2002C. Dello Russo Under normal conditions, glial cells provide neurotrophic support, but can contribute to damage during neurodegenerative disorders such as multiple sclerosis and Alzheimer's disease. Once activated, glia produce and release inflammatory mediators and potentially neurotoxic substances (including cytokines, NO, and prostanoids) whose interactions could lead to sustained inflammation. We investigated the relationship between cytokine production and NO release using enriched cultures of rat microglia. Preliminary data suggest that low concentrations of endotoxin LPS (1,10 ng/mL) activated microglia by a complex mechanism involving NF,B activation, cAMP increase and PKA activation, and IL-1, production and release. We characterized this system using pharmacological activators and inhibitors of NF,B and PKA, and IL-1r, to reduce IL-1, effects. Norepinephrine (NE) dose-dependently inhibited LPS-induced NOS2 expression and NO generation, via activation of ,-2 adrenergic receptors (,2-ARs) and elevation of cAMP. Similarly, NE dose-dependently blocked LPS-dependent IL-1, production. The addition of PKA inhibitors did not reverse the suppressive effects of NE on NO production, but did reverse its effects on IL-1,. Addition of IL-1r, also reduced NO production, and exogenous IL-1, reversed the inhibitory effects of NE. These data suggest that effects of NE on LPS-dependent NO release is, at least in part, mediated by blocking of IL-1, secretion. At the same time, results with inhibitors suggest that PKA activation is necessary for LPS effects. Together, these results point to the existence of autocrine and paracrine regulatory mechanisms of microglia activation. The relationship between cytokines and NO could be an important mechanism of sustained and disruptive microglia activation. [source] Pituitary adenylate cyclase-activating polypeptide regulates forebrain neural stem cells and neurogenesis in vitro and in vivoJOURNAL OF NEUROSCIENCE RESEARCH, Issue 6 2006Shigeki Ohta Abstract Recent studies suggest that adult neurogenesis can contribute significantly to recovery from brain damage. As a result, there is strong interest in the field in identifying potentially therapeutic factors capable of promoting increased expansion of endogenous neural stem cell (NSC) populations and increased neurogenesis. In the present study, we have investigated the effects of PACAP on the NSC populations of the embryonic and adult forebrain. Our results demonstrate that the PACAP receptor, PAC1-R, is expressed by both embryonic and adult NSCs. The activation of PACAP signaling in vitro enhanced NSC proliferation/survival through a protein kinase A (PKA)-independent mechanism. In contrast, PACAP promoted NSC self-renewal and neurogenesis through a mechanism dependent on PKA activation. Finally, we determined that the intracerebroventricular infusion of PACAP into the adult forebrain was sufficient to increase neurogenesis significantly in both the hippocampus and the subventricular zone. These results demonstrate PACAP is unique in that it is capable of promoting NSC proliferation/survival, self-renewal, and neurogenesis and, therefore, may be ideal for promoting the endogenous regeneration of damaged brain tissue. © 2006 Wiley-Liss, Inc. [source] Protein kinase C mediates up-regulation of tetrodotoxin-resistant, persistent Na+ current in rat and mouse sensory neuronesTHE JOURNAL OF PHYSIOLOGY, Issue 3 2005Mark D. Baker The tetrodotoxin-resistant (TTX-r) persistent Na+ current, attributed to NaV1.9, was recorded in small (< 25 ,m apparent diameter) dorsal root ganglion (DRG) neurones cultured from P21 rats and from adult wild-type and NaV1.8 null mice. In conventional whole-cell recordings intracellular GTP-,-S caused current up-regulation, an effect inhibited by the PKC pseudosubstrate inhibitor, PKC19,36. The current amplitude was also up-regulated by 25 ,m intracellular 1-oleoyl-2-acetyl-sn-glycerol (OAG) consistent with PKC involvement. In perforated-patch recordings, phorbol 12-myristate 13-acetate (PMA) up-regulated the current, whereas membrane-permeant activators of protein kinase A (PKA) were without effect. PGE2 did not acutely up-regulate the current. Conversely, both PGE2 and PKA activation up-regulated the major TTX-r Na+ current, NaV1.8. Extracellular ATP up-regulated the persistent current with an average apparent Kd near 13 ,m, possibly consistent with P2Y receptor activation. Numerical simulation of the up-regulation qualitatively reproduced changes in sensory neurone firing properties. The activation of PKC appears to be a necessary step in the GTP-dependent up-regulation of persistent Na+ current. [source] Inhibition of cAMP-dependent protein kinase A: a novel cyclo-oxygenase-independent effect of non-steroidal anti-inflammatory drugs in adipocytesAUTONOMIC & AUTACOID PHARMACOLOGY, Issue 2 2007M. Zentella de Piña Summary 1 Non-steroidal anti-inflammatory drugs (NSAIDs) [acetylsalicylic acid (ASS), naproxen, nimesulide and piroxicam] decreased adrenaline- or dibutyryl cAMP-stimulated glycerol release in isolated adipocytes. We aimed to determine the mechanism of this NSAIDs action. 2 Non-steroidal anti-inflammatory drugs decreased cAMP-dependent protein kinase A (PKA) activity in rat adipocyte lysates and in a commercial bovine heart PKA holoenzyme. If added before cAMP, NSAIDs impaired PKA activation by the cyclic nucleotide; however, if PKA was first activated by cAMP, NSAIDs were ineffective. NSAIDs were also ineffective against PKA catalytic subunits. 3 Consequently, NSAIDs lowered hormone-sensitive lipase translocation from cytosol to lipid storage droplets in adipocytes lysates, the critical event to promote lipolysis. 4 These results indicate that inhibition of PKA activation explains NSAIDs-induced decrease in adrenaline-stimulated lipolysis. We suggest that reproduction of such inhibition in nociceptive cells might enhance the understanding of the mechanism underlying the analgesic effects of NSAIDs. [source] | ||||||||||