scholarly journals Characterization of preptin-induced insulin secretion in pancreatic β-cells

2012 ◽  
Vol 215 (1) ◽  
pp. 43-49 ◽  
Author(s):  
Kai-Chun Cheng ◽  
Ying-Xiao Li ◽  
Akihiro Asakawa ◽  
Miharu Ushikai ◽  
Ikuo Kato ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Cellular Level ◽  
Dependent Manner ◽  
Acetoxymethyl Ester ◽  
Concentration Dependent Manner ◽  
Kinase C ◽  
Intracellular Ca ◽  
Dose Dependent ◽  
Pkc Activation

We aimed to characterize the effects of preptin on insulin secretion at the single-cell level, as well as the mechanisms underlying these changes, with respect to regulation by intracellular Ca2+[Ca2+]imobilization. This study assessed the effect of preptin on insulin secretion and investigated the link between preptin and the phospholipase C (PLC)/protein kinase C (PKC) pathway at the cellular level using fura-2 pentakis(acetoxymethyl) ester-loaded insulin-producing cells (Min 6 cells). Our results demonstrate that preptin promotes insulin secretion in a concentration-dependent manner. Using a PLC inhibitor (chelerythrine) or a PKC inhibitor (U73122) resulted in a concentration-dependent decrease in insulin secretion. Also, preptin mixed with IGF2 receptor (IGF2R) antibodies suppressed insulin secretion in a dose-dependent manner, which indicates that activation of IGF2R is mediated probably because preptin is a type of proIGF2. In addition, preptin stimulated insulin secretion to a similar level as did glibenclamide. The activation of PKC/PLC by preptin stimulation is highly relevant to the potential mechanisms for increase in insulin secretion. Our results provide new insight into the insulin secretion of preptin, a secreted proIGF2-derived peptide that can induce greater efficacy of signal transduction resulting from PLC and PKC activation through the IGF2R.

Low [Mg2+]o induces contraction and [Ca2+]i rises in cerebral arteries: roles of Ca2+, PKC, and PI3

2000 ◽  
Vol 279 (6) ◽  
pp. H2898-H2907 ◽  
Author(s):  
Zhi-Wei Yang ◽  
Jun Wang ◽  
Tao Zheng ◽  
Bella T. Altura ◽  
Burton M. Altura
Keyword(s):  
Cerebral Arteries ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Voltage Gated ◽  
Selective Antagonist ◽  
Kinase C ◽  
Pkc Isoforms ◽  
Intracellular Ca ◽  
Basilar Arteries ◽  
Specific Antagonist

Removal of extracellular Ca2+ concentration ([Ca2+]o) and pretreatment of canine basilar arterial rings with either an antagonist of voltage-gated Ca2+ channels (verapamil), a selective antagonist of the sarcoplasmic reticulum Ca2+ pump [thapsigargin (TSG)], caffeine plus a specific antagonist of ryanodine-sensitive Ca2+ release (ryanodine), or ad- myo-inositol 1,4,5-trisphosphate [Ins(1,4,5)P3]- mediated Ca2+ release antagonist (heparin) markedly attenuates low extracellular Mg2+ concentration ([Mg2+]o)-induced contractions. Low [Mg2+]o-induced contractions are significantly inhibited by pretreatment of the vessels with Gö-6976 [a protein kinase C-α (PKC-α)- and PKC-βI-selective antagonist], bisindolylmaleimide I (Bis, a specific antagonist of PKC), and wortmannin or LY-294002 [selective antagonists of phosphatidylinositol-3 kinases (PI3Ks)]. These antagonists were also found to relax arterial contractions induced by low [Mg2+]o in a concentration-dependent manner. The absence of [Ca2+]o and preincubation of the cells with verapamil, TSG, heparin, or caffeine plus ryanodine markedly attenuates the transient and sustained elevations in the intracellular Ca2+ concentration ([Ca2+]i) induced by low-[Mg2+]o medium. Low [Mg2+]o-produced increases in [Ca2+]i are also suppressed markedly in the presence of Gö-6976, Bis, wortmannin, or LY-294002. The present study suggests that both Ca2+ influx through voltage-gated Ca2+ channels and Ca2+ release from intracellular stores [both Ins(1,4,5)P3sensitive and ryanodine sensitive] play important roles in low-[Mg2+]o medium-induced contractions of isolated canine basilar arteries. Such contractions are clearly associated with activation of PKC isoforms and PI3Ks.

scholarly journals Involvement of CED-3/ICE Proteases in the Apoptosis of B-Chronic Lymphocytic Leukemia Cells

Blood ◽  
1997 ◽  
Vol 89 (9) ◽  
pp. 3378-3384 ◽  
Author(s):  
Beatriz Bellosillo ◽  
Mireia Dalmau ◽  
Dolors Colomer ◽  
Joan Gil
Keyword(s):  
Chronic Lymphocytic Leukemia ◽  
Lymphocytic Leukemia ◽  
Interleukin 4 ◽  
Leukemia Cells ◽  
Parp Cleavage ◽  
Dependent Manner ◽  
Kinase C ◽  
Dose Dependent ◽  
Pkc Activation

Abstract B-chronic lymphocytic leukemia (B-CLL) is characterized by the accumulation of long-lived B lymphocytes that express high levels of Bcl-2. We examined the involvement of CED-3/ICE-like proteases in the apoptosis of B-CLL cells. One of the substrates of these proteases is poly(ADP [adenosine 5′-diphosphate]-ribose) polymerase (PARP). The effect of different factors that induce the apoptosis of B-CLL cells on the proteolytic cleavage of PARP has been studied. Treatment of B-CLL cells with different concentrations of dexamethasone (1 to 1,000 μmol/L) induced in a dose-dependent manner the cleavage of PARP. Dexamethasone induced PARP cleavage after 12 hours of incubation, which was almost complete at 48 hours. PARP cleavage during apoptosis of B-CLL cells was studied in cells from eight patients and a correlation was found between cell viability and the degree of PARP cleavage. Incubation in vitro of B-CLL cells with fludarabine for 48 hours induced PARP cleavage in all the cases studied. Protein kinase C (PKC) activation with 100 nmol/L TPA (12-O-tetradecanoylphorbol 13-acetate) or incubation with interleukin-4 (10 ng/mL) prevented either dexamethasone- or fludarabine-induced proteolysis of PARP. Incubation of B-CLL cells with the CED-3/ICE–like protease inhibitor Z-VAD.fmk inhibited spontaneous and dexamethasone-induced PARP cleavage and DNA fragmentation in a dose-dependent manner. Furthermore, Z-VAD.fmk prevented the cytotoxic effect of dexamethasone. These results indicate that CED-3/ICE–like proteases play an important role in the apoptosis of B-CLL cells.

scholarly journals Ganglioside GQ1b-induced terminal differentiation in cultured mouse keratinocytes. Phosphoinositide turnover forms the onset signal

1991 ◽  
Vol 279 (3) ◽  
pp. 665-670 ◽  
Author(s):  
Y Yada ◽  
Y Okano ◽  
Y Nozawa
Keyword(s):  
Terminal Differentiation ◽  
Keratinocyte Differentiation ◽  
Dependent Manner ◽  
Transglutaminase Activity ◽  
Phosphoinositide Turnover ◽  
Kinase C ◽  
Pre Treatment ◽  
Mouse Keratinocytes ◽  
Dose Dependent ◽  
Pkc Activation

Investigations were undertaken to see whether mouse keratinocyte differentiation was elicited by gangliosides. Among the gangliosides tested only GQ1b, a tetrasialoganglioside containing two disialosyl residues, induced keratinocyte differentiation, as indicated by the formation of cornified envelopes, enhancement of transglutaminase activity and suppression of DNA synthesis. Upon stimulation with GQ1b the mass content of Ins(1,4,5)P3 and the intracellular Ca2+ levels were markedly enhanced in a time- and dose-dependent manner, whereas no significant changes were observed with other gangliosides, thereby indicating activation of phospholipase C for the onset of keratinocyte differentiation. Furthermore, only GQ1b promoted the translocation of protein kinase C (PKC) from cytosol to membrane. Inhibition of PKC with H-7 or down-regulation of the enzyme by prolonged pre-treatment with phorbol 12,13-dibutyrate greatly suppressed transglutaminase activity and formation of cornified envelopes induced by GQ1b. These results demonstrate that the tetrasialoganglioside GQ1b generates the initial differentiation signal in mouse keratinocytes through phosphoinositide turnover, and also suggest that PKC activation may act at certain, as yet unidentified, stages of differentiation processes.

scholarly journals Bradykinin Lowers the Threshold Temperature for Heat Activation of Vanilloid Receptor 1

2002 ◽  
Vol 88 (1) ◽  
pp. 544-548 ◽  
Author(s):  
Takeshi Sugiura ◽  
Makoto Tominaga ◽  
Hirotada Katsuya ◽  
Kazue Mizumura
Keyword(s):  
Hek293 Cells ◽  
Threshold Temperature ◽  
Dependent Manner ◽  
Patch Clamp Technique ◽  
Noxious Heat ◽  
Concentration Dependent Manner ◽  
Kinase C ◽  
Vanilloid Receptor 1 ◽  
Heat Activation ◽  
Pkc Activation

Bradykinin (BK) is an inflammatory mediator that plays a pivotal role in pain and hyperalgesia to heat in inflamed tissues by exciting nociceptors and sensitizing them to heat through activation of protein kinase C (PKC). It has been suggested that the capsaicin receptor (VR1), a nociceptor-specific cation channel sensitive to noxious heat, protons, and capsaicin, is a channel that is modified by BK in these effects. In this study, we examined how BK modulates the activity of VR1. We measured VR1 currents using the patch-clamp technique in human embryonic kidney-derived (HEK293) cells expressing VR1 and B2 BK receptor. We found that BK lowered the threshold temperature for activation of VR1 currents in HEK cells down to well below the physiological body temperature in a concentration-dependent manner through PKC activation. We also demonstrated that in capsaicin-sensitive dorsal root ganglion (DRG) neurons the activation threshold of heat-induced current, which is considered to be VR-1 mediated, was lowered by BK and that this effect was also mediated by PKC. These data further support the supposition that modulation of VR1 is a mechanism for the BK-induced excitation of nociceptors and their sensitization to heat.

scholarly journals Possible involvement of Rho kinase in Ca2+sensitization and mobilization by MCh in tracheal smooth muscle

2001 ◽  
Vol 280 (6) ◽  
pp. L1218-L1224 ◽  
Author(s):  
Satoru Ito ◽  
Hiroaki Kume ◽  
Haruo Honjo ◽  
Hideki Katoh ◽  
Itsuo Kodama ◽  
...  
Keyword(s):  
Kinase Inhibitor ◽  
Isometric Force ◽  
Rho Kinase ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Kinase C ◽  
Rho Kinase Inhibitor ◽  
Intracellular Ca ◽  
Gf 109203X ◽  
Protein Kinase C Inhibitor

We examined the effects of Rho kinase on contraction and intracellular Ca2+ concentration ([Ca2+]i) in guinea pig trachealis by measuring isometric force and the fura 2 signal [340- to 380-nm fluorescence ratio (F340/F380)]. A Rho kinase inhibitor, Y-27632 (1–1,000 μM), inhibited methacholine (MCh)-induced contraction, with a reduction in F340/F380 in a concentration-dependent manner. The values of EC50 for contraction and F340/F380 induced by 1 μM MCh with Y-27632 were 27.3 ± 5.1 and 524.1 ± 31.0 μM, respectively. With 0.1 μM MCh, the values for these parameters were decreased to 1.0 ± 0.1 and 98.2 ± 6.2 μM, respectively. Tension-F340/F380 curves for MCh indicated that Y-27632 caused an ∼50% inhibition of MCh-induced contraction, without a reduction in F340/F380. These effects of Y-27632 were not inhibited by a protein kinase C inhibitor, GF-109203X. Our results indicate that inhibition of Rho kinase attenuates both Ca2+ sensitization and [Ca2+]i.

scholarly journals Inhibitory action of polyamines on protein kinase C association to membranes

1987 ◽  
Vol 247 (1) ◽  
pp. 175-180 ◽  
Author(s):  
M Moruzzi ◽  
B Barbiroli ◽  
M G Monti ◽  
B Tadolini ◽  
G Hakim ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Activation Process ◽  
Dependent Manner ◽  
Kinase C ◽  
Association Reaction ◽  
Dose Dependent ◽  
Inside Out

Physiological activation of protein kinase C requires the interaction of this enzyme with cellular membranes [Nishizuka (1986) Science 233, 305-312]. In the present work a reconstituted system of protein kinase C and human inside-out erythrocyte vesicles was utilized to study the effect in vitro of naturally occurring polyamines on the activation process of protein kinase C. The active membrane-associated complex was conveniently determined by its ability to bind radioactive phorbol ester with an exact 1:1 stoichiometry. The association reaction of the enzyme to membrane was rapid, being complete within 1 min at 25 degrees C. The addition of polyamines, particularly spermine, greatly decreased in a dose-dependent manner the amount of protein kinase C bound to membranes (i.e. in the activated form). The effect observed was quite specific, since it was dependent on the chemical structure of the polyamine and it was manifest at micromolar concentrations of the polycation; the order of potency was spermine greater than spermidine greater than putrescine. A characterization of this effect is presented and possible physiological implications are discussed.

Prostaglandin F2alpha stimulates interleukin-6 synthesis via activation of PKC in osteoblast-like cells

1997 ◽  
Vol 272 (2) ◽  
pp. E208-E211 ◽  
Author(s):  
O. Kozawa ◽  
A. Suzuki ◽  
H. Tokuda ◽  
T. Uematsu
Keyword(s):  
Phospholipase D ◽  
Phorbol Ester ◽  
Interleukin 6 ◽  
Dependent Manner ◽  
Prostaglandin F2alpha ◽  
Intact Cells ◽  
Calphostin C ◽  
Kinase C ◽  
Dose Dependent ◽  
Pkc Activation

In previous studies, we reported that prostaglandin F2alpha (PGF2alpha) stimulates phosphoinositide hydrolysis by phospholipase C and phosphatidylcholine hydrolysis by phospholipase D in osteoblast-like MC3T3-E1 cells. In the present study, we examined the effect of PGF2alpha on synthesis of interleukin-6 (IL-6) and the involvement of protein kinase C (PKC) activation in the IL-6 synthesis in these cells. PGF2alpha significantly stimulated IL-6 synthesis in a dose-dependent manner in the range between 10 nM and 10 microM. A PKC-activating phorbol ester, 12-O-tetradecanoylphorbol-13-acetate (TPA), induced IL-6 synthesis. On the contrary, 4alpha-phorbol 12,13-didecanoate, a PKC-nonactivating phorbol ester, had no effect. The synthesis of IL-6 stimulated by a combination of PGF2alpha and TPA was not additive. Staurosporine, an inhibitor for protein kinases that suppressed the TPA-induced IL-6 synthesis, significantly inhibited the PGF2alpha-induced IL-6 synthesis. Calphostin C, a highly specific PKC inhibitor, also suppressed the PGF2alpha-stimulated synthesis of IL-6. The effect of PGF2alpha on IL-6 synthesis in PKC-downregulated cells was much weaker than that in intact cells. These results strongly suggest that PGF2alpha induces IL-6 synthesis via PKC activation in osteoblast-like cells.

Importance of PKC and PI3Ks in ethanol-induced contraction of cerebral arterial smooth muscle

2001 ◽  
Vol 280 (5) ◽  
pp. H2144-H2152 ◽  
Author(s):  
Zhi-Wei Yang ◽  
Jun Wang ◽  
Tao Zheng ◽  
Bella T. Altura ◽  
Burton M. Altura
Keyword(s):  
Smooth Muscle ◽  
Intracellular Signaling ◽  
Cerebral Arteries ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Kinase C ◽  
Pkc Isoforms ◽  
Intracellular Ca ◽  
Basilar Arteries ◽  
Specific Antagonist

We investigated the relationships of two potential intracellular signaling pathways, protein kinase C (PKC) and phosphatidylinositol 3-kinases (PI3Ks), to ethanol-induced contractions in cerebral arteries. Ethanol (20–200 mM) induces concentration-dependent constriction in isolated canine basilar arteries that is inhibited in a concentration-dependent manner by pretreatment of these vessels with 10−9–10−3 M Gö-6976 (an antagonist selective for PKC-α and PKC-βI), 10−10–10−4 M bisindolylmaleimide I (a specific antagonist of PKC), and 10−10–10−4 M wortmannin or 10−8–10−2 M LY-294002 (selective antagonists of PI3Ks). Ethanol-induced increases in intracellular Ca2+ concentration (from ∼100 to ∼500 nM) in canine basilar smooth muscle cells are also suppressed markedly (∼20–70%) in the presence of a similar concentration range of Gö-6976, bisindolymaleimide I, wortmannin, or LY-294002. This study suggests that activation of PKC isoforms and PI3Ks appears to be an important signaling pathway in ethanol-induced vasoconstriction of cerebral blood vessels.

scholarly journals Ocimum sanctum leaf extracts stimulate insulin secretion from perfused pancreas, isolated islets and clonal pancreatic β-cells

2006 ◽  
Vol 189 (1) ◽  
pp. 127-136 ◽  
Author(s):  
J M A Hannan ◽  
L Marenah ◽  
L Ali ◽  
B Rokeya ◽  
P R Flatt ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Ethanol Extract ◽  
Ocimum Sanctum ◽  
Dependent Manner ◽  
Leaf Extracts ◽  
Concentration Dependent Manner ◽  
Perfused Rat Pancreas ◽  
Reduce Blood Glucose ◽  
Intracellular Ca ◽  
Physiological Pathways

Ocimum sanctum leaves have previously been reported to reduce blood glucose when administered to rats and humans with diabetes. In the present study, the effects of ethanol extract and five partition fractions of O. sanctum leaves were studied on insulin secretion together with an evaluation of their mechanisms of action. The ethanol extract and each of the aqueous, butanol and ethylacetate fractions stimulated insulin secretion from perfused rat pancreas, isolated rat islets and a clonal rat β-cell line in a concentration-dependent manner. The stimulatory effects of ethanol extract and each of these partition fractions were potentiated by glucose, isobutylmethylxanthine, tolbutamide and a depolarizing concentration of KCl. Inhibition of the secretory effect was observed with diazoxide, verapamil and Ca2+ removal. In contrast, the stimulatory effects of the chloroform and hexane partition fractions were associated with decreased cell viability and were unaltered by diazoxide and verapamil. The ethanol extract and the five fractions increased intracellular Ca2+ in clonal BRIN-BD11 cells, being partly attenuated by the addition of verapamil. These findings indicated that constituents of O. sanctum leaf extracts have stimulatory effects on physiological pathways of insulin secretion which may underlie its reported antidiabetic action.

scholarly journals Thrombin receptor peptide inhibits thrombin-induced increase in endothelial permeability by receptor desensitization.

1993 ◽  
Vol 120 (6) ◽  
pp. 1491-1499 ◽  
Author(s):  
H Lum ◽  
T T Andersen ◽  
A Siflinger-Birnboim ◽  
C Tiruppathi ◽  
M S Goligorsky ◽  
...  
Keyword(s):  
Endothelial Permeability ◽  
Thrombin Receptor ◽  
Dependent Manner ◽  
Vascular Endothelial ◽  
Amino Acid Peptide ◽  
Kinase C ◽  
Transendothelial Permeability ◽  
Dose Dependent ◽  
Peak Increase ◽  
Pkc Activation

Thrombin, a potent activator of cellular responses, proteolytically cleaves, and thereby activates its receptor. In the present study, we compared the effects of the thrombin receptor 14-amino acid peptide (TRP-14; SFLLRNPNDKYEPF), which comprises the NH2 terminus after cleavage of the thrombin receptor, and of the native alpha-thrombin on endothelial monolayer permeability. Addition of TRP-14 (1-200 microM) to bovine pulmonary artery endothelial cells increased [Ca2+]i in a dose-dependent manner. The peak increase in [Ca2+]i in response to 100 microM TRP-14 or 0.1 microM alpha-thrombin was similar (i.e., 931 +/- 74 nM and 1032 +/- 80 nM, respectively), which was followed by a slow decrease with t1/2 values of 0.73 and 0.61 min, respectively. Extracellular Ca2+ chelation with 5 mM EGTA abolished the sustained increases in [Ca2+]i induced by either TRP-14 or alpha-thrombin. alpha-thrombin (0.1 microM) increased transendothelial [125I]albumin permeability, whereas TRP-14 (1-100 microM) had no effect. Coincubation of 100 microM TRP-14 with 1 microM DIP-alpha-thrombin also did not increase permeability over control values. Stimulation of BPAEC with 0.1 microM alpha-thrombin induced translocation of protein kinase C (PKC) from the cytosol to the plasma membrane indicative of PKC activation, whereas TRP-14 had no effect at any concentration. TRP-14 at 100 microM desensitized BPAEC to thrombin-induced increases in [Ca2+]i and transendothelial permeability. The Ca2+ desensitization was reversed after approximately 60 min, and this recovery paralleled the recovery of the permeability response. These findings indicate that the TRP-14-induced Ca2+ mobilization in the absence of PKC activation is insufficient to increase endothelial permeability. In contrast, the increase in endothelial permeability after alpha-thrombin occurred in conjunction with Ca2+ mobilization as well as PKC activation. TRP-14 pretreatment prevented the alpha-thrombin-induced increase in endothelial permeability secondary to desensitization of the Ca2+ signal. The results suggest that combined cytosolic Ca2+ mobilization mediated by TRP-14 and PKC activation mediated by a TRP-14-independent pathway are dual signals responsible for the thrombin-induced increase in vascular endothelial permeability.

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