PKC-independent inhibition of cardiac L-type Ca2+ channel current by phorbol esters

1996 ◽  
Vol 270 (2) ◽  
pp. H620-H627 ◽  
Author(s):  
T. Asai ◽  
L. M. Shuba ◽  
D. J. Pelzer ◽  
T. F. McDonald
Keyword(s):  
Protein Kinase C ◽  
Phorbol Esters ◽  
Ventricular Myocytes ◽  
Inhibitory Effect ◽  
Independent Action ◽  
Independent Manner ◽  
Channel Current ◽  
Kinase C ◽  
Channel Currents ◽  
Stimulation Of

Active and inactive phorbol esters were applied to guinea pig ventricular myocytes to study the responses of L-type Ca2+ (ICa,L) and L-type Na+ (INa,L) currents. Phorbol 12-myristate 13-acetate (PMA) (10-100 rM) never stimulated ICa,L or INa,L and frequently depressed them by 5-30% in a voltage-independent manner. However, the phorbol ester consistently activated delayed-rectifying K+ (IK) and Cl- currents. The inhibition of ICa,L occurred approximately 3 times faster than comonitored stimulation of IK, and ICa,L and INa,L were unaffected by two interventions that suppressed IK stimulation [pretreatment with 50 microM 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H-7) and dialysis with pCa 11 versus standard pCa 9 solution]. Inactive phorbol esters 4 alpha-phorbol 12,13-didecanoate (alpha-PDD) and 4 alpha-phorbol had little effect on IK, but alpha-PDD had a PMA-like inhibitory effect on Ca2+ channel currents. We conclude that, unlike the stimulation of IK by PMA, inhibition of Ca2+ channel current by phorbol esters is a protein kinase C-independent action.

scholarly journals Bombesin and platelet-derived growth factor stimulate formation of inositol phosphates and Ca2+ mobilization in Swiss 3T3 cells by different mechanisms

1989 ◽  
Vol 258 (1) ◽  
pp. 177-185 ◽  
Author(s):  
D M Blakeley ◽  
A N Corps ◽  
K D Brown
Keyword(s):  
Protein Kinase C ◽  
Growth Factor ◽  
Protein Kinase ◽  
Phorbol Esters ◽  
Inositol Phosphates ◽  
Platelet Derived Growth Factor ◽  
3T3 Cells ◽  
Kinase C ◽  
Swiss 3T3 ◽  
Stimulation Of

Highly purified platelet-derived growth factor (PDGF) or recombinant PDGF stimulate DNA synthesis in quiescent Swiss 3T3 cells. The dose-response curves for the natural and recombinant factors were similar, with half-maximal responses at 2-3 ng/ml and maximal responses at approx. 10 ng/ml. Over this dose range, both natural and recombinant PDGF stimulated a pronounced accumulation of [3H]inositol phosphates in cells labelled for 72 h with [3H]inositol. In addition, mitogenic concentrations of PDGF stimulated the release of 45Ca2+ from cells prelabelled with the radioisotope. However, in comparison with the response to the peptide mitogens bombesin and vasopressin, a pronounced lag was evident in both the generation of inositol phosphates and the stimulation of 45Ca2+ efflux in response to PDGF. Furthermore, although the bombesin-stimulated efflux of 45Ca2+ was independent of extracellular Ca2+, the PDGF-stimulated efflux was markedly inhibited by chelation of external Ca2+ by using EGTA. Neither the stimulation of formation of inositol phosphates nor the stimulation of 45Ca2+ efflux in response to PDGF were affected by tumour-promoting phorbol esters such as 12-O-tetradecanoylphorbol 13-acetate (TPA). In contrast, TPA inhibited phosphoinositide hydrolysis and 45Ca2+ efflux stimulated by either bombesin or vasopressin. Furthermore, whereas formation of inositol phosphates in response to both vasopressin and bombesin was increased in cells in which protein kinase C had been down-modulated by prolonged exposure to phorbol esters, the response to PDGF was decreased in these cells. These results suggest that, in Swiss 3T3 cells, PDGF receptors are coupled to phosphoinositidase activation by a mechanism that does not exhibit protein kinase C-mediated negative-feedback control and which appears to be fundamentally different from the coupling mechanism utilized by the receptors for bombesin and vasopressin.

Autoregulation of muscarinic and gastrin receptors on gastric parietal cells

1989 ◽  
Vol 256 (2) ◽  
pp. G356-G363 ◽  
Author(s):  
T. Chiba ◽  
S. K. Fisher ◽  
B. W. Agranoff ◽  
T. Yamada
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Parietal Cell ◽  
Phorbol Esters ◽  
Cell Function ◽  
Inhibitory Effect ◽  
Parietal Cells ◽  
Kinase C ◽  
Protein Kinase C Activity ◽  
Inositol Phospholipids

In previous studies we demonstrated that parietal cell stimulation with gastrin and carbamoylcholine (carbachol) is accompanied by increased turnover of membrane inositol phospholipids. We conducted the present studies to examine whether membrane-associated protein kinase C activity is enhanced as a consequence of these events and to explore the role of this enzyme in regulating parietal cell function. We observed that carbachol and gastrin dose dependently increased membrane-associated protein kinase C activity while histamine did not. Furthermore, compounds such as phorbol esters and diacylglycerol, which are known to be direct stimulants of protein kinase C activity, also stimulated parietal cell aminopyrine uptake. In contrast, the phorbol ester 12-O-tetradecanoylphorbol-13-acetate and the synthetic diacylglycerol 1-oleoyl-2-acetyl-sn-glycerol inhibited both aminopyrine uptake and membrane inositol phospholipid turnover in parietal cells induced by carbachol and gastrin. The inhibitory effect appeared to result from reduction in the quantity of muscarinic and gastrin receptors without alterations in their specific affinities. These data suggest that protein kinase C mediates stimulation of parietal cells by gastrin and carbachol but also activates an autoregulatory mechanism via downregulation of muscarinic and gastrin receptors.

scholarly journals Protein kinase C-dependent and -independent mechanisms regulating the parotid substance P receptor as revealed by differential effects of protein kinase C inhibitors

1988 ◽  
Vol 256 (2) ◽  
pp. 677-680 ◽  
Author(s):  
H Sugiya ◽  
J W Putney
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Substance P ◽  
Time Course ◽  
Phorbol Esters ◽  
Inhibitory Effect ◽  
Protein Kinase C Inhibitors ◽  
Kinase C ◽  
Substance P Receptor ◽  
Rat Parotid

Substance P-induced inositol trisphosphate (InsP3) formation was inhibited by 1 microM-4 beta-phorbol 12,13-dibutyrate (PDBu) in rat parotid acinar cells. The inhibitory effect of PDBu was reversed by the protein kinase C inhibitors H-7 or K252a. Substance P also elicits a persistent desensitization of subsequent substance P-stimulated InsP3 formation. However, this desensitization was not inhibited by H-7. In addition, H-7 had no effect on the time course of substance P-induced InsP3 formation. These results suggest that, although activation of protein kinase C by phorbol esters can inhibit the substance P receptor-linked phospholipase C pathway, this mechanism apparently plays little, if any, role in regulating this system after activation by substance P.

scholarly journals Osmotic and phorbol ester-induced activation of Na+/H+ exchange: possible role of protein phosphorylation in lymphocyte volume regulation.

1985 ◽  
Vol 101 (1) ◽  
pp. 269-276 ◽  
Author(s):  
S Grinstein ◽  
S Cohen ◽  
J D Goetz ◽  
A Rothstein
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phorbol Ester ◽  
Time Course ◽  
Phorbol Esters ◽  
Underlying Mechanism ◽  
Atp Depletion ◽  
Sequence Of Events ◽  
Kinase C ◽  
Stimulation Of

The Na+/H+ antiport is stimulated by 12-O-tetradecanoylphorbol-13, acetate (TPA) and other phorbol esters in rat thymic lymphocytes. Mediation by protein kinase C is suggested by three findings: (a) 1-oleoyl-2-acetylglycerol also activated the antiport; (b) trifluoperazine, an inhibitor of protein kinase C, blocked the stimulation of Na+/H+ exchange; and (c) activation of countertransport was accompanied by increased phosphorylation of specific membrane proteins. The Na+/H+ antiport is also activated by osmotic cell shrinking. The time course, extent, and reversibility of the osmotically induced and phorbol ester-induced responses are similar. Moreover, the responses are not additive and they are equally susceptible to inhibition by trifluoperazine, N-ethylmaleimide, and ATP depletion. The extensive analogies between the TPA and osmotically induced effects suggested a common underlying mechanism, possibly activation of a protein kinase. It is conceivable that osmotic shrinkage initiates the following sequence of events: stimulation of protein kinase(s) followed by activation of the Na+/H+ antiport, resulting in cytoplasmic alkalinization. The Na+ taken up through the antiport, together with the HCO3- and Cl- accumulated in the cells as a result of the cytoplasmic alkalinization, would be followed by osmotically obliged water. This series of events could underlie the phenomenon of regulatory volume increase.

On the signal transducing mechanisms involved in the synergistic interaction between interleukin-1 and bradykinin on prostaglandin biosynthesis in human gingival fibroblasts

1992 ◽  
Vol 12 (4) ◽  
pp. 263-271 ◽  
Author(s):  
Ulf H. Lerner ◽  
Gustaf Brunius ◽  
Thomas Modeer
Keyword(s):  
Arachidonic Acid ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Cyclic Amp ◽  
Phorbol Esters ◽  
Synergistic Interaction ◽  
Human Gingival Fibroblasts ◽  
Gingival Fibroblasts ◽  
Kinase C ◽  
Stimulation Of

Recombinant human interleukin-1β (IL-1β) and bradykinin (BK) synergistically stimulate prostaglandin E2 (PGE2) formation in human gingival fibroblasts cultured for 24 h. Neither BK or IL-1β per se, nor their combinations, caused any acute stimulation of cellular cyclic AMP accumulation. BK, but not IL-1β, caused a rapid, transient rise of intracellular Ca2+ concentration ([Ca2+]i), as assessed by recordings of fura-2 fluorescence in monolayers of prelabelled gingival fibroblasts. IL-1β did not change the effect of BK on [Ca2+]i. Ionomycin and A 23187, two calcium ionophores, synergistically potentiated the stimulatory effect of IL-1β on PGE2 formation. Three different phorbol esters known to activate protein kinase C also synergistically potentiated the action of IL-1β on PGE2 formation. Exogenously added arachidonic acid significantly enhanced the basal formation of PGE2. In IL-1β treated cells, the enhancement of PGE2 formation seen after addition of arachidonic acid, was synergistically upregulated by IL-1β. These data show that i) the synergistic interaction between IL-1β and BK on PGE2 formation is not due to an effect linked to an upregulation of cyclic AMP or [Ca2+]i; ii) the signal transducing mechanism by which BK interacts with IL-1β, however, may be linked to a BK induced stimulation of [Ca2+]i and/or protein kinase C; iii) the mechanism involved in the action of IL-1β may, at least partly, be due to enhancement of the biosynthesis of prostanoids mediated by an upregulation of cyclooxygenase activity.

scholarly journals Involvement of calcium-sensitive phospholipid-dependent protein kinase in control of acid secretion by isolated rat parietal cells

1985 ◽  
Vol 232 (2) ◽  
pp. 609-611 ◽  
Author(s):  
N G Anderson ◽  
P J Hanson
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Acid Secretion ◽  
Phorbol Esters ◽  
Inhibitory Effect ◽  
Dependent Protein Kinase ◽  
Kinase C ◽  
Protein Kinase C Activity ◽  
Dependent Protein ◽  
Isolated Rat

The relative potency with which phorbol esters inhibited histamine-stimulated aminopyrine accumulation (an index of acid secretion) paralleled that which has been established for the activation of purified protein kinase C. The inhibitory effect of 1-oleoyl-2-acetylglycerol on aminopyrine accumulation stimulated by various secretagogues was similar to that of 12-O-tetradecanoylphorbol 13-acetate. Protein kinase C activity was present in a parietal-cell-enriched fraction. In conclusion, protein kinase C could be involved in mechanisms regulating gastric acid secretion.

Cellular variability in the development of tight junctions after activation of protein kinase C

1992 ◽  
Vol 263 (2) ◽  
pp. F293-F300 ◽  
Author(s):  
B. Ellis ◽  
E. E. Schneeberger ◽  
C. A. Rabito
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Tight Junction ◽  
Tight Junctions ◽  
Phorbol Esters ◽  
Prolonged Exposure ◽  
Inhibitory Effect ◽  
Initial Increase ◽  
Kinase C ◽  
Continuous Presence

Phorbol 12-myristate 13-acetate (PMA) decreases the tight junction conductance (TJC) during the reorganization of LLC-PK1A monolayers, but has the opposite effect in LLC-PK1B4, MDCK, and MDCK4 cells. Because no protein synthesis was required for the effects of PMA on the TJC of LLC-PK1A monolayers, we conclude that the regulation of the tight junction by protein kinase C (PKC) is a posttranslational event. In LLC-PK1A monolayers with existing tight junctions, PMA produced an initial increase in the TJC that reverted later to control values despite the continuous presence of PMA and cycloheximide. The inhibitory effect of PMA on the other cell lines was not revertible. A downregulation of total PKC activity and phorbol ester receptors was only observed during the reorganization of LLC-PK1A monolayers. PMA further increases this downregulation. This indicates that the peculiar response to PMA observed in LLC-PK1A monolayers is the result of two concurrent events: 1) the early activation of the enzyme just before the reorganization of the tight junctions begin, and 2) its late downregulation induced after prolonged exposure to phorbol esters. We conclude that PKC regulates the development of the occluding junctions, but through different mechanisms dependent on the characteristics of the cells.

Phorbol esters inhibit ammoniagenesis and gluconeogenesis in proximal tubular segments

1987 ◽  
Vol 252 (6) ◽  
pp. F1073-F1079
Author(s):  
M. C. Chobanian ◽  
M. R. Hammerman
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Proximal Tubule ◽  
Phorbol Ester ◽  
Phorbol Esters ◽  
Extracellular Ph ◽  
Linear Functions ◽  
Kinase C ◽  
Proximal Tubular ◽  
Stimulation Of

To characterize the regulation of ammoniagenesis and gluconeogenesis in renal proximal tubule, ammonia and glucose productions were measured in suspensions of canine proximal tubular segments incubated with 10 mM L-glutamine. Productions were linear functions of time for 120 min and were decreased as extracellular pH was increased from 7.0 to 7.5 To ascertain whether activation of protein kinase c affects either process, we incubated segments with tumor-promoting phorbol esters, 12-O-tetradecanoylphorbol-13-acetate (TPA), or phorbol 12,13-dibutyrate, or with the inactive phorbol ester 4 alpha-phorbol. Ammoniagenesis and gluconeogenesis were inhibited by incubation with 10(-6) M of the two former compounds but not the latter compound. Inhibition of ammoniagenesis and gluconeogenesis occurred after incubation with as little as 10(-9) M phorbol 12,13-dibutyrate. Phorbol ester-induced inhibition was observed under conditions such that extracellular [Na+] was greater than intracellular [Na+], but not when extracellular [Na+] equaled intracellular [Na+], and was not observed in the presence of amiloride. Our findings are consistent with a role for protein kinase c in the control of ammoniagenesis and gluconeogenesis in proximal tubule. Such control could be mediated via stimulation of Na+-H+ exchange.

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