of cats (41) and in the amygdaloid complex of rats,
which expresses both slow and fast rhythms (but
no ripple-like events during SWS) (42). Conversely, rat hippocampal firing patterns during cortical slow waves (43) resemble the cortical firing
in Pogona around DVR sharp waves. Further
work is thus needed to clarify the relationship
between DVR, a dominant part of the reptilian
forebrain, and its potential mammalian equivalent (44).
Recent work on mammalian hippocampal
ripples focuses on their potential importance
for memory transfer and consolidation through
accelerated replay of awake-state activity and
activation of synaptic plasticity rules in cortical
targets (32, 33). In rats, correlations between
CA1 ripples and cortical spindles have been demonstrated (26). Our results in a reptile suggest
that there is also a functional relationship between the DVR and cortex. The projections between the DVR and cortex are extensive, direct,
and reciprocal. This offers an opportunity to test
the potential generality of the principle whereby
sleep ripples participate in memory transfer and
consolidation. More generally, the existence of
sleep-related dynamics in the brains of reptiles
may shed new light on general principles of information processing during sleep.
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This research was funded by the Max Planck Society and the
European Research Council (G.L.) and by fellowships from the
Minerva Foundation (M.S.-I.) and the Swiss National Science
Foundation (J.M.O.). The code for analysis and partial data are
available at www.brain.mpg.de/sheinidelsonetal2016, and the full
primary data are available from G.L. on request. The authors are
grateful to G. Wexel for help in surgery and postoperative care;
M. Klinkmann, A. Arends, Á. M. Pardo, T. Manthey, and C. Thum
for technical assistance; F. Baier, T. Maurer, G. Schmalbach, and
A. Umminger for help with mechanical design and fabrication;
N. Heller for help with electronics; K. Schröder and C. Schürmann
(Goethe University Medical School, Institute for Cardiovascular
Physiology) for help with m-CT scanning of lizards; the animal
caretaker crew for lizard care; and T. Tchumatchenko, H. Ito,
M. Kaschube, E. Schuman, A. Siapas, and the Laurent laboratory
for their suggestions during the course of this work or on
Materials and Methods
Figs. S1 to S10
29 January 2016; accepted 1 April 2016
Phase separation of signaling
molecules promotes T cell receptor
Xiaolei Su,1,2 Jonathon A. Ditlev,1,3 Enfu Hui,1,2 Wenmin Xing,1,3 Sudeep Banjade,1,3
Julia Okrut,1,2 David S. King,4 Jack Taunton,1,2 Michael K. Rosen,1,3† Ronald D. Vale1,2†
Activation of various cell surface receptors triggers the reorganization of downstream
signaling molecules into micrometer- or submicrometer-sized clusters. However, the
functional consequences of such clustering have been unclear. We biochemically
reconstituted a 12-component signaling pathway on model membranes, beginning with
T cell receptor (TCR) activation and ending with actin assembly. When TCR phosphorylation
was triggered, downstream signaling proteins spontaneously separated into liquid-like
clusters that promoted signaling outputs both in vitro and in human Jurkat T cells.
Reconstituted clusters were enriched in kinases but excluded phosphatases and enhanced
actin filament assembly by recruiting and organizing actin regulators. These results
demonstrate that protein phase separation can create a distinct physical and biochemical
compartment that facilitates signaling.
Many cell surface receptors and down- stream signaling molecules coalesce into micrometer- or submicrometer-sized clus- ters upon initiation of signaling(1, 2). How- ever, the effect of this clustering on signal
transduction is poorly understood. T cell recep-
tor (TCR) signaling is a well-studied example of
this general phenomenon (3). TCR signaling pro-
ceeds through a series of biochemical reactions
that can be viewed as connected modules. In the
upstream module, the TCR is phosphorylated by
Lck, a membrane-bound protein kinase of the
Src family. TCR phosphorylation is opposed by
a transmembrane phosphatase, CD45 (3). The
phosphorylated cytoplasmic domains of the TCR
complex recruit and activate the cytosolic tyrosine
kinase ZAP70 (4). In the intermediate module,
ZAP70 phosphorylates the transmembrane pro-
tein LAT (linker for activation of T cells) on mul-
tiple tyrosine residues. These phosphotyrosines