BIOL 4610: Cell Signaling

Cell signaling

Allows cells to communicate with one another about growth, differentiation, metabolism

Endocrine signaling

• Long range signaling

• Release of a hormone into bloodstream and influences target cells

Paracrine signaling

• Short range signaling

• Signaling molecule acts as a local mediator and influences target cells in the vicinity

Synaptic signaling

• Long range signaling

• Neurotransmitter is released from the axon of the nerve cell and is received by a target cell

Hydrophilic signaling molecules often interact with the target membrane through __

Cell-surface receptors

Hydrophobic signaling molecules often interact with __

Intracellular receptors

Hydrophobic signaling molecules delivered to a target cell through a __

Carrier protein

Alpha subunit

• Part of the G protein

• Once activated it separates from the other subunits and binds GTP

Stimulatory G protein (Gs)

When activated, the activity of adenyl cyclase increases, leading to an increase in cAMP levels. This activate PKA which further enhances adenyl cyclase activity

Inhibitory G proteins (Gi)

When activated, the activity of adenyl cyclase decreases, leading to a decrease in cAMP levels. This lowers the activity of PKA which stops the amplification of the signal, reducing the overall cellular response

cAMP dependent pathway

Signal transduction mechanism in which the binding of a ligand to a G protein-coupled receptor activates adenylate cyclase, increasing cAMP levels and activating protein kinase to regulate cellular response

Effects of PKA activation:

• Glycogen breakdown in muscle and liver

• Changes in gene expression

• CFTR (ion channel) activation

Cholera toxin:

Modifies a subunit and “locks” Gs in the GTP-bound state ON

Pertussis toxin:

Modifies a subunit and locks Gi in the GDP-bound state OFF