 |
|||||||||||||||||
|
|||||||||||||||||
|
|||||||||||||||||
 |
|
|
|
|
|||||||||||||
|
Faculty
of 1000 Biology - Reviews
|
||||||||||||||||
|
|
|
|||||||||||||||
 |
128. Wei, S.H.,
H. Rosen, M.P. Matheu, M.G. Sanna, S-K. Wang, E. Jo, C-H Wong, I.
Parker, and M.D. Cahalan. 2005.
|
 |
|||||||||||||||
Evaluated 12 Jan 2006 |
This
is an elegant and thought-provoking paper that proposes a novel model
for sphingosine-1 phosphate receptor (S1P1)-mediated inhibition of
T cell egress in lymphoid tissue. Imaging of T cells
in explanted lymph nodes after treatment with S1P1 agonists revealed
a marked reduction of T cell migration in the lymph node medulla.
This could be reversed by washout of the S1P1 agonist or addition
of S1P1 antagonists, such that medullar migration and sinus entry
was restored. The authors interpret their data as evidence for the
existence of endothelial gates (which are closed by S1P1 agonists)
through which lymphocytes pass. This work does not provide definitive
evidence for endothelial gates and key questions remain unanswered;
however, it certainly provides an interesting alternative view to
the popular notion that S1P1 agonists cause sequestration of lymphocytes
due to internalisation of the receptors. |
||||||||||||||||
|
|||||||||||||||||
Benjamin Cravatt Evaluated 10 Jan 2006 |
This
paper describes the application of innovative chemical and cell biology
tools to delineate the mechanism of action of sphingosine 1-phosphate
(S1P) receptors in lymphocyte transendothelial migration.
Previous genetic studies had suggested that agonists of S1P receptors
might inhibit lymophocyte egress by acting as 'functional antagonists'
(i.e. downregulating these receptors). However, here, the authors
show, through the use of two-photon imaging of lymphocyte movement
in explanted lymph nodes, that S1P agonists cause a rapid block of
T cell migration that can be reversed by agonist removal or the inclusion
of an S1P receptor antagonist. These data suggest that S1P agonism,
rather than functional antagonism, is the cause of blockade of lymphocyte
egress. The authors propose a novel and provocative model for S1P
agonist function whereby these reagents act on receptors expressed
in endothelial cells (rather than lymphocytes) to inhibit lymphocyte
egress. These studies also have important biomedical implications,
as S1P receptors agonists may serve as useful immunosuppressant drugs.
|
||||||||||||||||
|
|
|||||||||||||||||
 |
126. Zhang S.L. Y. Yu, J. Roos,
J.A. Kozak, T.J. Deerinck, M.H. Ellisman, K.A. Stauderman, and M.D.
Cahalan. 2005.
|
|
|||||||||||||||
Bernd Nilius Evaluated 2 Feb 2006 |
This
manuscript reports on the functional impact of the Ca2+ binding protein
STIM1 (stromal interaction molecule) on store-operated (or Ca2+ release-activated)
Ca2+ influx (SOC, CRAC). STIM1, when located in the membrane of the
endoplasmic reticulum (ER), is likely the protein sensing the store
Ca2+ content, and depletion of intracellular Ca2+ stores stimulates
trafficking of STIM1 from the ER to the plasma membrane where it induces
channel forming. Importantly, mutations in the EF-hand
Ca2+ binding motif (the Ca2+ sensor in the ER) of STM1 constitutively
activate SOC without changing the store Ca2+ content. SOC/CRAC is
important for the regulation of a plethora of cells functions, ranging
from gene expression to cell proliferation. STIM1 may now open a novel
approach to solving the SOC/CRAC puzzle. |
||||||||||||||||
|
|||||||||||||||||
Anjana Rao |
This paper and another by Liou et al. {1} both show that the EF-hand protein STIM1 is an ER-localised Ca2+ sensor that relocalises intracellularly after depletion of intracellular Ca2+ stores. However, there remains some uncertainty about whether STIM1 actually inserts into the plasma membrane following store depletion, or relocalises to sites near the plasma membrane to form part of plasma-membrane-associated protein complexes that do not dissociate after detergent lysis under non-denaturing conditions. {1} Liou et al. Curr Biol 2005 15:1235-41 Evaluated 10 Nov 2005 |
||||||||||||||||
|
|||||||||||||||||
Colin Taylor
University of Cambridge, United Kingdom CELL BIOLOGY |
STIM1
is shown to provide the Ca2+ sensor that allows the Ca2+
content of intracellular stores to regulate the widely expressed store-operated
Ca2+ (SOC) entry pathway. STIM1 is required
for activation of SOC and it translocates from the ER to the plasma
membrane when intracellular Ca2+ stores are emptied. Mutation of the
luminal EF-hand-like Ca2+ - binding site of STIM1 causes
constitutive activation of SOC.
Evaluated 14 Oct 2005 |
||||||||||||||||
|
|||||||||||||||||
Annette Dolphin Evaluated 11 Oct 2005 |
This
paper reports the fascinating result that an ER resident transmembrane
protein Stim1 moves to the plasma membrane when ER Ca2+ stores are
depleted, and may itself represent the elusive CRAC (Ca2+ release
activated calcium) channel. Stim1 contains a low affinity
EF hand normally facing the ER lumen, and when this is mutated so
that it no longer binds Ca2+ , ICRAC becomes constitutively activated,
even when the stores are full. Furthermore, this mutant Stim1 is found
in the plasma membrane. The authors present two main possibilities,
either Stim1 multimerizes to form the CRAC channel or it associates
with other proteins that form this channel. Either way the elusive
channel is now nearer to being pinned down. Similar conclusions were
also reached by Liou et al. (Curr Biol 2005, 15:1235-41 [PMID:16005298]),
although the present paper goes a little further in showing convincingly
that Stim1 becomes inserted into the plasma membrane. |
||||||||||||||||
|
|||||||||||||||||
 |
124. Roos, J. DiGregorio, P.J.,
A.V. Yeromin, K. Ohlsen, M. Lioudyno, S. Zhang, O. Safrina, J.A. Kozak,
S. Wagner, M.D. Cahalan, G. Velicelebi, and K.A. Stauderman. 2005.
|
|
|||||||||||||||
| Mitsuhiko Ikura
University of Toronto, Canada STRUCTURAL BIOLOG |
A
mystery in regulatory mechanisms underlying store-operated Ca2+ (SOC)
influx has been solved! Through RNAi screens with 170 genes, the authors
identified a gene that gave a substantially reduced activity in thapsigargin-activated
Ca2+ entry. This gene encodes the already known membrane
protein called stromal interaction molecule-1 (STIM1), which probably
exists on the ER-membrane (some on the plasma membrane as well). STIM1
is now shown to play an essential role in SOC influx and may be a
common component of SOC and Ca2+ release-activated Ca2+ (CRAC) channels.
Evaluated 23 May 2005 |
||||||||||||||||
|
|||||||||||||||||
| Roger Hardie
University of Cambridge, United Kingdom NEUROSCIENCE |
Using
an RNAi screen to search for genes required for store-operated Ca2+
(SOC) entry, just one gene (out of 170 tested), STIM1 was found to
reduce Ca2+ entry in a Drosophila cell line. STIM1 is an
ubiquitously expressed novel protein associated with both plasma and
ER membranes; with just one transmembrane domain, it is unlikely to
represent the elusive SOC channel, but the authors suggest that it
may represent a Ca2+ sensor, coupling the ER and plasma membrane with
its N-terminal EF hand in the ER lumen. Intriguingly, despite including
all the known Drosophila TRP channels in the screen, none of these
was able to reduce Ca entry. Evaluated 9 May 2005 |
||||||||||||||||
|
|||||||||||||||||
| Colin Taylor
University of Cambridge, United Kingdom CELL BIOLOGY |
This
paper reports that STIM1, an integral membrane protein expressed in
ER and the plasma membrane, is required for store-operated Ca2+ entry
in diverse cell types. An RNAi-based screen of Drosophila
S2 cells established that from many candidate proteins, only STIM1
was essential for thapsigargin-activated Ca2+ entry. STIM1 may be
a ubiquitous component of store-regulated Ca2+ entry, with its EF-hand
perhaps sensing the Ca2+ content of the ER. Evaluated 4 May 2005 |
||||||||||||||||
|
|||||||||||||||||
 |
123. Okada, T., M.J. Miller, I.
Parker, M.F. Krummel, M. Neighbors, S.B. Hartley, A. O’Garra,
M.D. Cahalan, and J.G. Cyster.
|
|
|||||||||||||||
| James Crowe
Vanderbilt University School of Medicine, United States MICROBIOLOGY |
This paper uses of two-photon microscopy of intact lymph nodes to define the kinetics and anatomy of antigen-specific B-T cell interactions. The work demonstrates that B cells migrate in lymph nodes in a CCR7 gradient-determined fashion. The ability to define the number and duration of cell-cell interactions and the kinetics of chemotaxis leads to some fascinating images and a better understanding of the complexity of in vivo immune responses. Evaluated 20 Jun 2005 |
||||||||||||||||
|
|||||||||||||||||
| Peter Openshaw
Imperial College London, United Kingdom MICROBIOLOGY |
B
cells and T cells need to engage to make a good immune response, but
the way they do so has not been visualised before. Using two-photon
microscopy, B cells are now seen to move towards the T cell zone of
intact lymph nodes after exposure to antigen. Here, they
rest for a day before starting to dance through the T cells at a speedy
9 um/min, touching many but lingering over the few that are antigen-specific.
The T cells are then 'monogamous and clingy', hanging on to the B
cells that continue to move, searching for yet more partners. Evaluated 20 May 2005 |
||||||||||||||||
 |
|
||||||||||||||||
| 118. Yeromin A.V.,
J. Roos, K.A. Stauderman, and M.D. Cahalan. 2004.
|
|
||||||||||||||||
| Roger Hardie
University of Cambridge, United Kingdom NEUROSCIENCE |
A
detailed electrophysiological characterization of the store-operated
Ca (SOC) current in Drosophila S2 cells reveals that its properties
are extrmely close to those of mammalian ICRAC. Drosophila
S2 cells are ideally suited for high throughput, full genome screening
using RNAi gene silencing. This system thus has great potential for
the final molecular identification of the elusive SOC channels.  Evaluated 3 Feb 2004 |
||||||||||||||||
|
|||||||||||||||||
 |
117. Miller, M.J.,
A.S. Hejazi, S.H. Wei, I. Parker, and M.D. Cahalan. 2004.
|
|
|||||||||||||||
| Andrea Sant University of Rochester Medical Center, United States IMMUNOLOGY |
This
paper deals with the important issue of the mechanisms through which
rare naive T cells encounter low numbers of recently emigrated antigen-bearing
dendritic cells in peripheral lymph nodes. The authors employ a novel
approach to activate and label peripheral dendritic cells and to follow
their migration and encounter with T cells in the draining lymph nodes
using two photon microscopy. Their results show that extended
and rapidly moving dendrites from the dendritic cell body allow a
typical dendritic cell to collectively scan up to 5000 T cells per
hour. This sweeping scanning pattern of dendritic cells, coupled with
rapid and random motility of T cells accounts for the ultimate contact
between antigen bearing dendritic cells with rare antigen specific
T cells and thus the initiation of an antigen specific T cell response.
Evaluated 10 Aug 2004 |
||||||||||||||||
|
|||||||||||||||||
| Rick Tarleton
University of Georgia, United States IMMUNOLOGY |
Using
two-photon microscopy and injection of CFSE (carboxyfluorescein succinimidyl
ester) in alum, this study shows that in vivo labelled dendritic cells
(DCs) traffic from the skin to the draining lymph node where the sweeping
action of their dendrites and the random movement of T cells allow
each DC to make an estimated 5000 T cell contacts per hour.
At this rate, as few as 100 antigen-bearing DC were determined to
be able to efficiently screen for low frequency antigen-specific T
cells (1 in 10e6) in as little as 6 hours. Evaluated 24 Feb 2004 |
||||||||||||||||
|
|||||||||||||||||
| Michael Dustin
New York University School of Medicine, United States IMMUNOLOGY |
This
paper develops a new and highly effective method for labeling dendritic
cells in tissues for later visualization in explanted lymph nodes
or detection by flow cytometry. They find that the T cell
scanning rate of dendritic cells is 10-fold higher than earlier estimates,
probably due to better resolution of fine, dendritic processes which
make up much of dendritic cell surface area available for T cell contact.
The method consists of mixing microgram amounts of carboxyfluorescein
succinimidyl ester (CFSE) with alum and injecting it subcutaneously.
The CFSE appears to be trapped in the alum depot such that it does
not directly drain to the lymph node, but does label dermal dendritic
cells that migrate and reach the lymph node after several hours. Fluorescent
protein antigens could also be included in the alum suspension and
could be detected associated with the CFSE labeled dendritic cells.
This method is analogous to the FITC painting method for labeling
Langerhan's cells. An advantage of this approach is that it allows
visualization of cell populations that are directly relevant to vaccination
strategies. The authors provide additional support for their earlier
proposal that T cell repertoire scanning is primarily accomplished
by rapid, autonomous migration of T cells through a field of slower
migrating dendritic cells elaborating a high surface area to form
~300 contacts at any time and 5000 contacts per hour per dendritic
cell. Evaluated 3 Feb 2004 |
||||||||||||||||
|
|||||||||||||||||
 |
110. Miller, M.M.,
S.H. Wei, I. Parker, and M.D. Cahalan. 2003.
|
|
|||||||||||||||
Evaluated 12 Aug 2003 |
This
paper reports that T lymphocytes in lymph nodes in vivo display a
spectacular motility that can be described as a random walk within
the T cell zones. This behavior suggests that lymphocytes encounter
antigen-presenting cells through autonomous motility without a need
for specific chemoattraction. This study and previous organ culture
studies from the same lab have provoked a paradigm shift in thinking
about the early moments of the T cell-dendritic cell interaction.
T lymphocytes from DO.11 T cell receptor transgenic mice were labeled
with carboxyfluorescein succinimidylester (CFSE) and were transferred
into 4 week old MHC identical normal recipient mice. The mice were
anesthetized and the inguinal lymph node was surgically exposed and
mounted in a temperature controlled stage and the interior of the
lymph node was imaged with a two-photon laser scanning microscope
through natural windows in the adipose tissue surrounding the lymph
node in mice of this age. Blood flow was maintained as demonstrated
by the visualization of labeled T cells flowing in the microcirculation
of the node. Lymph flow was not verified, but the avoidance of surgery
near the node to remove adipose tissue means that afferent and efferent
lymphatic were likely intact. Z-stacks were obtained of lymph nodes
with sufficient time resolution to track the migration of T cells
within the T cell zones. The average velocity was 10.2-11.5 micrometers/min
with a peak velocity of up to 25 micrometers/min. While cells sometimes
briefly paused, there appeared to be no population of immobile cells.
The direction of motion appeared to be random in both parallel to
the capsule and axially. While the T cell frequently moved in a straight
line for ~30 micrometers before changing direction, the movement at
longer time scales was well modeled by a random walk where the slot
of displacement vs the square root of time was linear. The animals
were maintained during anesthesia with 95% oxygen and 5% carbon dioxide,
a gas mix that is used to elevate tissue oxygen levels. Therefore
the relationship of tissue O2 levels in this system to those in a
normal awake mouse is not known. The high rate of T cell autonomous
motility described here also provides a clear model for immune surveillance
in lymph nodes in which T cells may encounter many potential antigen
presenting cells in search of the "antigenic needle in a haystack"
to quote the authors. |
||||||||||||||||
|
|||||||||||||||||
| Ulrich Von Andrian
Harvard Medical School, United States IMMUNOLOGY |
This
in vivo analysis of the migratory dynamics of T cells in inguinal
lymph nodes validates earlier in vitro observations by this group
in excised lymph nodes, which have shown that naive T cells migrate
very rapidly and with apparently random directionality.
The finding that T cells act as autonomous agents challenges the concept
that interstitial chemokine gradients channel streams of migrating
T cells within lymph nodes. Evaluated 26 Mar 2003 |
||||||||||||||||
|
|||||||||||||||||
 |
104. Miller, M.M.,
S.H. Wei, I. Parker, and M.D. Cahalan. 2002.
|
|
|||||||||||||||
| Casey Weaver
University of Alabama at Birmingham, United States IMMUNOLOGY |
This study
introduces two photon-videomicroscopy to the study of T cell and B
cell motility, and T cell responses to specific antigen, in explanted
lymph nodes. Striking differences in the motilities of
T and B cells within the lymph node architecture are directly observed.
The kinetics and character of the response of T cells to specific
antigen are defined. Evaluated 1 Jul 2002 |
||||||||||||||||
|
|||||||||||||||||
| Jonathan Howard
Institut fur Genetik, Germany IMMUNOLOGY |
Modern microscopic methods, especially
two-photon laser scanning photography, allow direct visualisation
of live fluorochrome-labelled lymphocytes trafficking in lymphoid
tissues. Differentially labelled T and B cells move about
in complex trajectories after entering their characteristic regions
of a lymph node. The presence of an antigen specific for labelled
T lymphocytes induces perturbations in their movement. In particular,
stationary clusters and dynamic swarms form. Subsequently, the cells
enlarge and divide. Without breaking radical new ground conceptually,
these results demonstrate the validity of concepts of lymphocyte behaviour
obtained with disaggregated cell mixtures. They further demonstrate
the extraordinary power of the new microscopy. Evaluated 26 Jun 2002 |
||||||||||||||||
|
|||||||||||||||||
| Matthias von Herrath
La Jolla Institute for Allergy and Immunology, United States IMMUNOLOGY |
This is a very impressive advance
for the live tracking of ongoing antigen-specific immune responses,
and could be a first step in revolutionizing non-invasive imaging
techniques for understanding immunity. Direct visualization
of antigen-specific T cells and antigen-presenting cells in lymph
nodes and possibly other organs in the future will improve our comprehension
of the immune system. Evaluated 14 Jun 2002 |
||||||||||||||||
|
|
|
||||||||||||||||
|
|
|
|||||||||||||||
Maintained by Jeff Ingeman |
|
|
Physiology
and Biophysics, University of California,Irvine, CA, USA, 92697-4561 Phone: (949) 824-6754 • Fax: (949) 824-3143 • Email:mcahalan@uci.edu |
|
|
Modified: 04/17/2006 |
|||||||||||
