![]()
|
|
||||||||
From the The protein kinase C family of enzymes transduces the myriad of
signals promoting lipid hydrolysis. The prevalence of this enzyme
family in signaling is exemplified by the diverse transduction
mechanisms that result in the generation of protein kinase C's
activator, diacylglycerol. Signals that stimulate members of the large
families of G protein-coupled receptors, tyrosine kinase receptors, or
non-receptor tyrosine kinases can cause diacylglycerol production,
either rapidly by activation of specific phospholipase Cs or more
slowly by activation of phospholipase D to yield phosphatidic acid and
then diacylglycerol(1, 2, 3) . In addition,
fatty acid generation by phospholipase A2 activation modulates protein
kinase C activity(3) . Thus, multiple receptor pathways feeding
into multiple lipid pathways have the common end result of activating
protein kinase C by production of its second messenger. Phorbol
esters, potent tumor promoters, can substitute for diacylglycerol in
activating protein kinase C(1, 2, 3) . Unlike
diacylglycerol, phorbol esters are not readily metabolized, and
treatment of cells with these molecules results in prolonged activation
of protein kinase C. As a result, phorbol esters have proved invaluable
in dissecting out protein kinase C-catalyzed phosphorylations in
vivo. In addition to regulation by diacylglycerol or phorbol
esters, all isozymes of protein kinase C require phosphatidylserine, an
acidic lipid located exclusively on the cytoplasmic face of membranes,
and some isozymes require Ca Members of the protein kinase C family are a single
polypeptide, comprised of an N-terminal regulatory region
(approximately 20-40 kDa) and a C-terminal catalytic region
(approximately 45 kDa) (Fig. 1). Cloning of the first isozymes
in the mid-1980s revealed four conserved domains:
C1-C4(8) . Each is a functional module, and many
unrelated proteins have one or the other(9) . The function of
each of these domains has been established by extensive biochemical and
mutational analysis; the C1 domain contains a Cys-rich motif,
duplicated in most isozymes, that forms the diacylglycerol/phorbol
ester binding site (Fig. 1, orange) (7) ; this
domain is immediately preceded by an autoinhibitory pseudosubstrate
sequence (Fig. 1, green)(10) ; the C2 domain
contains the recognition site for acidic lipids and, in some isozymes,
the Ca
Figure 1:
Schematic
representation of the primary structure of conventional, novel, and
atypical protein kinase Cs. Indicated are the pseudosubstrate domain (green), C1 domain comprising one or two Cys-rich motifs (orange), C2 domain (yellow) in the regulatory half,
and the ATP-binding lobe (C3, pink) and substrate-binding lobe
(C4, teal blue) of the catalytic region. The C2 domain of
novel protein kinase Cs lacks amino acids involved in binding calcium
but has key conserved residues involved in maintaining the C2 fold
(hence its description as ``C2-like''). Atypical protein
kinase Cs have only one Cys-rich motif, and phorbol ester binding has
not been detected.
To date, 11
protein kinase C isozymes have been identified and classified into
three groups based on their structure and cofactor
regulation(3) . The best characterized and first discovered are
the conventional protein kinase Cs: The
crystal structure of the second Cys-rich repeat from the C1 domain of
protein kinase C
Figure 2:
Structures of protein kinase C's
domains. A, C1 domain. The ribbon and surface diagram of amino
acids 231-280 in the second Cys-rich domain of protein kinase C
The crystal
structure of the C2 domain of synaptotagmin, elucidated by Sprang and
co-workers(17) , reveals how the other half of the regulatory
region of protein kinase C folds. Fig. 2B shows the
core of this domain (``C2 key''): 5 aspartate residues form
the Ca A
modeled structure of the catalytic domain of protein kinase C
Protein kinase C typically phosphorylates serine or threonine
residues in basic sequences but displays significantly less specificity
than protein kinase A(29) . First, unlike protein kinase
A(29) , no clear requirements for positive charge at specific
positions are apparent from analysis of sequences around
phosphorylation sites (30, 31, 32) or from
analysis of synthetic peptide
substrates(23, 26, 33) . Second, protein
kinase C displays lower stereospecificity than protein kinase A (25) , phosphorylating both D- and L-stereoisomers of Protein kinase
C also autophosphorylates in vitro(34, 35) by an intramolecular mechanism (36) at the N
terminus, hinge, and C terminus(37) ; the latter site is a poor in vitro site because it is almost quantitatively
phosphorylated in vivo (see below). In addition to
catalyzing phosphorylation reactions, protein kinase C has ATPase and
phosphatase activity. The enzyme catalyzes a cofactor-dependent and
substrate-stimulated hydrolysis of ATP(38) , and it can work
backwards (i.e. as a phosphatase) in the presence of excess
ADP. (
A key regulator of protein kinase C function in vivo is
likely to be subcellular distribution of both the enzyme and substrate (40) . Protein kinase C isozymes are distributed differentially
throughout the cell (and differently among many cell
types)(39) , and a number of targetting proteins have been
described(40) . Deciphering the specific functions of
isozymes likely awaits the development of isozyme-specific
inhibitors(41) . The application of combinatorial chemistry
toward this goal has provided the first isozyme-specific
inhibitor(42) ; similar specificity using antisense DNA has
been demonstrated for in situ studies(43) . The function of protein kinase C is regulated by two equally
important mechanisms. First, the enzyme is rendered catalytically
competent by phosphorylations that correctly align residues for
catalysis and localize protein kinase C to the cytosol. Second, binding
of ligands or, in some cases, substrate activates the enzyme by
removing the pseudosubstrate from the substrate-binding site. Biochemical experiments have established that, as
predicted(10) , activation of protein kinase C is accompanied
by removal of its pseudosubstrate from the kinase
core(20, 44) . Specifically, the basic pseudosubstrate
is protected from proteolysis when the enzyme is not catalytically
active but becomes highly sensitive to proteolysis by trypsin or
endoproteinase Arg-C upon activation(44) . Importantly, the
pseudosubstrate is unmasked whether protein kinase C is activated by
conventional (phosphatidylserine, diacylglycerol, and
Ca
Diacylglycerol and phorbol
esters serve as hydrophobic anchors to recruit protein kinase C to the
membrane; they cause a dramatic increase in the enzyme's membrane
affinity ( In addition to increasing
protein kinase C's membrane affinity, C1 ligands may also
stabilize the active conformation of protein kinase C. Diacylglycerol
doubles the catalytic efficiency of enzyme that is bound to
phosphatidylserine(57, 59, 62, 63) ;
it also stimulates the activation promoted by fatty acids (3) and short chained phosphatidylcholines(45) . C1
ligands markedly reduce the concentration of Ca
In the absence of C1 ligands,
protein kinase C binds acidic lipids with little selectivity for the
headgroup beyond the requirement for negative charge (59) (this
interaction is Ca
Figure 3:
Model for the regulation of protein kinase
C by 1) phosphorylation and 2) membrane binding and pseudosubstrate
release. Newly synthesized protein kinase C (PKC) associates
with the detergent-insoluble fraction of cells (72) (bottom
left). It is processed to the mature, cytosolic form by three
functionally distinct phosphorylations: transphosphorylation at the
activation loop to render the kinase catalytically competent (Thr-500
in
The presence of diacylglycerol causes a
striking and selective increase in conventional and novel protein
kinase C's affinity for phosphatidylserine that is accompanied by
activation and pseudosubstrate release (Fig. 3, top
left)(6) . This high affinity interaction is 1 order of
magnitude stronger for surfaces containing
phosphatidyl-L-serine compared with other acidic lipids such
as phosphatidyl-D-serine (59) . Thus, specific
structural elements of the L-serine headgroup are required for
the high affinity binding of protein kinase C to membranes containing
C1 ligands. Because phosphatidylserine promotes the binding of phorbol
esters to a single recombinant Cys-rich domain(55) , the
specificity may arise from additional interactions of the L-serine headgroup with the C1 domain or with new surfaces
created at the C1-C2 interface. Kinetic studies suggest that protein
kinase C interacts cooperatively with multiple phosphatidylserine
molecules(6, 7) .
The C2 domain
structure provides tantalizing insight into how Ca
Regulation by Phosphorylation in Vivo Pulse-chase experiments by Fabbro and co-workers (72) provided the first evidence that protein kinase C is
phosphorylated in vivo. Specifically, they showed that protein
kinase C is first synthesized as an inactive, dephosphorylated
precursor with an apparent M A
model consistent with biochemical data is presented in the lower
half of Fig. 3. Newly synthesized protein kinase C
associates with a detergent-insoluble cell fraction(72) ; it is
rendered catalytically competent upon phosphorylation by a putative
protein kinase C kinase on its activation loop (Fig. 2C). Negative charge on this loop at the entrance
to the active site correctly aligns residues involved in catalysis in
diverse kinases (11) ; replacement of the phosphorylated
residue (Thr-500) with Glu in protein kinase C Protein kinase C is regulated by two distinct mechanisms: by
phosphorylation which regulates the active site and subcellular
localization of the enzyme, and by second messengers which promote
protein kinase C's membrane association and resulting
pseudosubstrate exposure. Regulation by two independent mechanisms may
provide exquisite fine-tuning for this family of enzymes, ensuring low
basal activity in the midst of complex intracellular signaling
pathways.
Volume 270,
Number 48,
Issue of December 1, 1995 pp. 28495-28498
©1995 by The American Society for Biochemistry and Molecular Biology, Inc.
INTRODUCTION
Structure
Function
Regulation
Pseudosubstrate Regulation
Regulation by Phosphorylation in Vivo
Conclusion
FOOTNOTES
ACKNOWLEDGEMENTS
REFERENCES
for optimal activity (4, 5, 6, 7) . This review discusses
the structure of the protein kinase C family, its enzymatic function,
and how structure and function are regulated by 1) cofactors and 2)
phosphorylation.
-binding site (Fig. 1, yellow) (9) . The C3 and C4 domains form the ATP- and substrate-binding
lobes of the kinase core (Fig. 1, pink and cyan)(11) . The regulatory and catalytic halves are
separated by a hinge region that becomes proteolytically labile when
the enzyme is membrane-bound(6) ; the proteolytically generated
kinase domain (protein kinase M), freed of inhibition by the
pseudosubstrate, is constitutively active (12) .
, two alternatively spliced
variants
I and
II, and . This class distinguishes itself
from the others in that function is regulated by Ca
;
its C2 domain contains a putative Ca
-binding site
(see below). The next well characterized are the novel protein kinase
Cs:
,
,
(L),
, and µ. These isozymes are
structurally similar to the conventional protein kinase Cs, except that
the C2 domain, while maintaining structural residues, does not have the
functional groups that appear to mediate Ca
binding
(see below). The least understood isozymes are the atypical protein
kinase Cs:
and
(I). These differ significantly in structure
from the other two classes; first, the C1 domain contains only one
Cys-rich motif (not two), and second, key residues that maintain the C2
fold do not appear to be present. Furthermore, these isozymes have been
reported not to respond to phorbol esters in vivo or in
vitro(3) . Perhaps adding to the three groups, two kinases
with a C2 domain similar to that of novel protein kinase Cs, but with
no C1 domain, have been identified(13, 14) .
was solved recently with (Fig. 2A) and without bound phorbol ester by Hurley and
co-workers(15) , as was the NMR structure of the corresponding
repeat from protein kinase C
, in the absence of
ligand(16) . Strikingly, this
sheet-rich domain undergoes
no conformational change upon ligand binding. Rather, binding of
phorbol ester plugs the hydrophilic binding site (a groove formed by
two unzipped
strands), so that the top third of the domain
displays a contiguous hydrophobic surface(15) .
with bound phorbol ester (green) based on the
coordinates of Zhang et al.(15) is shown. Conserved
Cys (yellow) and His (purple) that coordinate the two
zinc atoms of each cysteine-rich repeat (78) (green
balls) are indicated. The arrow indicates the C12
position of the phorbol ester that is fatty acylated in bioactive
phorbol esters(51) . B, C2 domain. The ribbon diagram
of residues 167-240 from the C2 domain of synaptotagmin based on
the coordinates of Sutton et al.(17) is shown. The
five aspartates in the Ca
-binding site are indicated
in pink, the bulky hydrophobics on the back face in purple, and the adjacent two
strands that are positively
charged and likely constitute the acidic lipid-binding surface are in blue. Residues shown in orange are conserved in all
C2 domains(9) . C, catalytic (C3 and C4) domain. The
modeled structure of residues 340-632 of protein kinase C
II
with bound pseudosubstrate (residues 9-28) (20) is shown.
The upper lobe, involved primarily in nucleotide binding, is mainly
sheet (pink) and the lower lobe, containing the
substrate-binding cavity, is predominantly
helix (teal
blue). Indicated are ATP (cream), two Mn atoms (red dots), and the pseudosubstrate (green) with the orange dot representing the alanine
at the phosphoacceptor position. The yellow loop at the
entrance to the catalytic site (below ATP) is the activation
loop(11) ; phosphorylation here aligns residues for
catalysis(75) . Reproduced from (20) .
-binding site (pink); on the back face
of this cleft are bulky aromatics (purple) adjacent to a basic
surface formed by two
strands (blue). Sossin and
Schwartz (18) noted that novel protein kinase Cs contain a C2
domain. The solved structure elucidates how these protein kinase Cs can
have this domain without being Ca-regulated; the C2
domain of novel protein kinase Cs has the conserved residues that
maintain the fold of the domain (e.g.Fig. 2B, orange), but the coordinating oxygens in the
Ca
-binding site are mainly absent(9) .
II,
with bound pseudosubstrate, based on the crystal structure of protein
kinase A with bound inhibitory peptide (19) is shown in Fig. 2C(20) . The primary sequence of the
kinase core of conventional protein kinase Cs is approximately 40%
identical to that of protein kinase A's core. The N-terminal
residue of the model is just before the hinge region; the peptide chain
would continue on to the C2 and then C1 domains and then connect to the
pseudosubstrate. Modeling of the latter in the substrate binding cavity
reveals that it is held there, in part, by a cluster of acidic residues
that is unique to the protein kinase C family(20) . The
pseudosubstrate sequence was identified by House and Kemp (10) based on the ability of a synthetic peptide of this
sequence to inhibit protein kinase C.
Enzymology
The chemistry of protein kinase
C's catalytic core is similar to that of the archetypal kinase,
protein kinase A. The kinase uses MgATP as substrate, with a K
for ATP in the low µM range(21) . The enzyme's maximal catalytic rate and K
for a peptide substrate based on its
pseudosubstrate have been reported to be 8 µmol of phosphate
hydrolyzed per min per mg of protein (corresponding to 10 reactions/s)
and 0.2 µM, respectively(10) . This corresponds to
a k/K
of 5 10
sM
, revealing
remarkable efficiency. Most other synthetic peptides have K
values in the low µM range and V
values typically ranging from 1 to 8 µmol
min mg
(22, 23, 24, 25, 26) ,
suggesting that a k
/K
of
10
sM
is
more representative of this family of enzymes. The k
/K
of protein kinase A for
kemptide, a synthetic peptide based on the kinase's consensus
phosphorylation sequence(27) , is comparable(28) .
configurational isomers of a number
of alcohols(24) . Lawrence and co-workers (24) have
suggested that protein kinase C's lack of stereospecificity could
reflect substrate binding in either direction (i.e. C to N or
N to C) in the substrate-binding cavity(24) .
)Biological Function
Given the
plethora of substrates and the effectiveness of phorbol esters in
modulating diverse cellular responses, a multiplicity of functions have
been ascribed to protein kinase C(4) . Recurring themes are
that protein kinase C is involved in receptor desensitization, in
modulating membrane structure events, in regulating transcription, in
mediating immune responses, in regulating cell growth, and in learning
and memory among many other functions. These and the functions of
specific isozymes are described in a number of excellent
reviews(1, 2, 3, 4, 39) .
), non-conventional (e.g. short chained
phosphatidylcholines(45) ), or cofactor-independent substrates (e.g. protamine(46) )(20) . Consistent with
this, incubation of protein kinase C with an antibody directed against
the pseudosubstrate was shown to activate the enzyme, presumably by
removing the pseudosubstrate from the active site(47) .
Diacylglycerol and Phorbol Esters
Since the discovery
that phorbol esters cause protein kinase C to ``translocate''
to membranes (48, 49, 50) , this and the
accompanying activation by these molecules and diacylglycerols have
been the subject of extensive investigations(7, 51) .
Taken together with recent molecular
biological(52, 53, 54, 55, 56) ,
structural(15) , and biophysical
studies(57, 58, 59) , a fairly good
understanding of the mechanism for the effects of these C1 ligands on
protein kinase C function has emerged.
)that is linearly related to the mol fraction C1
ligand in the bilayer, is reversible, and can occur in the absence of
acidic lipids and C2 domain
interactions(
)(55, 57, 58, 59, 60, 61) .
Differences in the biological action of these two classes of ligands
are accounted for by the 2 orders of magnitude increased potency of
phorbol esters compared with diacylglycerol (58) and the long
life of phorbol esters in cells. The phorbol ester domain structure
suggests how the membrane anchor works; by capping the hydrophilic
ligand groove, phorbol ester binding alters the surface hydrophobicity
of the domain, thus promoting the membrane interaction in the absence
of conformational changes(15) . required for the phosphatidylserine-dependent activation of
protein kinase C (64) . The molecular basis for this does not
arise from allosteric interactions between the C1 and C2 domain sites;
Ca
has no effect on protein kinase C's affinity
for either C1 ligand
(59, 65) . Rather, the
apparent synergy between these two activators arises because each, by
separate mechanisms, increases the affinity of protein kinase C for
membranes. Consistent with no allosteric interactions, the structure of
the phorbol ester-binding domain is unchanged by phorbol ester binding (15) .Phosphatidylserine
The requirement for a
``membrane factor'' to activate protein kinase C was
established shortly after the discovery of the enzyme(46) .
Pioneering work by Bell and co-workers in the mid-1980s established the
remarkable specificity for the serine headgroup for
activation(7) . The mechanism for the
phosphatidylserine-dependent stimulation is now well characterized as a
result of binding measurements that have allowed the effect of
phospholipid headgroup structure, diacylglycerol, and Ca on the interaction of protein kinase C with membranes to be
dissected out(6) . Studies with lipid in bilayers or
detergent-lipid mixed micelles have established that the phospholipid
regulation and accompanying conformational changes depend on
phospholipid structure rather than membrane structure(6) ,
although the latter does modulate enzyme
activity(5, 66) .
-regulated for conventional protein
kinase Cs; see next section). This binding is of relatively low
affinity, is sensitive to ionic strength, is accompanied by a
conformational change that exposes the hinge region to proteolysis, and
is typically not accompanied by much activation or pseudosubstrate
exposure (Fig. 3, top
middle)(44, 59, 60) . Note that the
hinge exposure is independent of the active state of the kinase,
reflecting rather the ``membrane-bound conformation'' of the
enzyme (67) .
II); an autophosphorylation at the C terminus (Thr-641 in
II) that stabilizes the catalytically competent
conformation(73) ; and a second autophosphorylation at the C
terminus (Ser-660 in
II) that releases protein kinase C into the
cytosol(73) . This triple phosphorylated mature form is
inactive because the pseudosubstrate occupies the substrate-binding
cavity (middle). Generation of diacylglycerol (DG)
causes the affinity of protein kinase C for membranes to increase
dramatically. Membrane translocation is mediated by diacylglycerol
binding to the C1 domain and phosphatidylserine (PS) binding
to the C2 domain (top right). The affinity for acidic lipids
is increased by Ca for conventional protein kinase
Cs, likely by structuring the lipid-binding surface, but not for novel
protein kinase Cs, whose lipid-binding surface may already be
structured. Protein kinase C can bind to membranes with low affinity
with either C1 domain ligands (not shown) or with C2 domain ligands (top middle). However, it is the high affinity binding (top left) mediated by both domains that results in
pseudosubstrate release and maximal activation. Asterisks indicate the exposed hinge, which becomes proteolytically labile
upon membrane binding (independently of pseudosubstrate
release(67) ), and the exposed pseudosubstrate, which becomes
proteolytically labile upon activation (independently of membrane
binding(20) ).
Calcium Ions
Ca increases the
affinity of conventional protein kinase Cs for negatively charged
lipids(69) , with no selectivity for headgroup other than the
requirement for negative charge(59) . This increase varies
linearly with Ca
concentration in the low µM to submillimolar range(65) , consistent with the single
Ca
-binding site apparent in the C2 domain
structure(17) . The dissociation constant of Ca
from membrane-bound protein kinase C has been calculated to be
approximately 700 nM, and that from soluble protein kinase C
has been estimated to be 3 mM(65) .
might increase the affinity of conventional, but not novel,
protein kinase Cs for acidic lipids. For conventional protein kinase
Cs, binding of Ca
to the aspartate-lined
``mouth'' (Fig. 2B) might clamp together the
upper and lower lobes, thus orienting the bulky aromatics on the back
face of the mouth to interact with the membrane and orienting the basic
face of the
sheet behind the site to interact with lipid
headgroups. For novel protein kinase Cs (such as ), the presence
of an Arg instead of an Asp at one of the positions in the site (9) might cause the mouth to adopt the closed conformation, so
that the domain is already structured to bind acidic lipids. C1 ligands
would then target novel protein kinase Cs to membranes, with the
reduction in dimensionality promoting the binding of the C2 domain to
acidic lipids. Consistent with this, the lipid regulation of novel
protein kinase Cs is the same as that for conventional protein kinase
Cs, except that it occurs in the absence of
Ca
(70) .
Substrates
Protein kinase C phosphorylates a
number of Arg-rich proteins in a cofactor-independent
manner(46, 71) . These substrates, alone, are able to
displace the pseudosubstrate from the kinase core(20) . One
possibility is that these Arg-rich peptides neutralize the acidic patch
that appears to maintain the pseudosubstrate in the active
site(20) , thus releasing the basic pseudosubstrate by
competing for contacts. In this regard, the ability of Arg-rich
peptides to promote protein kinase C autophosphorylation (rather than
compete with it) led to the suggestion that Arg-rich molecules bind to
a separate site from the active site(71) . An intriguing
possibility is that the acidic cluster interacts with Arg-rich
sequences of cytoskeletal proteins, thus allowing activation distal
from the lipid bilayer.
of 74 kDa; this was
chased to a transient 77-kDa phospho-form and then to the final 80-kDa
mature form. Mass spectrometry has recently revealed that protein
kinase C is modified by three phosphorylations in vivo (73,
74). The differential dephosphorylation of these sites by protein
phosphatases 1 and 2A(75) , as well as analysis of
phosphorylation site mutants(76, 77) , has allowed the
function of each phosphorylation to be identified (73) .
II results in
activatable enzyme (77) whereas replacement with neutral
non-phosphorylatable residues in this isozyme (77) or protein
kinase C
(76) results in kinase that cannot be activated.
The first consequence of the transphosphorylation appears to be
autophosphorylation at the C terminus of the kinase; this residue is
Thr-641 in protein kinase C
II (9 residues removed from the C
terminus of the model in Fig. 2C)(73, 74) . Phosphorylation
here likely stabilizes the catalytically competent conformation of the
kinase as it replaces the requirement for negative charge at the
activation loop(73) ; this phosphorylation causes the first
detectable shift in electrophoretic mobility(73, 75) .
Last, the enzyme autophosphorylates further along the C terminus
(Ser-660 in protein kinase C
II) in a motif shared by several
other kinases(73) ; this phosphorylation causes the final shift
in electrophoretic mobility and releases the mature enzyme into the
cytosol(73, 75) . It is this 80-kDa form, localized to
the detergent-soluble fraction, that has been extensively purified and
studied in vitro. Curiously, it is only half-phosphorylated at
the activation loop (but quantitatively phosphorylated at the two
C-terminal sites)(73) , suggesting that
dephosphorylation/transphosphorylation at this position may regulate
the kinase in response to stimuli. The mature form then translocates to
the membrane and undergoes the pseudosubstrate regulation discussed
above.
)
) 10
mol % relative to
membrane lipids; that for diacylglycerol is 250 times higher (M. Mosior
and A. C. Newton, Biochemistry, in press).
)
I thank members of my laboratory for critically
reading this manuscript and for many helpful discussions.
©1995 by The American Society for Biochemistry and Molecular Biology, Inc.
![]()
CiteULike
Complore
Connotea
Del.icio.us
Digg
Reddit
Technorati What's this?
This article has been cited by other articles:
![]() |
C. A. Farah, I. Nagakura, D. Weatherill, X. Fan, and W. S. Sossin Physiological Role for Phosphatidic Acid in the Translocation of the Novel Protein Kinase C Apl II in Aplysia Neurons Mol. Cell. Biol., August 1, 2008; 28(15): 4719 - 4733. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. Liao, Y. Zhang, and M. L. Dufau Protein Kinase C{alpha}-Induced Derepression of the Human Luteinizing Hormone Receptor Gene Transcription through ERK-Mediated Release of HDAC1/Sin3A Repressor Complex from Sp1 Sites Mol. Endocrinol., June 1, 2008; 22(6): 1449 - 1463. [Abstract] [Full Text] [PDF] |
||||
![]() |
B. Mellstrom, M. Savignac, R. Gomez-Villafuertes, and J. R. Naranjo Ca2+-Operated Transcriptional Networks: Molecular Mechanisms and In Vivo Models Physiol Rev, April 1, 2008; 88(2): 421 - 449. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. Serova, A. Ghoul, K. A. Benhadji, S. Faivre, C. Le Tourneau, E. Cvitkovic, F. Lokiec, J. Lord, S. M. Ogbourne, F. Calvo, et al. Effects of protein kinase C modulation by PEP005, a novel ingenol angelate, on mitogen-activated protein kinase and phosphatidylinositol 3-kinase signaling in cancer cells Mol. Cancer Ther., April 1, 2008; 7(4): 915 - 922. [Abstract] [Full Text] [PDF] |
||||
![]() |
D. R. Dries and A. C. Newton Kinetic Analysis of the Interaction of the C1 Domain of Protein Kinase C with Lipid Membranes by Stopped-flow Spectroscopy J. Biol. Chem., March 21, 2008; 283(12): 7885 - 7893. [Abstract] [Full Text] [PDF] |
||||
![]() |
W. Bakker, P. Sipkema, C. D.A. Stehouwer, E. H. Serne, Y. M. Smulders, V. W.M. van Hinsbergh, and E. C. Eringa Protein Kinase C {theta} Activation Induces Insulin-Mediated Constriction of Muscle Resistance Arteries Diabetes, March 1, 2008; 57(3): 706 - 713. [Abstract] [Full Text] [PDF] |
||||
![]() |
R. D. Ramnath, J. Sun, S. Adhikari, L. Zhi, and M. Bhatia Role of PKC-{delta} on substance P-induced chemokine synthesis in pancreatic acinar cells Am J Physiol Cell Physiol, March 1, 2008; 294(3): C683 - C692. [Abstract] [Full Text] [PDF] |
||||
![]() |
V. Casciani, E. Marinoni, A. D. Bocking, M. Moscarini, R. Di Iorio, and J. R. G. Challis Opposite Effect of Phorbol Ester PMA on PTGS2 and PGDH mRNA Expression in Human Chorion Trophoblast Cells Reproductive Sciences, January 1, 2008; 15(1): 40 - 50. [Abstract] [PDF] |
||||
![]() |
T. J. Jerde, W. S. Mellon, D. E. Bjorling, C. M. Checura, K. Owusu-Ofori, J. J. Parrish, and S. Y. Nakada Stretch Induction of Cyclooxygenase-2 Expression in Human Urothelial Cells Is Calcium- and Protein Kinase C {zeta}-Dependent Mol. Pharmacol., January 1, 2008; 73(1): 18 - 26. [Abstract] [Full Text] [PDF] |
||||
![]() |
V. Aires, A. Hichami, R. Filomenko, A. Ple, C. Rebe, A. Bettaieb, and N. A. Khan Docosahexaenoic Acid Induces Increases in [Ca2+]i via Inositol 1,4,5-Triphosphate Production and Activates Protein Kinase C{gamma} and -{delta} via Phosphatidylserine Binding Site: Implication in Apoptosis in U937 Cells Mol. Pharmacol., December 1, 2007; 72(6): 1545 - 1556. [Abstract] [Full Text] [PDF] |
||||
![]() |
D. White, E. de Lamirande, and C. Gagnon Protein kinase C is an important signaling mediator associated with motility of intact sea urchin spermatozoa J. Exp. Biol., November 15, 2007; 210(22): 4053 - 4064. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. Amos, M. Mut, C. G. diPierro, J. E. Carpenter, A. Xiao, Z. A. Kohutek, G. T. Redpath, Y. Zhao, J. Wang, M. E. Shaffrey, et al. Protein Kinase C-{alpha} Mediated Regulation of Low-Density Lipoprotein Receptor Related Protein and Urokinase Increases Astrocytoma Invasion Cancer Res., November 1, 2007; 67(21): 10241 - 10251. [Abstract] [Full Text] [PDF] |
||||
![]() |
R. Alzamora, L. R. Brown, and B. J. Harvey Direct Binding and Activation of Protein Kinase C Isoforms by Aldosterone and 17{beta}-Estradiol Mol. Endocrinol., November 1, 2007; 21(11): 2637 - 2650. [Abstract] [Full Text] [PDF] |
||||
![]() |
R. A. Fenton and M. A. Knepper Mouse Models and the Urinary Concentrating Mechanism in the New Millennium Physiol Rev, October 1, 2007; 87(4): 1083 - 1112. [Abstract] [Full Text] [PDF] |
||||
![]() |
N. M. Mhaidat, R. F. Thorne, X. D. Zhang, and P. Hersey Regulation of Docetaxel-Induced Apoptosis of Human Melanoma Cells by Different Isoforms of Protein Kinase C Mol. Cancer Res., October 1, 2007; 5(10): 1073 - 1081. [Abstract] [Full Text] [PDF] |
||||
![]() |
W. Shi, N. Cui, Y. Shi, X. Zhang, Y. Yang, and C. Jiang Arginine vasopressin inhibits Kir6.1/SUR2B channel and constricts the mesenteric artery via V1a receptor and protein kinase C Am J Physiol Regulatory Integrative Comp Physiol, |