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.

scholarly journals Mitogenic Response of Murine B Lymphocytes to Salmonella typhimurium Lipopolysaccharide Requires Protein Kinase C-Dependent Late Tyrosine Phosphorylations

1998 ◽  
Vol 66 (6) ◽  
pp. 2547-2552 ◽  
Author(s):  
Anne Mey ◽  
Jean-Pierre Revillard
Keyword(s):  
Protein Synthesis ◽  
Protein Kinase C ◽  
B Cells ◽  
Protein Kinase ◽  
Tyrosine Kinase ◽  
Kinase Inhibitors ◽  
Cross Linking ◽  
Kinase Activation ◽  
Herbimycin A ◽  
Kinase C

ABSTRACT Unlike the cross-linking of membrane immunoglobulins, the activation of B cells by lipopolysaccharide (LPS) does not involve the phosphoinositol turnover and the initial activation of tyrosine kinases. However, LPS-induced B-cell proliferation was inhibited by the tyrosine kinase inhibitors genistein and herbimycin A even when added 48 h after the beginning of the culture. Tyrosyl-phosphorylated proteins were detected by Western blotting after 24 h of culture with LPS, reaching a maximum concentration after 72 h. Late tyrosine phosphorylations were also detected in B cells activated for 72 h with anti-immunoglobulin M antibody and were abrogated by the protein synthesis inhibitor cycloheximide, the tyrosine kinase inhibitors genistein and herbimycin A, and the protein kinase C inhibitor chelerythrine. The role of protein kinase C in late tyrosine kinase activation is independent of Ca2+mobilization and was confirmed by detection of a comparable but restricted pattern of tyrosine-phosphorylated substrates in B cells treated with phorbol myristate acetate alone or in association with ionomycin. Tyrosine kinase activation was dependent on de novo protein synthesis. However, culture supernatants of LPS-activated B cells were devoid of mitogenic activity and induced a phosphorylation pattern more restricted than that achieved by LPS. Altogether these data indicate that proliferation signals induced by LPS or by the cross-linking of membrane immunoglobulins are controlled by late tyrosine phosphorylations occurring throughout the first 3 days of culture, controlled in part by protein kinase C activation, and dependent on the synthesis of an intermediate protein(s) either not secreted in the culture supernatant or present but biologically inactive in naive B cells.

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.

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.

scholarly journals Role of the kinase activation loop on protein kinase C θ activity and intracellular localisation

FEBS Letters ◽  
2003 ◽  
Vol 554 (1-2) ◽  
pp. 35-40 ◽  
Author(s):  
Bianca Sparatore ◽  
Mario Passalacqua ◽  
Marco Pedrazzi ◽  
Sabina Ledda ◽  
Mauro Patrone ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Activation Loop ◽  
Kinase Activation ◽  
Kinase C ◽  
Intracellular Localisation

scholarly journals Role of tyrosine kinase and protein kinase C in the steroidogenic actions of angiotensin II, α-melanocyte-stimulating hormone and corticotropin in the rat adrenal cortex

1995 ◽  
Vol 305 (2) ◽  
pp. 433-438 ◽  
Author(s):  
S Kapas ◽  
A Purbrick ◽  
J P Hinson
Keyword(s):  
Protein Kinase C ◽  
Angiotensin Ii ◽  
Protein Kinase ◽  
Tyrosine Kinase ◽  
Zona Glomerulosa ◽  
Aldosterone Secretion ◽  
Melanocyte Stimulating Hormone ◽  
Kinase C ◽  
Stimulating Hormone

The role of protein kinases in the steroidogenic actions of alpha-melanocyte-stimulating hormone (alpha-MSH), angiotensin II (AngII) and corticotropin (ACTH) in the rat adrenal zona glomerulosa was examined. Ro31-8220, a potent selective inhibitor of protein kinase C (PKC), inhibited both AngII- and alpha-MSH-stimulated aldosterone secretion but had no effect on aldosterone secretion in response to ACTH. The effect of Ro31-8220 on PKC activity was measured in subcellular fractions. Basal PKC activity was higher in cytosol than in membrane or nuclear fractions. Incubation of the zona glomerulosa with either alpha-MSH or AngII resulted in significant increases in PKC activity in the nuclear and cytosolic fractions and decreases in the membrane fraction. These effects were all inhibited by Ro31-8220. ACTH caused a significant increase in nuclear PKC activity only, and this was inhibited by Ro31-8220 without any significant effect on the steroidogenic response to ACTH, suggesting that PKC translocation in response to ACTH may be involved in another aspect of adrenal cellular function. Tyrosine phosphorylation has not previously been considered to be an important component of the response of adrenocortical cells to peptide hormones. Both AngII and alpha-MSH were found to activate tyrosine kinase, but ACTH had no effect, observations that have not been previously reported. Tyrphostin 23, a specific antagonist of tyrosine kinases, inhibited aldosterone secretion in response to AngII and alpha-MSH, but not ACTH. These data confirm the importance of PKC in the adrenocortical response to AngII and alpha-MSH, and, furthermore, indicate that tyrosine kinase may play a critical role in the steroidogenic actions of AngII and alpha-MSH in the rat adrenal zona glomerulosa.

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