Single-Molecule Analysis of Chemotactic Signaling in Dictyostelium Cells
Masahiro Ueda,16*
Yasushi Sako,26
Toshiki Tanaka,4
Peter Devreotes,5
Toshio Yanagida36
Single-molecule imaging techniques were used to reveal
the binding of individual cyclic adenosine 3',5'-monophosphate
molecules to heterotrimeric guanine nucleotide-binding protein coupled
receptors on the surface of living Dictyostelium discoideum
cells. The binding sites were uniformly distributed and diffused
rapidly in the plane of the membrane. The probabilities of individual
association and dissociation events were greater for receptors at the
anterior end of the cell. Agonist-induced receptor
phosphorylation had little effect on any of the monitored
properties, whereas G protein coupling influenced the binding kinetics.
These observations illustrate the dynamic properties of receptors
involved in gradient sensing and suggest that these may be polarized in
chemotactic cells.
1 Recognition and Formation,
2 Time's Arrow and Biosignaling, Precursory
Research for Embryonic Science and Technology (PRESTO), Japan Science
and Technology Corporation (JST).
3 Single
Molecule Processes Project, International Cooperative Research Project
(ICORP), JST, Mino, Osaka 562-0035, Japan.
4 Biomolecular Engineering Research Institute,
Suita, Osaka 565-0874, Japan.
5 Department of Cell
Biology, Johns Hopkins Medical Institutions, Baltimore, MD 21205, USA.
6 Department of Physiology and Biosignaling,
Graduate School of Medicine, Osaka University, Suita, Osaka 565-0871, Japan.
*
To whom correspondence should be addressed. E-mail:
ueda{at}phys1.med.osaka-u.ac.jp
Present address: Department of Applied Chemistry,
Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan.
