scholarly journals Modulatory effect of protein kinase C on thapsigargin-induced calcium entry in thyroid FRTL-5 cells

1993 ◽  
Vol 290 (2) ◽  
pp. 443-447 ◽  
Author(s):  
K Törnquist
Keyword(s):  
Plasma Membrane ◽  
Protein Kinase C ◽  
Membrane Potential ◽  
Protein Kinase ◽  
Calcium Influx ◽  
Initial Increase ◽  
Plateau Phase ◽  
Kinase C ◽  
Measure Membrane Potential ◽  
Plateau Level

The aim of the present study was to investigate the regulation of calcium influx in thyroid FRTL-5 cells. Stimulating Fura 2-loaded cells with thapsigargin rapidly increased the cytosolic Ca2+ concentration ([Ca2+]i), which then stabilized at a new elevated plateau level. The initial increase in [Ca2+]i consisted mainly of the release of sequestered Ca2+. The plateau phase was totally dependent on extracellular Ca2+. The influx of Ca2+ was blocked by Ni2+ and was decreased in depolarized cells. The importance of protein kinase C in regulating influx of Ca2+ was then evaluated. Addition of the phorbol ester 12-O-tetradecanoylphorbol 13-acetate prior to thapsigargin significantly decreased the influx of extracellular Ca2+. Studies with bisoxonol to measure membrane potential showed that TPA depolarized the plasma membrane in FRTL-5 cells. In cells where protein kinase C was downregulated or was inhibited by staurosporine, the thapsigargin-induced influx of Ca2+ was enhanced. The results indicate that emptying intracellular Ca2+ pools is sufficient to induce influx of Ca2+ in FRTL-5 cells, and that protein kinase C has a modulatory effect on this process.

scholarly journals Regulated CD44 Cleavage under the Control of Protein Kinase C, Calcium Influx, and the Rho Family of Small G Proteins

1999 ◽  
Vol 274 (36) ◽  
pp. 25525-25534 ◽  
Author(s):  
Isamu Okamoto ◽  
Yoshiaki Kawano ◽  
Mitsuhiro Matsumoto ◽  
Moritaka Suga ◽  
Kozo Kaibuchi ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
G Proteins ◽  
Calcium Influx ◽  
Kinase C ◽  
Rho Family ◽  
Small G Proteins

scholarly journals Cytoplasmic [Ca2+] and intracellular pH in lymphocytes. Role of membrane potential and volume-activated Na+/H+ exchange.

1987 ◽  
Vol 89 (2) ◽  
pp. 185-213 ◽  
Author(s):  
S Grinstein ◽  
S Cohen
Keyword(s):  
Protein Kinase C ◽  
Membrane Potential ◽  
Protein Kinase ◽  
Intracellular Ph ◽  
Enzyme Treatment ◽  
Membrane Hyperpolarization ◽  
Kinase C ◽  
Free Media ◽  
Stimulation Of

The effect of elevating cytoplasmic Ca2+ [( Ca2+]i) on the intracellular pH (pHi) of thymic lymphocytes was investigated. In Na+-containing media, treatment of the cells with ionomycin, a divalent cation ionophore, induced a moderate cytoplasmic alkalinization. In the presence of amiloride or in Na+-free media, an acidification was observed. This acidification is at least partly due to H+ (equivalent) uptake in response to membrane hyperpolarization since: it was enhanced by pretreatment with conductive protonophores, it could be mimicked by valinomycin, and it was decreased by depolarization with K+ or gramicidin. In addition, activation of metabolic H+ production also contributes to the acidification. The alkalinization is due to Na+/H+ exchange inasmuch as it is Na+ dependent, amiloride sensitive, and accompanied by H+ efflux and net Na+ gain. A shift in the pHi dependence underlies the activation of the antiport. The effect of [Ca2+]i on Na+/H+ exchange was not associated with redistribution of protein kinase C and was also observed in cells previously depleted of this enzyme. Treatment with ionomycin induced significant cell shrinking. Prevention of shrinking largely eliminated the activation of the antiport. Moreover, a comparable shrinking produced by hypertonic media also activated the antiport. It is concluded that stimulation of Na+/H+ exchange by elevation of [Ca2+]i is due, at least in part, to cell shrinking and does not require stimulation of protein kinase C.

Protein kinase C(alpha) actively downregulates through caveolae-dependent traffic to an endosomal compartment

2000 ◽  
Vol 113 (14) ◽  
pp. 2575-2584
Author(s):  
C. Prevostel ◽  
V. Alice ◽  
D. Joubert ◽  
P.J. Parker
Keyword(s):  
Plasma Membrane ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Initial Step ◽  
Receptor Internalization ◽  
Similar Process ◽  
Receptor Desensitization ◽  
Kinase C ◽  
Annexin I ◽  
Pkc Alpha

Receptor desensitization occurs through receptor internalization and targeting to endosomes, a prerequisite for sorting and degradation. Such trafficking processes may not be restricted to membrane associated receptors but may also play an important role in the downregulation of cytoplasmic transducers such as protein kinase C (PKC). It is demonstrated here that acute TPA exposure induces the transport of activated PKC(alpha) from the plasma membrane to endosomes. This process requires PKC activity and catalytically competent PKC can even promote a similar process for a truncated regulatory domain PKC(α) protein. It is established that PKC(α) is targeted to the endosome compartment as an active kinase, where it colocalizes with annexin I, a substrate of PKC. Thus, PKC(alpha) downregulation shares features with plasma membrane associated receptor sorting and degradation. However, it is shown that PKC(α) delivery to the endosome compartment is not a Rab5 mediated process in contrast to the well characterised internalisation of the transferrin receptor. An alternative route for PKC(alpha) is evidenced by the finding that the cholesterol binding drugs nystatin and filipin, known to inhibit caveolae mediated trafficking, are able to block PKC(alpha) traffic and down regulation. Consistent with this, the endosomes where PKC(alpha) is found also contain caveolin. It is concluded that the initial step in desensitisation of PKC(alpha) involves active delivery to endosomes via a caveolae mediated process.

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