scholarly journals Effects of insulin on the translocation of protein kinase C-θ and other protein kinase C isoforms in rat skeletal muscles

1995 ◽  
Vol 308 (1) ◽  
pp. 177-180 ◽  
Author(s):  
K Yamada ◽  
A Avignon ◽  
M L Standaert ◽  
D R Cooper ◽  
B Spencer ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Skeletal Muscles ◽  
Phorbol Esters ◽  
Kinase C ◽  
Pkc Epsilon ◽  
Pkc Isoforms ◽  
Pkc Alpha

Protein kinase C (PKC)-theta is a newly recognized major PKC isoform in skeletal muscle. In this study we found that insulin provoked rapid biphasic increases in membrane-associated immunoreactive PKC-theta, as well as PKC-alpha, PKC-beta and PKC-epsilon, in rat soleus muscles incubated in vitro. Effects of insulin on PKC isoforms in the soleus were comparable in magnitude with those of phorbol esters. Increases in membrane-associated PKC-theta, PKC-alpha, PKC-beta and PKC-epsilon were also observed in rat gastrocnemius muscles after insulin treatment in vivo. Our findings suggest that PKC-theta, like other diacylglycerol-sensitive PKC isoforms (alpha, beta and epsilon), may play a role in insulin action in skeletal muscles.

scholarly journals Insulin increases mRNA levels of protein kinase C-α and -β in rat adipocytes and protein kinase C-α, -β and -θ in rat skeletal muscle

1995 ◽  
Vol 308 (1) ◽  
pp. 181-187 ◽  
Author(s):  
A Avignon ◽  
M L Standaert ◽  
K Yamada ◽  
H Mischak ◽  
B Spencer ◽  
...  
Keyword(s):  
Adipose Tissue ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Mrna Levels ◽  
Rat Adipocytes ◽  
Kinase C ◽  
Pkc Epsilon ◽  
Pkc Alpha

Effects of insulin of levels of mRNA encoding protein kinase C (PKC)-alpha, PKC-beta, PKC-epsilon and PKC-theta were examined by ribonuclease protection assay in primary cultures of rat adipocytes in vitro, and in rat adipose tissue and gastrocnemius muscle in vivo. In all cases, insulin increased the levels of PKC-alpha mRNA and PKC-beta mRNA, and, in muscle, insulin also increased the level of PKC-theta mRNA. PKC-epsilon mRNA levels, on the other hand, were not altered significantly. Insulin also stimulated the apparent translocation of PKC-alpha, -beta, -epsilon and -theta, to the membrane fractions of adipocytes, adipose tissue and gastrocnemius muscles, and, in some instances, total PKC levels were diminished, e.g. PKC-alpha and PKC-beta in cultured adipocytes in vitro and/or whole adipose tissue in vivo, and PKC-alpha and PKC-theta in the gastrocnemius muscle. Thus, insulin-induced increases in PKC mRNA may have been partly compensatory in nature to restore PKC levels following translocation and proteolytic losses. However, much more severe depletion of PKC-alpha and PKC-beta by phorbol ester treatment in cultured rat adipocytes in vitro resulted in, if anything, smaller increases in PKC-alpha mRNA and PKC-beta mRNA, and it therefore appears that insulin effects on PKC mRNA levels were not simply due to decreases in respective PKC levels. In addition, effects of insulin, particularly on PKC-beta mRNA, could not be attributed to increased glucose metabolism, which alone decreased PKC-beta mRNA in cultured adipocytes in vitro. We conclude that insulin-induced translocation and degradation of PKC-alpha, PKC-beta and PKC-theta are attended by selective increases in their mRNAs. This mechanism of increasing mRNA may be important in maintaining PKC levels during the continued action of insulin.

PDGF and IL-1 induce and activate specific protein kinase C isoforms in mesangial cells

1996 ◽  
Vol 271 (1) ◽  
pp. F108-F113 ◽  
Author(s):  
M. B. Ganz ◽  
B. Saksa ◽  
R. Saxena ◽  
K. Hawkins ◽  
J. R. Sedor
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
De Novo ◽  
Mesangial Cells ◽  
De Novo Synthesis ◽  
Kinase C ◽  
Pkc Isoforms ◽  
Alpha Beta ◽  
Pkc Alpha

In vitro and in vivo data suggest a remarkable plasticity in the differentiated phenotype of intrinsic glomerular cells, which after injury express new structures and functions. We have shown that a protein kinase C (PKC) isoform, beta II, is expressed in diseased but not normal glomeruli. Since intrarenal cytokine synthesis has been implicated in the pathogenesis of progressive glomerular injury, we have hypothesized that these mediators induce a change in isoform profile. To test this hypothesis in vitro, we have determined whether platelet-derived growth factor (PDGF) and interleukin-1 (IL-1) alter the expression or activation of PKC isoforms in cultured mesangial cells (MCs). By immunoblot and ribonuclease (RNase) protection assays, both PDGF and IL-1 induce as early as 2 h de novo synthesis of PKC-beta II. Since MCs constitutively express PKC-alpha, -beta I, and -zeta, we also determined whether IL-1 or PDGF alter the activity of these isoforms. PDGF maximally induced translocation of PKC-alpha (10 min), -beta I (90 min), -epsilon (120 min), and -zeta (120 min) from the cytosolic to the membrane fraction. IL-1, in contrast, did not alter the distribution of alpha, beta I, or epsilon at any time measured but did induce PKC-zeta translocation. These data suggest inflammatory mediators regulate PKC isoform activity in diseased glomeruli both by de novo synthesis of unexpressed isoforms and by activation of constitutively expressed PKC isoforms.

Effects of insulin on diacylglycerol/protein kinase-C signalling and glucose transport in rat skeletal muscles in vivo and in vitro.

Endocrinology ◽  
1992 ◽  
Vol 130 (6) ◽  
pp. 3345-3355 ◽  
Author(s):  
B Yu ◽  
M Standaert ◽  
T Arnold ◽  
H Hernandez ◽  
J Watson ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Glucose Transport ◽  
Skeletal Muscles ◽  
Kinase C

Do adult rat ventricular myocytes express protein kinase C-alpha?

1997 ◽  
Vol 272 (5) ◽  
pp. H2485-H2491 ◽  
Author(s):  
V. Rybin ◽  
S. F. Steinberg
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Ventricular Myocytes ◽  
Chromatographic Purification ◽  
Adult Rat ◽  
Pkc Delta ◽  
Kinase C ◽  
Pkc Epsilon ◽  
Pkc Isoforms ◽  
Pkc Alpha

Although calcium-insensitive protein kinase C (PKC) isoforms (PKC-epsilon and PKC-delta) are consistently detected in adult ventricular myocytes, the evidence that adult ventricular myocytes also express calcium-sensitive PKC-alpha is inconsistent. The current study used four different anti-PKC-alpha-antibodies to resolve some of the uncertainties regarding the immunodetection of PKC-alpha in adult ventricular myocytes. Three of the antibodies used in this study barely (GIBCO-BRL) or rather faintly (Transduction Laboratories and Seikagaku America) recognize PKC-alpha in crude preparations from adult ventricular myocytes. Although each of these antibodies recognizes a prominent 80-kDa band, which is similar in size to PKC-alpha, this represents nonspecific immunoreactivity and should not be confused with PKC-alpha. This conclusion is based on peptide-blocking experiments (GIBCO-BRL), the absence of the requisite sensitivity to calcium- and phorbol 12-myristate 13-acetate-induced translocation (Seikagaku America and Transduction Laboratories), and/or the failure to copurify with PKC-alpha on DEAE-Sephacel chromatography. Nevertheless, an antibody from Upstate Biotechnology clearly recognizes PKC-alpha and not other unrelated nonspecific immunoreactive species in crude preparations from adult ventricular myocytes. Each of the antisera used in this study could detect PKC-alpha immunoreactivity following chromatographic purification of the samples to enrich for PKC-alpha and remove nonspecific immunoreactive proteins. These results suggest that PKC-alpha is expressed by adult ventricular myocytes and argue that differences in the sensitivity and/or specificity of available antisera contribute to at least some of the confusion regarding PKC-alpha expression in adult ventricular myocytes.

scholarly journals The regulatory domain of protein kinase C-ε restricts the catalytic-domain-specificity

1991 ◽  
Vol 276 (1) ◽  
pp. 257-260 ◽  
Author(s):  
C Pears ◽  
D Schaap ◽  
P J Parker
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Catalytic Domain ◽  
Structural Basis ◽  
Regulatory Domain ◽  
Substrate Selection ◽  
Kinase C ◽  
Pkc Epsilon ◽  
Pkc Alpha

Protein kinase C (PKC) consists of a family of closely related enzymes that can be divided into two subfamilies (alpha, beta and gamma and delta, epsilon and zeta) on the basis of primary sequence. Functional differences have also been described; thus PKC-alpha, PKC-beta and PKC-gamma readily phosphorylate histone IIIS in vitro, whereas PKC-epsilon will not employ this substrate efficiently. We have previously demonstrated, however, that proteolytic cleavage of PKC-epsilon generates a constitutive kinase activity that is an efficient histone IIIS kinase [Schaap, Hsuan, Totty & Parker (1990) Eur. J. Biochem. 191, 431-435]. In order to investigate the structural basis for this switch in specificity, we have constructed a chimaeric protein containing the regulatory domain of PKC-epsilon fused to the catalytic domain of PKC-gamma. When this is expressed in COS1 cells the chimaeric kinase shows a substrate-specificity similar to that of PKC-epsilon rather than to that of PKC-gamma. This demonstrates a role for the regulatory domain in substrate selection of PKC-epsilon.

scholarly journals Differential spatial and temporal phosphorylation of the visual receptor, rhodopsin, at two primary phosphorylation sites in mice exposed to light

2003 ◽  
Vol 374 (2) ◽  
pp. 537-543 ◽  
Author(s):  
Ryan A. ADAMS ◽  
Xinran LIU ◽  
David S. WILLIAMS ◽  
Alexandra C. NEWTON
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Outer Segment ◽  
Phorbol Esters ◽  
Phosphorylation Sites ◽  
Rod Outer Segment ◽  
Kinase C ◽  
Rhodopsin Kinase

Phosphorylation of rhodopsin critically controls the visual transduction cascade by uncoupling it from the G-protein transducin. The kinase primarily responsible for this phosphorylation is rhodopsin kinase, a substrate-regulated kinase that phosphorylates light-activated rhodopsin. Protein kinase C has been implicated in controlling the phosphorylation of both light-activated and dark-adapted rhodopsin. Two of the major rhodopsin phosphorylation sites in vivo, Ser334 and Ser338, are effective protein kinase C phosphorylation sites in vitro, while the latter is preferentially phosphorylated by rhodopsin kinase in vitro. Using phosphospecific antibodies against each of these two sites, we show that both sites are under differential spatial and temporal regulation. Exposure of mice to light results in rapid phosphorylation of Ser338 that is evenly distributed along the rod outer segment. Phosphorylation of Ser334 is considerably slower, begins at the base of the rod outer segment, and spreads to the top of the photoreceptor over time. In addition, we show that phosphorylation of both sites is abolished in rhodopsin kinase−/− mice, revealing an absolute requirement for rhodopsin kinase to phosphorylate rhodopsin. This requirement may reflect the need for priming phosphorylations at rhodopsin kinase sites allowing for subsequent phosphorylation by protein kinase C at Ser334. In this regard, treatment of mouse retinas with phorbol esters results in a 4-fold increase in phosphorylation on Ser334, with no significant effect on the phosphorylation of Ser338. Our results are consistent with light triggering rapid priming phosphorylations of rhodopsin by rhodopsin kinase, followed by a slower phosphorylation on Ser334, which is regulated by protein kinase C.

Calcitonin causes a sustained inhibition of protein kinase C-stimulated bone resorption in contrast to the transient inhibition of parathyroid hormone-induced bone resorption

1990 ◽  
Vol 123 (3) ◽  
pp. 251-256 ◽  
Author(s):  
Maria Ransjö ◽  
Ulf H. Lerner
Keyword(s):  
Protein Kinase C ◽  
Parathyroid Hormone ◽  
Protein Kinase ◽  
Bone Resorption ◽  
Phorbol Esters ◽  
Inhibitory Effect ◽  
Prostaglandin E ◽  
Kinase C

Abstract. Calcitonin is a well known inhibitor of osteoclastic bone resorption, both in vivo and in vitro. However, it is also known that calcitonin has only a transient inhibitory effect on bone resorption. The mechanism for this so-called "escape from inhibition" phenomenon is not clear. In the present study, the inhibitory effect of calcitonin on phorbol ester-induced bone resorption was examined in cultured neonatal mouse calvaria. Bone resorption was assessed as the release of radioactivity from bones prelabelled in vivo with 45Ca. Two protein kinase C-activating phorbol esters, phorbol-12-myristate-13-acetate and phorbol-12,13-dibutyrate, both stimulated 45Ca release in 120-h cultures at a concentration of 10 nmol/l. Calcitonin (30 nmol/l) inhibited phorbol esterstimulated bone resorption without any "escape from inhibition". This was in contrast to the transient inhibitory effect of calcitonin on bone resorption stimulated by parathyroid hormone (10 nmol/l), prostaglandin E2 (2 μmol/l), and bradykinin (1 μmol/l). Our results suggest that activation of protein kinase C produces a sustained inhibitory effect of calcitonin on bone resorption.

scholarly journals Effects of insulin and phorbol esters on subcellular distribution of protein kinase C isoforms in rat adipocytes

1992 ◽  
Vol 288 (1) ◽  
pp. 319-323 ◽  
Author(s):  
R V Farese ◽  
M L Standaert ◽  
A J Francois ◽  
K Ways ◽  
T P Arnold ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Subcellular Distribution ◽  
Phorbol Esters ◽  
Rat Adipocytes ◽  
Kinase C ◽  
Pkc Zeta ◽  
Pkc Isoforms ◽  
Pkc Alpha

Effects of insulin and phorbol esters on subcellular distribution of protein kinase C (PKC) isoforms were examined in rat adipocytes. Both agonists provoked rapid decreases in cytosolic, and/or increases in membrane, immunoreactive PKC-alpha, PKC-beta, PKC-gamma, and PKC-epsilon. Effects of phorbol esters on PKC-alpha redistribution to the plasma membrane, however, were much greater than those of insulin. In contrast, insulin, but not phorbol esters, stimulated the translocation of PKC-beta to the plasma membrane, and provoked changes in PKC-zeta redistribution. Neither agonist altered subcellular distribution of PKC-delta, which was detected only in membrane fractions. Our findings indicate that insulin and phorbol esters have overlapping and distinctly different effects on the subcellular redistribution of specific PKC isoforms.

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