Decrase Actin Stress Fibers Foca
Adheaions
Mech Ageing Dev. 2006 Mar 1; [Epub
ahead of print] Biochemistry.
2006 Jan 17;45(2):381-90. mTOR/RICTOR is the Ser473 kinase
for Akt/PKB in 3T3-L1 adipocytes. Lycopene induces apoptosis in immortalized fibroblasts
exposed to tobacco smoke condensate through arresting cell cycle and
down-regulating cyclin D1, pAKT
and pBad. conclude
mTOR complexed to
RICTOR is the Ser473 kinase in 3T3-L1 adipocytes. Ovarian follicle development is dependent
on growth factors that stimulate cell proliferation and act as survival
factors to prevent apoptosis of follicle cells. We examined the mechanism
of the protective effect of IGF-I against Fas ligand (FasL)-induced
apoptosis of granulosa cells and its relationship
to cell proliferation. IGF-I activated both the phosphoinositide
3'-OH kinase (PI3K) and the mitogen-activated
protein kinase (MAPK) pathways. Experiments using
specific inhibitors of these pathways showed that protection by IGF-I was
mediated by the PI3K pathway and not the MAPK pathway. Recombinant
adenoviruses were used to test whether the downstream target of PI3K
activation, Akt kinase,
was required for protection against apoptosis. Expression of dominant
negative Akt (dnAkt)
prevented protection by IGF-I while expression of constitutively active Akt (myrAkt) mimicked the
effect of IGF-I. Treatment with IGF-I, or expression of myrAkt,
increased progression from G0/G1 to S phase of the cell cycle while
expression of dnAkt inhibited G0/G1 to S phase
progression and prevented the stimulatory effect of IGF-I. We tested
whether cell cycle progression was required for protection from apoptosis
using the cyclin dependent kinase-2 inhibitor roscovitine, which blocks cells at the G1/S transition.
Roscovitine prevented the protective effect of
IGF-I and myrAkt expression against apoptosis.
Therefore, activation of Akt is not sufficient to
protect granulosa cells from apoptosis in the
absence of cell cycle progression. In summary, IGF-I protects granulosa cells from apoptosis by activation of the
PI3K/Akt pathway. This protective effect can only occur when progression
from G1 to S phase of the cell cycle regulated by the PI3K/Akt pathway is
unperturbed
Tumor necrosis factor-alpha-308A/G
polymorphism is associated with age at onset of Alzheimer's disease.
Lio
D, Annoni
G, Licastro
F, Crivello
A, Forte GI, Scola
L, Colonna-Romano G,
Candore
G, Arosio
B, Galimberti
L, Vergani
C, Caruso C.
Gruppo di Studio sull'Immunosenescenza, Dipartimento
di Biopatologia e Metodologie, Biomediche, Universita di Palermo, Corso Tukory 211, 90134
Palermo, Italy.
Pro-inflammatory cytokines and acute-phase proteins play an important role
in Alzheimer's disease (AD) neurodegeneration,
and common polymorphisms of genes controlling their production have been
shown to be associated with AD. Tumor necrosis factor (TNF)-alpha is an
inflammatory cytokine involved in the local immune response occurring in
the central nervous system of AD patients. Genetic variation could
contribute to the risk of developing AD or influence the age at the onset
of the disease. We genotyped 222 patients (152 women, 70
men; age range 60-87) and 240 non-demented age-matched healthy controls for
TNF-alpha -308 G/A single nucleotide polymorphism (SNP). No significant
differences were observed in genotyped frequencies between patients and
controls, whereas carriers of -308A showed a significantly lower mean age
at onset than non-carriers of this allele. This difference was more evident
taking into account ApolipoproteinE (ApoE) status since the lowest age at onset was observed
in patients carrying the -308ATNF+/APOE4+ genotypes. In conclusion, our
data support previous suggestions that, at least in Caucasians, the TNF
gene is a disease modifier gene in patients in which AD is rising, bringing
to light the importance of genetic variation at the pro-inflammatory
components in the progression of AD.
Self-assembly of HEK
cell-secreted ApoE particles resembles ApoE enrichment of lipoproteins as a ligand for the LDL receptor-related protein.
LaDu
MJ, Stine WB Jr, Narita M, Getz GS, Reardon CA,
Bu G.
Department of Anatomy and Cell Biology,
Recent studies have shown that the lipidation and
assembly state of apolipoprotein E (apoE) determine receptor recognition and amyloid-beta peptide (Abeta)
binding. We previously demonstrated that apoE
secreted by HEK cells stably expressing apoE3 or apoE4 (HEK-apoE) binds Abeta and
inhibits Abeta-induced neurotoxicity
by an isoform-specific process that requires apoE receptors. Here we characterized the structure of
HEK-apoE assemblies and determined their receptor
binding specificity. By chromatography, HEK-apoE
elutes in high molecular mass fractions and is the size of plasma HDL,
consistent with a multiprotein assembly. No lipid
was associated with these apoE assemblies.
Several methods for analyzing receptor binding indicate that HEK-apoE is a ligand for
low-density lipoprotein (LDL) receptor-related protein (LRP) but not the
LDL receptor. This suggests that self-assembly of apoE
may induce a functional conformation necessary for binding to LRP. Our
results indicate that, in addition to lipid content, the assembly state of apoE influences Abeta binding
and receptor recognition.
PMID: 16401069 [PubMed - in process]
Hresko
RC, Mueckler
M.
Department of Cell Biology and Physiology, Washington University, School of
Medicine, St. Louis, MO 63110-1093.
The insulin-signaling pathway leading to the activation of Akt/PKB has been well-characterized except for a single
step, the phosphorylation of Akt
at Ser473. Double-stranded DNA-dependent protein kinase (DNA-PK). ataxia
telangiectasia mutated (ATM) gene product, Integrin-linked kinase (ILK),
Protein Kinase Ca (PKCa),
and mammalian target of Rapamycin (mTOR) when complexed to rapamycin insensitive companion of mTOR
(RICTOR) have all been identified as playing a critical role in Akt-Ser473 phosphorylation. However, the apparently disparate
results reported in these studies are difficult to evaluate, given that
different stimuli and cell types were examined and that all of the
candidate proteins have never been systematically studied in a single
system. Additionally, none of these studies were performed in a classical
insulin-responsive cell-type or tissue such as muscle or fat. We therefore
examined each of these candidates in 3T3-L1 adipocytes.
In vitro kinase assays, using different subcellular fractions of 3T3-L1 adipocytes,
revealed that phosphatidylinositol 3,4,5-trisphosphate (PIP3)-stimulated Ser473 phosphorylation correlated well with the amount of DNA-PK,
mTOR, and RICTOR but did not correlate with
levels of ATM, ILK, and PKCa. PKCa
was completely absent from compartments with Ser473 phosphorylation
activity. Although purified DNA-PK could phosphorylate
a peptide derived from Akt that contains amino acid
Ser473, it could not phosphorylate full-length
Akt2. Vesicles immunoprecipitated from
low-density microsomes (LDM) using antibodies
directed against mTOR or RICTOR had
PIP3-stimulated Ser473 activity that was sensitive to wortmannin
but not staurosporine. In contrast, immunopurified LDM vesicles containing ILK could not phosphorylate Akt on Ser473
in vitro. Small interference RNA (siRNA)-knockdown
of RICTOR, but not DNA-PK, ATM, or ILK, suppressed insulin-activated Ser473
phosphorylation and to a lesser extent Thr308 phosphorylation in 3T3-L1 adipocytes.
Based on our cell-free kinase and siRNA results, we conclude mTOR
complexed to RICTOR is the Ser473 kinase in 3T3-L1 adipocytes.
Palozza
P, Sheriff A,
Serini
S, Boninsegna
A, Maggiano
N, Ranelletti
FO, Calviello
G, Cittadini
A.
There is a lot of interest in the health benefits of dietary carotenoids and on the relationship of these compounds
with smoke. In particular, it is unknown if the enhanced cancer risk
observed in smokers following beta-carotene supplementation can be also
found using other carotenoids. Here, we studied
the effects of the tomato carotenoid lycopene on molecular pathways involved in cell cycle
progression, apoptosis and survival in immortalized RAT-1 fibroblasts
exposed to cigarette smoke condensate (TAR). Lycopene
(0.5-2.0 muM) inhibited cell growth in a dose-and
time-dependent manner, by arresting cell cycle progression and by promoting
apoptosis in cells exposed to TAR. The arrest of cell cycle was independent
of p53 and of 8-OH-dG DNA damage and related to a decreased expression of cyclin D1. Moreover, the carotenoid
up-regulated apoptosis and down-regulated the phosphorylation
of AKT and Bad in cells exposed to TAR. Such an effect was associated to an
inhibition of TAR-induced expression of Cox-2 and hsp90, which is known to
maintain AKT activity. This study suggests that lycopene,
differently from beta-carotene, can exert protective effects against
cigarette smoke condensate.
PMID: 16215689 [PubMed - as supplied
PMID: 16221682 [PubMed - as supplied by
publisher]