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Complement C3Complement C4Complement C4aComplement C3aComplement C1qComplement C5aComplement ActivationComplement C4bComplement C5Complement C3bComplement System ProteinsComplement C6Complement C3cComplement C3dComplement C2Complement C9Receptors, ComplementComplement C1sComplement Membrane Attack ComplexComplement C1rComplement Inactivator ProteinsComplement C7Complement C3-C5 ConvertasesComplement Factor BComplement Pathway, AlternativeComplement Pathway, ClassicalComplement C8Complement C1Receptors, Complement 3bComplement Factor HComplement C5bComplement C2aReceptor, Anaphylatoxin C5aComplement Activating EnzymesComplement Inactivating AgentsComplement Hemolytic Activity AssayComplement C1 Inactivator ProteinsReceptors, Complement 3dAnaphylatoxinsComplement Fixation TestsComplement Factor DComplement Factor IComplement C4b-Binding ProteinComplement C3b Inactivator ProteinsAntigens, CD55Complement C3-C5 Convertases, Classical PathwayComplement C2bAntigens, CD59Cobra VenomsAntigen-Antibody ComplexSteroid 21-HydroxylaseComplement C3-C5 Convertases, Alternative PathwayComplement C1 Inhibitor ProteinImmunoglobulin GHemolysisComplement C3 Convertase, Alternative PathwayComplement C5 Convertase, Classical PathwayMolecular Sequence DataComplement C3 Convertase, Classical PathwayAntigens, CD46Opsonin ProteinsBlood ProteinsLupus Erythematosus, SystemicComplement C5 Convertase, Alternative PathwayPhagocytosisAmino Acid SequenceComplement Pathway, Mannose-Binding LectinProperdinComplement C5a, des-ArginineMice, Inbred C57BLMacrophage-1 AntigenProtein BindingNeutrophilsBase SequenceKidney GlomerulusSerumGlomerulonephritis, MembranoproliferativeImmunoglobulin MSchistosomaGenetic Complementation TestEnzyme-Linked Immunosorbent AssayMice, KnockoutGlomerulonephritisArteriolosclerosisAntibodies, MonoclonalMajor Histocompatibility ComplexErythrocytesAutoantibodiesCells, CulturedRNA, MessengerMacrophagesCell LineImmunity, InnatePeptide FragmentsMutationRabbitsDisease Models, AnimalCloning, MolecularMice, Inbred BALB CBinding Sites

Nuclear phosphoinositide 3-kinase C2beta activation during G2/M phase of the cell cycle in HL-60 cells. (1/5)

The activity of nuclear phosphoinositide 3-kinase C2beta (PI3K-C2beta) was investigated in HL-60 cells blocked by aphidicolin at G(1)/S boundary and allowed to progress synchronously through the cell cycle. The activity of immunoprecipitated PI3K-C2beta in the nuclei and nuclear envelopes showed peak activity at 8 h after release from the G(1)/S block, which correlates with G(2)/M phase of the cell cycle. In the nuclei and nuclear envelopes isolated from HL-60 cells at 8 h after release from G(1)/S block, a significant increase in the level of incorporation of radiolabeled phosphate into phosphatidylinositol 3-phosphate (PtdIns(3)P) was observed with no change in the level of radiolabeled PtdIns(4)P, PtdIns(4,5)P(2) and PtdIns(3,4,5)P(3). On Western blots, PI3K-C2beta revealed a single immunoreactive band of 180 kDa, whereas in the nuclei and nuclear envelopes isolated at 8 h after release, the gel shift of 18 kDa was observed. When nuclear envelopes were treated for 20 min with mu-calpain in vitro, the similar gel shift and increase in PI3K-C2beta activity was observed which was completely inhibited by pretreatment with calpain inhibitor calpeptin. The presence of PI3K inhibitor LY 294002 completely abolished the calpain-mediated increase in the activity of PI3K-C2beta but did not prevent the gel shift. When HL-60 cells were released from G(1)/S block in the presence of either calpeptin or LY 294002, the activation of nuclear PI3K-C2beta was completely inhibited. These results demonstrate the calpain-mediated activation of the nuclear PI3K-C2beta during G(2)/M phase of the cell cycle in HL-60 cells.  (+info)

The structure of C2b, a fragment of complement component C2 produced during C3 convertase formation. (2/5)

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Postsynaptic regulation of synaptic plasticity by synaptotagmin 4 requires both C2 domains. (3/5)

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Effect of sodium chloride concentration on fluid-phase assembly and stability of the C3 convertase of the classical pathway of the complement system. (4/5)

The assembly of the classical-pathway C3 convertase from C4 and I2-treated C2 by the action of C1s is an Mg2(+)-dependent reaction. The Mg2+ concentration necessary for the assembly of C3 convertase in the fluid phase was found to be dependent on NaCl concentration. In the absence of NaCl more than 5 mM-MgCl2 was found to be required, whereas 0.5 mM-MgCl2 was adequate for the assembly of C3 convertase in the presence of 150 mM-NaCl. The C3 convertase assembled in a low-ionic-strength buffer was extremely labile compared with that assembled in buffer of physiological ionic strength, and the stability of C3 convertase was improved with the increase in NaCl concentration. It was found that the stabilizing effect of NaCl on C3 convertase was due to inhibition of the dissociating activity of C2b, which was formed during the assembly of C3 convertase. In addition to the dissociation-accelerating effect, C2b inhibited the assembly of C3 convertase in low-ionic-strength buffer, and this effect also was diminished with increase in NaCl concentration. An increase in NaCl concentration to more than 200 mM resulted in a decrease in the assembly of C3 convertase. This effect was not due to the lability of the assembled C3 convertase but due rather to the inhibition of C2 cleavage by C1s. Purified C3 convertase itself is stable in dilute medium or high-ionic-strength medium such as 500 mM-NaCl, suggesting that the interactions between C4b and C2a are hydrophobic. In these respects C2b seemed to be functionally similar to C4bp, but C2b failed to act as a cofactor for the Factor I-catalysed C4b cleavage.  (+info)

Purification and characterization of the C3 convertase of the classical pathway of human complement system by size exclusion high-performance liquid chromatography. (5/5)

The C3 convertase of the classical pathway of the complement system is a liable complex, C4b,2a, and is activated by limited proteolysis of two components, C4 and C2, by C1s. By utilizing iodine-treated C2 and size exclusion high-performance liquid chromatography (HPLC), we have succeeded in isolating for the first time the classical pathway C3 convertase. Size exclusion HPLC demonstrated that the apparent molecular mass of the C3 convertase was 280K daltons. The C3 convertase decay-dissociates spontaneously into C4b and C2a. The decay-dissociation is a temperature-dependent reaction and the half-lives of the C3 convertase at 24, 30, and 37 degrees C were estimated to be 400, 180, and 60 min, respectively. The decay-dissociation was also dependent on pH and was accelerated by increasing pH. In addition, the decay-dissociation of the C3 convertase was accelerated by C2b. This result suggests that C2b acts as a feedback inhibitor on the activation of the classical pathway of complement system.  (+info)