scholarly journals Kisspeptin inhibits a slow afterhyperpolarization current via protein kinase C and reduces spike frequency adaptation in GnRH neurons

2013 ◽  
Vol 304 (11) ◽  
pp. E1237-E1244 ◽  
Author(s):  
Chunguang Zhang ◽  
Oline K. Rønnekleiv ◽  
Martin J. Kelly
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Transient Receptor Potential ◽  
Critical Role ◽  
Transient Receptor Potential Channels ◽  
Spike Frequency ◽  
Spike Frequency Adaptation ◽  
Kinase C ◽  
Frequency Adaptation ◽  
Gnrh Neurons

Kisspeptin signaling via its cognate receptor G protein-coupled receptor 54 (GPR54) in gonadotropin-releasing hormone (GnRH) neurons plays a critical role in regulating pituitary secretion of luteinizing hormone and thus reproductive function. GPR54 is Gq-coupled to activation of phospholipase C and multiple second messenger signaling pathways. Previous studies have shown that kisspeptin potently depolarizes GnRH neurons through the activation of canonical transient receptor potential channels and inhibition of inwardly rectifying K+ channels to generate sustained firing. Since the initial studies showing that kisspeptin has prolonged effects, the question has been why is there very little spike frequency adaption during sustained firing? Presently, we have discovered that kisspeptin reduces spike frequency adaptation and prolongs firing via the inhibition of a calcium-activated slow afterhyperpolarization current ( IsAHP). GnRH neurons expressed two distinct IsAHP, a kisspeptin-sensitive and an apamin-sensitive IsAHP. Essentially, kisspeptin inhibited 50% of the IsAHP and apamin inhibited the other 50% of the current. Furthermore, the kisspeptin-mediated inhibition of IsAHP was abrogated by the protein kinase C (PKC) inhibitor calphostin C, and the PKC activator phorbol 12,13-dibutyrate mimicked and occluded any further effects of kisspeptin on IsAHP. The protein kinase A (PKA) inhibitors H-89 and the Rp diastereomer of adenosine 3′,5′-cyclic monophosphorothioate had no effect on the kisspeptin-mediated inhibition but were able to abrogate the inhibitory effects of forskolin on the IsAHP, suggesting that PKA is not involved. Therefore, in addition to increasing the firing rate through an overt depolarization, kisspeptin can also facilitate sustained firing through inhibiting an apamin-insensitive IsAHP in GnRH neurons via a PKC.

scholarly journals Kisspeptin Activation of TRPC4 Channels in Female GnRH Neurons Requires PIP2 Depletion and cSrc Kinase Activation

Endocrinology ◽  
2013 ◽  
Vol 154 (8) ◽  
pp. 2772-2783 ◽  
Author(s):  
Chunguang Zhang ◽  
Martha A. Bosch ◽  
Oline K. Rønnekleiv ◽  
Martin J. Kelly
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Tyrosine Kinase ◽  
Intracellular Signaling ◽  
Transient Receptor Potential ◽  
Trpc Channels ◽  
Kinase Activation ◽  
Trpc Channel ◽  
Kinase C ◽  
Gnrh Neurons

Abstract Kisspeptin signaling via its Gαq-coupled receptor GPR54 plays a crucial role in modulating GnRH neuronal excitability, which controls pituitary gonadotropins secretion and ultimately reproduction. Kisspeptin potently depolarizes GnRH neurons primarily through the activation of canonical transient receptor potential (TRPC) channels, but the intracellular signaling cascade has not been elucidated. Presently, we have established that kisspeptin activation of TRPC channels requires multiple membrane and intracellular signaling molecules. First, phosphatidylinositol-4,5-bisphosphate (PIP2) hydrolysis by phospholipase Cβ is required because whole-cell dialysis of Dioctanoylglycerol-PIP2 (DiC8-PIP2) inhibited the kisspeptin activation of TRPC channels, and the phosphatidylinositol 4-kinase inhibitor wortmannin, which attenuates PIP2 synthesis, prolonged TRPC channel activation. Using single cell RT-PCR, we identified that the mRNA for the PIP2-interacting TRPC channel subunit, TRPC4α, is expressed in GnRH neurons. Depletion of intracellular Ca2+ stores by thapsigargin and inositol 1,4,5-trisphosphate had no effect, indicating that the TRPC channels are not store-operated. Neither removing extracellular Ca2+ nor buffering intracellular Ca2+ with EGTA or BAPTA had any effect on the kisspeptin activation of the TRPC channels. However, the Ca2+ channel blocker Ni2+ inhibited the kisspeptin-induced inward current. Moreover, inhibition of protein kinase C by bisindolylmaleimide-I or calphostin C had no effect, but activation of protein kinase C by phorbol 12,13-dibutyrate occluded the kisspeptin-activated current. Finally, inhibition of the cytoplasmic tyrosine kinase cSrc by genistein or the pyrazolo-pyrimidine PP2 blocked the activation of TRPC channels by kisspeptin. Therefore, TRPC channels in GnRH neurons are receptor-operated, and kisspeptin activates TRPC channels through PIP2 depletion and cSrc tyrosine kinase activation, which is a novel signaling pathway for peptidergic excitation of GnRH neurons.

Evidence of a role for TRPC channels in VEGF-mediated increased vascular permeability in vivo

2004 ◽  
Vol 286 (3) ◽  
pp. H1015-H1026 ◽  
Author(s):  
T. M. Pocock ◽  
R. R. Foster ◽  
D. O. Bates
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Vascular Permeability ◽  
Transient Receptor Potential ◽  
Transient Receptor Potential Channels ◽  
Flufenamic Acid ◽  
Vegf Receptor ◽  
Trpc Channels ◽  
Kinase C

Vascular endothelial growth factor (VEGF) increases vascular permeability by stimulating endothelial Ca2+ influx. Here we provide evidence that links VEGF-mediated increased permeability and endothelial intracellular Ca2+ concentration ([Ca2+]i) with diacylglycerol (DAG)-mediated activation of the transient receptor potential channels (TRPCs). We used the Landis-Michel technique to measure changes in hydraulic conductivity ( Lp) and fluorescence photometry to quantify changes in endothelial [Ca2+]i in individually perfused Rana mesenteric microvessels in vivo and transfected nonendothelial cells in vitro. The membrane-permeant DAG analog 1-oleoyl-2-acetyl- sn-glycerol (OAG, 100 μM), which is known to increase Ca2+ influx through TRPCs, transiently increased Lp 3.8 ± 1.2-fold (from 1.6 ± 0.8 to 9.8 ± 2.7 × 10–7 cm·s–1·cmH2O–1; P < 0.0001; n = 18). Protein kinase C inhibition by bisindolylmaleimide (1 μM) did not affect the OAG-induced increases in Lp. OAG also significantly increased microvascular endothelial [Ca2+]i in vivo ( n = 13; P < 0.0001), which again was not sensitive to protein kinase C inhibition. VEGF induced a transient increase in endothelial [Ca2+]i in human embryonic kidney cells (HEK-293) that were cotransfected with VEGF receptor 2 and TRPC-6 but not with control, VEGF receptor 2, or TRPC-6 expression vector alone ( P < 0.01; n = 9). Flufenamic acid, which has been shown to enhance activity of TRPC-6 but inhibit TRPC-3 and -7, enhanced the VEGF-mediated increase in Lp in approximately half of the vessels tested but inhibited the response in the other half of the vessels. These data provide evidence consistent with the hypothesis that VEGF increases vascular permeability via DAG-mediated Ca2+ entry through TRPCs. Although the exact identities of the TRPCs remain to be confirmed, TRPC-6 appears to be a likely candidate in approximately half of the vessels.

Protein kinase C and chemical-induced abnormal palate development

2005 ◽  
Vol 24 (4) ◽  
pp. 203-214 ◽  
Author(s):  
Chada S Reddy
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Single Gene ◽  
Critical Role ◽  
Early Death ◽  
Palate Development ◽  
Kinase C ◽  
A Cell ◽  
Context Specific

The protein kinase C (PKC) family of proteins mediates the action of growth factors and other ligands by activating a network of transcription factors that bind to TRE sequences in the promoters of many genes that regulate cell proliferation, differentiation, extracellular matrix synthesis, apoptosis and others in a cell type-, isozymeand context-specific manner. The critical role of PKC in embryonic development is indicated by early death of embryos in which one or more of these isozymes are inactivated. Our studies together with others show that palatal PKC signalling is functional and may be essential for normal palate development. Although single gene knockouts have failed to exhibit the cleft palate (CP) phenotype, owing to compensation by other kinases, many chemicals including the mycotoxin, secalonic acid D, disrupt palatal PKC signalling leading to altered palatal mesenchymal gene expression. The potential relevance of such effects to chemical-induced CP is discussed.

scholarly journals Activation of IκB Kinase β by Protein Kinase C Isoforms

1999 ◽  
Vol 19 (3) ◽  
pp. 2180-2188 ◽  
Author(s):  
Maria-José Lallena ◽  
María T. Diaz-Meco ◽  
Gary Bren ◽  
Carlos V. Payá ◽  
Jorge Moscat
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Critical Role ◽  
Dominant Negative ◽  
Dominant Negative Mutant ◽  
Cell Functions ◽  
Kinase C ◽  
Iκb Kinase ◽  
Tnf Α

ABSTRACT The atypical protein kinase C (PKC) isotypes (λ/ιPKC and ζPKC) have been shown to be critically involved in important cell functions such as proliferation and survival. Previous studies have demonstrated that the atypical PKCs are stimulated by tumor necrosis factor alpha (TNF-α) and are required for the activation of NF-κB by this cytokine through a mechanism that most probably involves the phosphorylation of IκB. The inability of these PKC isotypes to directly phosphorylate IκB led to the hypothesis that ζPKC may use a putative IκB kinase to functionally inactivate IκB. Recently several groups have molecularly characterized and cloned two IκB kinases (IKKα and IKKβ) which phosphorylate the residues in the IκB molecule that serve to target it for ubiquitination and degradation. In this study we have addressed the possibility that different PKCs may control NF-κB through the activation of the IKKs. We report here that αPKC as well as the atypical PKCs bind to the IKKs in vitro and in vivo. In addition, overexpression of ζPKC positively modulates IKKβ activity but not that of IKKα, whereas the transfection of a ζPKC dominant negative mutant severely impairs the activation of IKKβ but not IKKα in TNF-α-stimulated cells. We also show that cell stimulation with phorbol 12-myristate 13-acetate activates IKKβ, which is entirely dependent on the activity of αPKC but not that of the atypical isoforms. In contrast, the inhibition of αPKC does not affect the activation of IKKβ by TNF-α. Interestingly, recombinant active ζPKC and αPKC are able to stimulate in vitro the activity of IKKβ but not that of IKKα. In addition, evidence is presented here that recombinant ζPKC directly phosphorylates IKKβ in vitro, involving Ser177 and Ser181. Collectively, these results demonstrate a critical role for the PKC isoforms in the NF-κB pathway at the level of IKKβ activation and IκB degradation.

Influence of Protein Kinase C and Calcium in the Course of Thrombin Receptors Activation.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 3194-3194
Author(s):  
Ying Xie ◽  
Yue Han ◽  
De Pei Wu ◽  
Aining Sun ◽  
Wei Zhang
Keyword(s):  
Protein Kinase C ◽  
Platelet Aggregation ◽  
Protein Kinase ◽  
Membrane Surface ◽  
Signal Transmission ◽  
Critical Role ◽  
Signal Pathways ◽  
Kinase C ◽  
Thrombin Receptors

Abstract Object In order to compare the functions of protein kinase C (PKC) and calcium (Ca2+) in platelet aggregation and platelet membrane surface glycoproteins GPIb expression after thrombin receptors activation, then to investigate the role of Gq signal transmission pathway in the course of thrombin receptors activation. Methods Peptide SFLLRN (PAR1-AP) and AYPGKF (PAR4-AP) were used for stimulating platelet at different time point (0, 1, 2, 5, 10, 30min), then the alterations of platelet aggregation and GPIb were analyzed in the involvement of Ro-31-2220 (inhibitor of PKC) and BAPTA/AM (calcium chelator). Results Either PAR1 or PAR4 peptide can induce absolute platelet aggregation, together with a reversible internalization of GPIb. Platelet aggregation was inhibited by Ro-31-2220 or BAPTA/AM while the shape change curve still occurred upon PARs activation. In addition, Ro-31-2220 decreases GPIb centralisation upon PAR1 stimulation (P <0.05 at 1, 2 min), though it blocks the pool of GPIb inside platelet in PAR4 activation (P <0.05 at 10, 30 min). Meanwhile, GPIb internalization was blocked by BAPTA for both peptides (P <0.05 at 1∼10 min). Conclusion All the results confirm a critical role of Gq pathway in thrombin signal transmission through the involvement of protein kinase C and calcium. Calcium is closely correlated with the thrombin receptors activation, seemed to be similar for two PARs signal pathways. Protein kinase C urges GPIb centralisation in PAR1 pathway and accelerates GPIbα return in PAR4 pathway.

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