32 research outputs found
Release of extracellular membrane vesicles from microvilli of epithelial cells is enhanced by depleting membrane cholesterol
AbstractWe previously reported on the occurrence of prominin-1-carrying membrane vesicles that are released into body fluids from microvilli of epithelial cells. This release has been implicated in cell differentiation. Here we have characterized these vesicles released from the differentiated Caco-2 cells. We find that in these vesicles, prominin-1 directly interacts with membrane cholesterol and is associated with a membrane microdomain. The cholesterol depletion using methyl-β-cyclodextrin resulted in a marked increase in their release, and a dramatic change in the microvillar ultrastructure from a tubular shape to a “pearling” state, with multiple membrane constrictions, suggesting a role of membrane cholesterol in vesicle release from microvilli
A complex secretory program orchestrated by the inflammasome controls paracrine senescence
Oncogene-induced senescence (OIS) is crucial for tumour suppression. Senescent cells implement a complex pro-inflammatory response termed the senescence-associated secretory phenotype (SASP). The SASP reinforces senescence, activates immune surveillance and paradoxically also has pro-tumorigenic properties. Here, we present evidence that the SASP can also induce paracrine senescence in normal cells both in culture and in human and mouse models of OIS in vivo. Coupling quantitative proteomics with small-molecule screens, we identified multiple SASP components mediating paracrine senescence, including TGF-β family ligands, VEGF, CCL2 and CCL20. Amongst them, TGF-β ligands play a major role by regulating p15INK4b and p21CIP1. Expression of the SASP is controlled by inflammasome-mediated IL-1 signalling. The inflammasome and IL-1 signalling are activated in senescent cells and IL-1α expression can reproduce SASP activation, resulting in senescence. Our results demonstrate that the SASP can cause paracrine senescence and impact on tumour suppression and senescence in vivo
The role of circadian rhythms in epidermal homeostasis
The
natural
daily
cycles
of
light
and
dark
have
played
a
fundamental
role
in
shaping
the
development
of
an
adaptive
intrinsic
clock
mechanism
which
allows
organisms
to
coordinate
the
function
of
multiple
organs
by
setting
the
correct
circadian
timing
of
cellular
processes
ensuring
proper
homeostasis.
In
mammalian
skin,
homeostasis
is
maintained
by
epidermal
stem
cells
(epSCs).
EpSCs
localize
to
specialized
niches
where
they
undergo
cycles
of
quiescence
and
proliferation.
Several
pathways
are
known
to
play
essential
roles
in
epSC
function;
however,
how
are
these
pathways
spatiotemporally
coordinated,
and
why
not
all
stem
cells
within
the
niche
behave
in
the
same
manner,
is
still
poorly
understood.
We
have
analyzed
the
role
of
the
molecular
circadian
clock
in
fine-‐tuning
the
behavior
of
epidermal
stem
cells.
Using
a
fluorescent
circadian
reporter
mouse
model,
we
demonstrate
that
the
dormant
epidermal
stem
cell
compartment
contains
two
co-‐existing
populations
of
stem
cells
in
different
clock
states.
Global
comparative
transcriptome
analysis
indicated
that
each
clock
population
corresponds
to
a
distinct
predisposition
state
of
response
towards
stem
cell
activating
and
dormancy
cues.
We
provide
evidence
that
the
core
circadian
transcription
factors
BMAL1
and
CLOCK
bind
to
regulatory
elements
in
the
promoters
of
several
of
these
stem
cell
homeostatic
genes,
thus
being
directly
responsible
for
creating
these
two
stem
cell
clock
states.
Unbalancing
this
clock
driven
equilibrium
of
epSCs
in
vivo
resulted
in
progressive
changes
in
the
response
of
stem
cells
to
activating
or
dormancy
cues,
which
led
to
a
progressive
premature
tissue
aging,
and
a
significant
reduction
in
the
development
of
cutaneous
squamous
cell
carcinomas.
Thus,
our
results
indicate
that
the
molecular
clock
machinery
fine-‐tunes
the
spatiotemporal
behavior
of
epidermal
stem cells
within
their
niche,
and
that
perturbation
of
this
mechanism
affects
tissue
homeostasis
and
the
predisposition
to
neoplastic
transformation.Los
ciclos
naturales
de
luz
y
oscuridad
han
sido
determinantes
en
el
desarrollo
de
un
reloj
molecular
intrínseco
que
permite
coordinar
la
función
de
múltiples
órganos
para
mantener
la
homeostasis
global
del
organismo.
La
homeostasis
del
compartimento
queratinocítico
de
la
piel
depende
de
una
población
de
células
troncales
adultas
epidermales
(epSCs).
Las
epSCs
están
localizadas
en
nichos
específicos
y
especializados
desde
dónde
responden
a
las
necesidades
de
repoblación
celular
del
tejido
mediante
la
alternancia
de
fases
de
quiescencia
y
proliferación.
Varias
rutas
de
señalización
regulan
el
comportamiento
de
las
epSCs;
sin
embargo,
aún
no
entendemos
bien
porqué
no
todas
las
epSCs
se
comportan
de
la
misma
manera
dentro
de
un
mismo
nicho
troncal,
y
cómo
están
coordinadas
a
nivel
espacio-‐temporal.
Hemos
analizado
el
impacto
del
ritmo
circadiano
sobre
las
función
de
las
epSCs.
Mediante
un
ratón
reportero
fluorescente
del
ritmo
circadiano
hemos
demostrado
que
el
nicho
troncal
quiescente
contiene
dos
poblaciones
de
epSCs
en
diferentes
fases
de
su
reloj
molecular.
El
análisis
comparativo
global
del
transcriptoma
de
ambas
poblaciones
indicó
que
las
dos
poblaciones
corresponden
a
dos
estados
opuestos
de
predisposición
a
responder
a
estímulos
de
activación
y
quiescencia.
Mostramos
resultados
que
demuestran
que
los
factores
de
transcripción
circadianos
Bmal1
y
Clock
regulan
directamente
la
expresión
de
genes
que
regulan
el
comportamiento
de
las
epSCs.
La
arritmia
in
vivo
en
las
epSCs
resultó
en
una
pérdida
progresiva
de
la
homeostasis
tisular,
un
envejecimiento
prematuro
y
una
reducción
significativa
en
el
desarrollo
de
tumores
escamosos
de
piel.
Por
lo
tanto,
nuestros
resultados
indican
que
la
maquinaria
del
reloj
molecular
permite
a
las
epSCs
a
anticiparse
y
coordinar
su respuesta
a
estímulos
locales
del
nicho,
lo
que
constituye
un
mecanismo
esencial
para
su
correcta
función
en
el
tejid
GM1 and GM3 gangliosides highlight distinct lipid microdomains within the apical domain of epithelial cells
AbstractThe apical domain of epithelial cells is composed of distinct subdomains such as microvilli, primary cilia and a non-protruding region. Using the cholesterol-binding protein prominin-1 as a specific marker of plasma membrane protrusions we have previously proposed the co-existence of different cholesterol-based lipid microdomains (lipid rafts) within the apical domain [Röper, K., Corbeil, D. and Huttner, W.B. (2000), Retention of prominin in microvilli reveals distinct cholesterol-based lipid microdomains in the apical plasma membrane. Nat. Cell Biol. 2, 582–592]. To substantiate the hypothesis that the microvillar plasma membrane subdomains contain a distinct set of lipids compared to the planar portion we have investigated the distribution of prominin-1 and two raft-associated gangliosides GM1 and GM3 by fluorescence microscopy. GM1 was found to co-localize with prominin-1 on microvilli whereas GM3 was segregated from there suggesting its localization in the planar region. Regarding the primary cilium, overlapping fluorescent signals of GM1 or GM3 and prominin-1 were observed. Thus, our data demonstrate that specific ganglioside-enriched rafts are found in different apical subdomains and reveal that two plasma membrane protrusions with different structural bases (actin for the microvillus and tubulin for the cilium) are composed of distinct types of lipid
Analyzing the temporal regulation of translation efficiency in mouse liver
Mammalian physiology and behavior follow daily rhythms that are orchestrated by endogenous timekeepers known as circadian clocks. Rhythms in transcription are considered the main mechanism to engender rhythmic gene expression, but important roles for posttranscriptional mechanisms have recently emerged as well (reviewed in Lim and Allada (2013) [1]). We have recently reported on the use of ribosome profiling (RPF-seq), a method based on the high-throughput sequencing of ribosome protected mRNA fragments, to explore the temporal regulation of translation efficiency (Janich et al., 2015 [2]). Through the comparison of around-the-clock RPF-seq and matching RNA-seq data we were able to identify 150 genes, involved in ribosome biogenesis, iron metabolism and other pathways, whose rhythmicity is generated entirely at the level of protein synthesis. The temporal transcriptome and translatome data sets from this study have been deposited in NCBI's Gene Expression Omnibus under the accession number GSE67305. Here we provide additional information on the experimental setup and on important optimization steps pertaining to the ribosome profiling technique in mouse liver and to data analysis
Expression Analysis of the Stem Cell Marker <i>Pw1/Peg3</i> Reveals a CD34 Negative Progenitor Population in the Hair Follicle
International audiencePw1/Peg3 is a parentally imprinted gene expressed in adult stem cells in every tissue thus far examined including the stem cells of the hair follicle. Using a Pw1/Peg3 reporter mouse, we carried out a detailed dissection of the stem cells in the bulge, which is a major stem cell compartment of the hair follicle in mammalian skin. We observed that PW1/Peg3 expression initiates upon placode formation during fetal development, coincident with the establishment of the bulge stem cells. In the adult, we observed that PW1/Peg3 expression is found in both CD34+ and CD34- populations of bulge stem cells. We demonstrate that both populations can give rise to new hair follicles, reconstitute their niche, and self-renew. These results demonstrate that PW1/Peg3 is a reliable marker of the full population of follicle stem cells and reveal a novel CD34- bulge stem-cell population. Stem Cells 2017;35:1015–102
Additional file 7: of Translational contributions to tissue specificity in rhythmic and constitutive gene expression
Expression plots for kidney and liver for the 178 common rhythmic genes of Fig. 3c. (ZIP 3338.28 kb