Related Experiment Videos
A radioactive binding assay for inhibitors of trkA kinase
E Knight1, T J Connors, A C Maroney
1Cephalon, Inc., West Chester, Pennsylvania 19380, USA.
Abstract:
The high-affinity receptor for nerve growth factor (NGF), trkA, is a receptor-linked tyrosine kinase. The binding of NGF to trkA, depending on the context of its environment, can cause beneficial or deleterious responses in the target cells. For example, the activation of trkA in sympathetic and sensory neurons causes the subsequent survival and differentiation of these cells. On the other hand, the activation of trkA by NGF in other cells has been implicated in several pathologies including inflammation-induced hyperalgesia and several cancers. A radioactive binding assay to evaluate inhibitors of the kinase domain of trkA has been developed and validated. The assay monitors the specific binding of an inhibitor of trkA kinase activity, the indolocarbazole K-252a, to the trkA receptor. [3H]K-252a binds with high affinity to one site on the cytoplasmic kinase domain of the trkA receptor. Binding is saturable and reversible with a dissociation constant (Kd) of 1.5 nM. The binding assay has been used in competition binding experiments to determine the inhibition constants for other indolocarbazole compounds. The IC50 values for compounds obtained in the binding assay correlate very well with the IC50 values obtained in an enzyme-linked immunosorbent assay for trkA tyrosine kinase activity.
Insights
A new radioactive binding assay was developed to test inhibitors of the trkA receptor tyrosine kinase. This assay accurately measures the binding affinity of compounds like K-252a, crucial for understanding trkA
Area of Science:
- Neuroscience
- Molecular Biology
- Biochemistry
Background:
- The high-affinity nerve growth factor (NGF) receptor, trkA, is a receptor-linked tyrosine kinase.
- NGF binding to trkA can promote neuronal survival or contribute to pathologies like cancer and hyperalgesia.
- Targeting trkA kinase activity is a potential therapeutic strategy.
Purpose of the Study:
- To develop and validate a radioactive binding assay for evaluating inhibitors of the trkA kinase domain.
- To characterize the binding kinetics of a known trkA inhibitor, K-252a.
Main Methods:
- Development and validation of a radioactive binding assay using [3H]K-252a.
- Measurement of specific binding of [3H]K-252a to the cytoplasmic kinase domain of the trkA receptor.
- Competition binding experiments to determine inhibition constants (IC50) for other indolocarbazole compounds.
Main Results:
- [3H]K-252a binds to a single site on the trkA kinase domain with high affinity (Kd = 1.5 nM).
- Binding is saturable and reversible.
- Assay IC50 values for indolocarbazole compounds strongly correlate with those from an enzyme-linked immunosorbent assay for trkA tyrosine kinase activity.
Conclusions:
- The developed radioactive binding assay is a validated method for assessing trkA kinase inhibitors.
- The assay provides reliable IC50 values that correlate well with functional enzyme activity assays.
- This assay facilitates the discovery and characterization of novel trkA-targeting compounds.