2010-ASCB-Press-Book - page 9

T h e A m e r i c a n s o c i e t y f o r C e l l B i o l o g y
News from
The American Society
for Cell Biology
50th Annual Meeting
Philadelphia, PA
December 11–15, 2010
Lonely parasite turns party animal
10:00 am, U.S. Eastern Time
Monday, December 13, 2010
Kent Hill
University of California, Los
609 Charles E. Young Dr.
Los Angeles, CA 90095
Author presents
Monday, December 13, 2010
8:35 am–8:55 am
Minisymposium: Host–Pathogen
Room 113
Program: 920
Signaling Pathways in the
Flagellum of Trypanosoma
brucei Are Required for
Responding to External Signals
Kent L. Hill
, Michael Ober-
, Miguel A. Lopez
Z. Pius Kabututu
, and James
1 Department of Microbiology,
Immunology, and Molecular
Genetics, UCLA, Los Angeles, CA
2 Molecular Biology Institute,
UCLA, Los Angeles, CA
3 Department of Biological
Chemistry, UCLA, Los Angeles, CA
The trypanosome behind African
sleeping sickness reveals an
unexpected talent for social
behavior and communication
arasites such as
are known for many things—
their diabolical two-host life cycle
and the mass human misery that they
inflict through diseases such as African
sleeping sickness—but until now, they
were not known for their social behavior.
T. brucei
was thought to be a freewheeling
loner, a protozoan that used its distinctive
flagellum as a propeller while it cycled
between its tsetse fly and human hosts.
Now researchers at the University of Cali-
fornia, Los Angeles (UCLA) report that at
the right time and on the right surface,
can be extremely social.
Seeded onto a semisolid surface,
T. brucei
in the tsetse fly stage of their
life cycle collect into large multicellular
communities whose members sense their
environment, exchange messages, and
coordinate their movements in response
to external signals. This unexpected dis-
covery reveals “a level of complexity and
cooperativity to trypanosome behavior
that was not previously recognized,” says
UCLA’s Kent Hill. The finding also sug-
gests a whole repertoire of behavior for
other “loner” parasites beyond
T. brucei,
with immense medical and economic
T. brucei’s
flagellum provided the
tip-off, says Hill. In many other parasites,
the long, whip-like flagellum also serves
as an antenna, picking up signals and
directing the parasite’s response. Hill
and colleagues took a closer look at the
proteins exposed on the outside of the
trypanosome flagellum, identifying a
family of surface-exposed receptors and
downstream signaling cascades involved
in cAMP signaling. Using genetics to block
gene expression and drugs to block pro-
tein activity, the researchers found that
these flagellar sensing and signaling sys-
tems equipped trypanosomes for normal
social behavior.
“The concept of bacteria acting as
groups of cells communicating and coop-
erating with one another has had a major
impact on our understanding of bacterial
physiology and pathogenesis, but this
paradigm has not been applied to para-
sitic protozoa,” says Hill. “Social motility
offers many potential advantages, such as
facilitating colonization and navigation
through host tissues.”
The identification of social behavior
T. brucei
throws the parasite into a new
and unexpected light, says Hill, forcing
researchers to rethink their traditional
concepts of host–parasite interactions.
This work was supported by the Burroughs
Wellcome Fund, the NIH National Institute
of Allergy and Infectious Diseases, and the
Swiss National Science Foundation.
African trypanosomes (left) engage in social behavior upon exposure to semisolid surfaces.
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