Alzheimer's disease
Drug Abuse
Parkinson's disease
Cell
Mol Life Sci. 2005 Mar;62(5):606-18. J
Pharmacol Exp Ther.
2005 Nov;315(2):872-8. Epub
2005 Jul 22. Nucleic
Acids Res. 2006 Mar 20;34(5):1620-32. Print
2006. Diabetes.
2006 Apr;55(4):1022-8.
A second protein kinase
CK1-mediated step negatively regulates Wnt signalling by disrupting the lymphocyte enhancer
factor-1/beta-catenin complex.
Hammerlein A, Weiske J, Huber
O.
ABDA - Federal
Deregulated activation of the canonical Wnt signalling pathway leads to stabilization of beta-catenin and is critically involved in carcinogenesis by
an inappropriate induction of lymphocyte enhancer factor (LEF-1)/beta-catenin-dependent transcription of Wnt
target genes. Phosphorylation of the pathway
components beta-catenin, Dishevelled,
Axin and APC (adenomatous
polyposis coli) by glycogen synthase
kinase-3beta, CK1 and CK2 is of central importance in the regulation of the
beta-catenin destruction complex. Here, we
identify CK1 and CK2 as major kinases that
directly bind to and phosphorylate LEF-1 inducing
distinct, kinase-specific changes in the
LEF-1/DNA complex. Moreover, CK1-dependent phosphorylation
in contrast to CK2 disrupts the association of beta-catenin
and LEF-1 but does not impair DNA binding of LEF-1. Sequential phosphorylation assays revealed that for efficient
disruption of the LEF-1/beta-catenin complex, beta-catenin
also has to be phosphorylated. Consistent with
these observations, CK1-dependent phosphorylation
inhibits, whereas CK2 activates LEF-1/beta-catenin transcriptional activity
in reporter gene assays. These data are in line with a negative regulatory
function of CK1 in the Wnt signalling
pathway, where CK1 in addition to the beta-catenin
destruction complex at a second level acts as a negative regulator of the
LEF-1/beta-catenin transcription complex, thereby protecting cells from
development of cancer.
PMID: 15747065 [PubMed - indexed for MEDLINE]
Nicotine regulates DARPP-32 (dopamine- and cAMP-regulated phosphoprotein
of 32 kDa) phosphorylation
at multiple sites in neostriatal neurons.
Hamada
M, Hendrick JP, Ryan
GR, Kuroiwa M, Higashi
H, Tanaka
M, Nairn AC, Greengard P, Nishi
A.
Department of Pharmacology,
Nicotinic acetylcholine receptors (nAChRs)
regulate dopaminergic signaling in the striatum
by modulating the release of neurotransmitters. We have recently reported
that nicotine stimulates the release of dopamine via alpha4beta2(*)
nAChRs and/or alpha7 nAChRs,
leading to the regulation of DARPP-32 at Thr34, the site involved in
regulation of protein phosphatase-1 (PP-1). In this study, we investigated
the regulation of DARPP-32 phosphorylation at its
other sites, Thr75 [cyclin-dependent kinase-5
(Cdk5) site], Ser97 (CK2 site), and Ser130 (CK1 site), that serve to
modulate Thr34 phosphorylation and dephosphorylation. In neostriatal
slices, nicotine (100 microM) increased phosphorylation of DARPP-32 at Ser97 and Ser130 at an
early time point (30 s) and decreased phosphorylation
of DARPP-32 at Thr75 at a late time point (3 min). The increase in Ser97
and Ser130 phosphorylation was mediated through
the release of dopamine via activation of alpha4beta2(*)
nAChRs and alpha7 nAChRs
and the subsequent activation of dopamine D1 and D2 receptors. The decrease
in Thr75 phosphorylation was mediated through the
release of dopamine via activation of alpha4beta2(*)
nAChRs and the subsequent activation of dopamine
D1 receptors. These various actions of nicotine on modulatory
sites of phosphorylation would be predicted to
result in a synergistic increase in the state of phosphorylation
of DARPP-32 at Thr34 and thus would contribute to increased dopamine D1
receptor/DARPP-32 Thr34/PP-1 signaling.
PMID: 16040813 [PubMed - indexed for MEDLINE]
Dimerization and opposite base-dependent catalytic
impairment of polymorphic S326C OGG1 glycosylase.
Hill
JW, Evans
MK.
Laboratory of Cellular and Molecular Biology, National
Institute on Aging, National Institutes of Health,
Human 8-oxoguanine-DNA glycosylase (OGG1) is the
major enzyme for repairing 8-oxoguanine (8-oxoG), a mutagenic guanine base
lesion produced by reactive oxygen species (ROS). A frequently occurring
OGG1 polymorphism in human populations results in the substitution of
serine 326 for cysteine (S326C). The 326 C/C
genotype is linked to numerous cancers, although the mechanism of
carcinogenesis associated with the variant is unclear. We performed
detailed enzymatic studies of polymorphic OGG1 and found functional defects
in the enzyme. S326C OGG1 excised 8-oxoG from duplex DNA and cleaved abasic sites at rates 2- to 6-fold lower than the
wild-type enzyme, depending upon the base opposite the lesion. Binding
experiments showed that the polymorphic OGG1 binds DNA damage with
significantly less affinity than the wild-type enzyme. Remarkably, gel
shift, chemical cross-linking and gel filtration experiments showed that
S326C both exists in solution and binds damaged DNA as a dimer. S326C OGG1 enzyme expressed in human cells was
also found to have reduced activity and a dimeric
conformation. The glycosylase activity of S326C
OGG1 was not significantly stimulated by the presence of AP-endonuclease. The altered substrate specificity, lack
of stimulation by AP-endonuclease 1 (APE1) and
anomalous DNA binding conformation of S326C OGG1 may contribute to its
linkage to cancer incidence.
PMID: 16549874 [PubMed - indexed for MEDLINE]
Protection of INS-1 cells from free fatty
acid-induced apoptosis by targeting hOGG1 to mitochondria.
Rachek
LI, Thornley
NP, Grishko
VI, LeDoux
SP, Wilson
GL.
Department of Cell Biology and Neuroscience, College of Medicine,
University of South Alabama, Mobile, AL 36688, USA.
lrachek@jaguar1.usouthal.edu
Chronic exposure to elevated levels of free fatty
acids (FFAs) impairs pancreatic beta-cell
function and contributes to the decline of insulin secretion in type 2
diabetes. Previously, we reported that FFAs
caused increased nitric oxide (NO) production, which damaged mitochondrial
DNA (mtDNA) and ultimately led to apoptosis in
INS-1 cells. To firmly establish the link between FFA-generated mtDNA damage and apoptosis, we stably transfected INS-1 cells with an expression vector
containing the gene for the DNA repair enzyme human 8-oxoguanine DNA glycosylase/apurinic lyase
(hOGG1) downstream of the mitochondrial targeting sequence (MTS) from
manganese superoxide dismutase.
Successful integration of MTS-OGG1 into the INS-1 cellular genome was
confirmed by Southern blot analysis. Western blots and enzyme activity
assays revealed that hOGG1 was targeted to mitochondria and the recombinant
enzyme was active. MTS-OGG1 cells showed a significant decrease in
FFA-induced mtDNA damage compared with
vector-only transfectants. Additionally, hOGG1 overexpression in mitochondria decreased FFA-induced
inhibition of ATP production and protected INS-1 cells from apoptosis.
These results indicate that mtDNA damage plays a
pivotal role in FFA-induced beta-cell dysfunction and apoptosis. Therefore,
targeting DNA repair enzymes into beta-cell mitochondria could be a
potential therapeutic strategy for preventing or delaying the onset of type
2 diabetes symptoms.
PMID: 16567524 [PubMed - in process]
Wnt signalling