1,721,526 research outputs found
ON SMOOTH AND ANALYTIC DISKS IN C-2 WITH COMMON BOUNDARY
No full textWe construct explicitly a real analytic embedded real two-dimensional disk in C-2 totally real except at exactly one elliptic complex tangent point, which shares the common boundary with an analytic disk in the same C-2, but does not contain this analytic disk in its envelope of holomorphy. The same proof further yields an explicit example of a holomorphic re-embedding of the standard two-sphere into C-2 in such a way that the new embedding shows some exceptional properties: It bounds a real three-dimensional Levi flat cell in C-2 foliated by analytic disks, which is not polynomially convex. In particular, this new embedding of the standard two-sphere cannot be a subset of any compact strongly pseudoconvex surface in C-2 or a subset of any strongly pseudoconvex graph in C-2 in the sense of Bedford and Gaveau.X110sci
On the automorphism groups of convex domains in C-n
No full textWe establish that every bounded convex domain in C-n with an automorphism orbit accumulation at a boundary point at which the domain has a sphere contact from inside admits a non-compact 1-parameter subgroup of automorphisms. Notice that this in particular implies that no Teichmuller domain of a Riemann surface of genus g > 1 can be holomorphically imbedded as a convex domain in C3g-3.X118sciescopu
Dominant role of lipid rafts L-type calcium channel in activity-dependent potentiation of large dense-core vesicle exocytosis
No full textCalcium influx triggers exocytosis by promoting vesicle fusion with the plasma membrane. However, different subtypes of voltage-gated calcium channel (VGCC) have distinct roles in exocytosis. We previously reported that repetitive stimulation induces activity-dependent potentiation (ADP) which represents the increase of neurotransmitter release. Here, we show that L-type VGCC have a dominant role in ADP of large dense-core vesicle (LDCV) exocytosis. Repetitive stimulation activating VGCC can induce ADP, whereas activation of bradykinin (BK) G protein-coupled receptors or purinergic P2X cation channels can not. L-type VGCC has the dominant role in ADP of LDCV exocytosis by regulating Protein Kinase C (PKC)-epsilon translocation and phosphorylation of myristoylated alanine-rich C kinase substrate (MARCKS), a target molecule of PKC-epsilon. We provide evidence that L-type VGCC, PKC-epsilon, and MARCKS, but not Q-type VGCC, are selectively located in lipid rafts. Also, PKC-epsilon translocation induced by L-type VGCC activation occurs in lipid rafts. Disruption of lipid rafts abolishes ADP of LDCV exocytosis and changes the fusion pore kinetics without affecting the first stimulation-induced exocytosis, showing that lipid rafts are involved in the potentiation process. Taken together, we suggest that L-type VGCC in lipid rafts selectively mediates ADP of LDCV exocytosis by regulating PKC-epsilon translocation and MARCKS phosphorylation.X1157sciescopu
Regulation of cyclin-dependent kinase 5 and p53 by ERK1/2 pathway in the DNA damage-induced neuronal death
No full textDNA damage is known to be an initiator of neuronal death in neurodegenerative conditions such as Parkinson's and Alzheimer's diseases. The mechanism linking DNA damage and neuronal death is not completely understood. Here, we delineate the mechanism by which neuronal death evoked by DNA damage is controlled. Using mouse cortical neurons and SH-SY5Y human neuroblastoma cells, we identify a critical role of ERK signaling in neuronal death induced by DNA damage upon mitomycin C treatment. In addition, we provide evidence that the ERK signaling regulates Cyclin-dependent kinase 5 (Cdk5) activity and stability of tumor suppressor p53. Mitomycin C increased expression of p35, a specific activator of neuronal Cdk5 in an ERK1/2-dependent manner. Moreover, stability of p53 was increased by its phosphorylation on Ser33 and Ser46 by Cdk5, leading to neuronal death. Finally, we show that activated ERK induced increased expression of the Egr-1 transcription factor, which then bound to the promoter region of p35. We suggest subsequent increase of p35 expression and Cdk5 activity contribute to p53-dependent neuronal death. Thus, the present finding provides a new insight into a molecular mechanism underlying DNA damage-induced neuronal death.X113133sciescopu
VRK3-mediated inactivation of ERK signaling in adult and embryonic rodent tissues
No full textVaccinia-related kinase 3 (VRK3), previously characterized as a direct activator of vaccinia HI-related (VHR) phosphatase, inactivates extracellular signal-regulated kinase (ERK) in the nucleus of neuronal cells. Here we show that VRK3 is expressed in various other rodent tissues and in embryos, and regulates VHR phosphatase activity in these tissues. We observed colocalization of VRK3 and VHR in the testis tissue and could detect protein complex containing VRK3, VHR and ERK in immunoprecipitation analysis. Notably, the addition of recombinant VRK3 protein to total protein lysates, obtained either from adult tissues or embryos, enhanced the phosphatase activity of VHR, but not the activity of MKP3. The results further indicate that the VHR-VRK3 complex is a phosphatase-active form. In addition, we found that VRK3 can regulate EGF-induced cellular growth signaling that is mediated by ERK activation. Our results suggest that in addition to neuronal cells, various other rodent adult tissues and embryos possess a common signaling mechanism which is involved in an indirect regulation of ERK activity by VRK3-mediated VHR activity. (C) 2007 Elsevier B.V. All rights reserved.X111313sciescopu
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