Cell Signaling 1 Flashcards
What is Direct cell-to-cell signaling?
A signaling molecule expressed on the surface of one cell interacts with a receptor localized on the surface of an adjacent cell
What is endocrine signaling?
the signaling molecules (hormones) are released from secretory cells into the blood and carried to distant target tissues
What is paracrine signaling?
signaling cells exert their effects locally on neighboring cells; they reach the target cells via the interstitial fluid
E.g. neurotransmitters via the synaptic junction
What is autocrine signaling?
signaling molecules bind to receptors in or on the cells that release them
What is the function of gap junctions?
Connect the cytoplasm of adjacent cells, allows signaling via small intracellular chemical mediators
What are the functions of receptors?
To recognize and bind specific ligands
To elicit a response by the target cell when the receptor is occupied by activating one or more intracellular signal transduction pathways
What are four properties of receptors?
High specificity - able to distinguish between closely related molecules
High Affinity - bind at low conc.
Reversible reaction
Saturable
What determines a receptor’s affinity for a particular ligand?
The number and strength of the non-covalent interactions that are formed
What is Kd?
The dissociation constant, an important quantitative measure of the affinity of a receptor for a specific ligand
Kd is the concentration of ligand at which 1/2 of the receptors are occupied.
What can binding studies be used to determine?
The total number of receptor binding sites (Bmax)
The affinity of the receptor (Kd)
What cannot be measured directly using binding studies?
The concentration of unoccupied receptor binding sites [R]
What three things can modulate the response of a target cell to a specific signaling molecule?
Changes in ligand concentration - can be too high or too low
Changes in Bmax - receptor up- and down-regulation
Changes in Kd - covalent modification of receptor, mutation
How can a given signaling molecule activate more than one response?
Ligands can bind different receptor types that have different tissue distributions and work through different signaling pathways
What is vasopressin binding to V1 and V2 receptors and example of?
A signaling molecule inducing different signaling pathways for different receptor types.
Vasopressin
V1 - intracellular Ca+
V2 - cAMP second messenger pathway
What are catecholamines and example of?
A signaling molecule eliciting diverse and often antagonistic effects in different tissues
Epinephrine and norepinephrine
contraction of smooth muscle in arterioles
relaxation of smooth muscle in airways
