Signal Transduction Flashcards
Drug-Receptor Complex
The magnitude of the response is proportional to the number of drug-receptor complexes. Drug + Receptor = Drug-receptor complex= biologic effect.
What are the major receptor families?
Transmembrane ligand-gated ion channels, transmembrane G protein coupled receptors, enzyme linked receptors, intracellular receptors
Transmembrane ligand-gated ion channels
Ligand-gated ion channels that are responsible for the regulation of the flow of ions across cell membranes. Regulated by the binding of a ligand to the channel. Example: cholinergic nicotinic receptors
Transmembrane G protein coupled receptors
G protein coupled receptors. Comprise a single alpha helical peptide that has 7 membrane spanning regions. The extracellular domain contains the ligand binding area. Most abundant type of receptors. 2nd messengers are used to amplify signals coming from G protein coupled receptors. Example: alpha and beta adrenoreceptors
Enzyme linked receptors
Consists of a protein that spans the membrane once and may form dimers or multi-subunit complexes. Have systolic enzyme activity as an integral component of their structure and function. Example: insulin receptors
Intracellular receptors
The receptor is entirely intracellular, therefore the ligand must diffuse into the cell to interact with the receptor. Example: steroid receptors
What is signal amplification?
It is the ability to amplify the signal duration and intensity. A single ligand receptor complex can interact with many G proteins, multiplying the original signal manyfold. The activated G protein persists for a longer duration than the original ligand receptor complex. Because of this amplification, only a fraction of the total receptors for a specific ligand may need to be occupied to elicit a maximal response.
What is desensitization?
The receptors are still present on the cell surface but are unresponsive to the ligand due to repeated or continuous administration of a med.
What is tachyphylaxis?
When repeated administration of a drug results in a diminished effect. Acute desensitization.
What is down-regulation?
Receptors can be down regulated in the presence of continuous stimulation. Binding of the agonist results in molecular changes in the membrane bound receptors, such that the receptor undergoes endocytosis and is sequestered within the cell, unavailable for further agonist interaction.
What is potency?
A measure of the amount of drug necessary to produce an effect of a given magnitude. The concentration of drug producing an effect that is 50% of the max is used to determine potency.
What is efficacy?
The ability of the drug to elicit a response when it interacts with a receptor. It is dependent on the number of drug-receptor complexes formed and the efficiency of the coupling of receptor activation to cellular responses. It is more important than potency.
