Neurexin/neuroligin interaction kinetics characterized by counting single cell-surface attached quantum dots.
Biophysical Journal. 2009-07-01; 97(2): 480-489
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1. Biophys J. 2009 Jul 22;97(2):480-9. doi: 10.1016/j.bpj.2009.04.044.
Neurexin/neuroligin interaction kinetics characterized by counting single
cell-surface attached quantum dots.
Saint-Michel E(1), Giannone G, Choquet D, Thoumine O.
(1)Physiologie Cellulaire de la synapse, Centre National de la Recherche
Scientifique and University of Bordeaux, Bordeaux, France.
We report what to our knowledge is a new method to characterize kinetic rates
between cell-surface-attached adhesion molecules. Cells expressing specific
membrane receptors are surface-labeled with quantum dots coated with their
respective ligands. The progressive diminution in the total number of
surface-diffusing quantum dots tracked over time collectively reflects intrinsic
ligand/receptor interaction kinetics. The probability of quantum dot detachment
is modeled using a stochastic analysis of bond formation and dissociation, with a
small number of ligand/receptor pairs, resulting in a set of coupled differential
equations that are solved numerically. Comparison with the experimental data
provides an estimation of the kinetic rates, together with the mean number of
ligands per quantum dot, as three adjustable parameters. We validate this
approach by studying the calcium-dependent neurexin/neuroligin interaction, which
plays an important role in synapse formation. Using primary neurons expressing
neuroligin-1 and quantum dots coated with purified neurexin-1beta, we determine
the kinetic rates between these two binding partners and compare them with data
obtained using other techniques. Using specific molecular constructs, we also
provide interesting information about the effects of neurexin and neuroligin
dimerization on the kinetic rates. As it stands, this simple technique should be
applicable to many types of biological ligand/receptor pairs.
PMID: 19619462 [Indexed for MEDLINE]