Lecture 3-12: General Principles of Cell Signaling

Signal Transduction

The process by which one form of a message is transformed into another form, typically involving the conversion of an extracellular stimulus into a cellular response.

Paracrine Signaling

A type of cell communication where a soluble signal is released into the local environment and affects any cell with a receptor that recognizes the signal.

Autocrine Signaling

A type of signaling where the cell that releases the signal also has receptors for it, allowing it to respond to its own signal.

Neuronal (Synaptic) Signaling

Cell communication that involves the release of a soluble signal molecule into the narrow space between cells, known as the synapse.

Contact-Dependent Signaling

Cell communication that requires physical contact between signaling and target cells through membrane-bound receptors.

Endocrine Signaling

A signaling pathway where soluble signaling molecules are released into the bloodstream to reach distant target cells.

Ion-Channel-Coupled Receptors

Receptors that open or close in response to binding of a ligand, altering membrane potential and facilitating signaling.

G Protein-Coupled Receptors (GPCRs)

Receptors that are associated with an inactive trimeric G protein complex, involved in various signaling pathways upon ligand binding.

Enzyme-Coupled Receptors

Receptors that have intrinsic catalytic activity or recruit enzymes upon ligand binding, often involved in signaling through phosphorylation.

Phosphorylation

A common molecular switch in signaling pathways where the addition of a phosphate group alters protein function.

GTP Binding

A molecular mechanism whereby G proteins are activated by binding to GTP, functioning as signaling mediators.

Epinephrine

A polar hormone produced in the adrenal gland that increases heart rate, blood pressure, and metabolism; acts via surface receptors.

Intracellular Receptors

Receptors located within the cell that typically bind hydrophobic ligands and act primarily as transcription factors.

Apoptosis

Programmed cell death that can be triggered by the absence of survival signals or inappropriate signaling.

Integration of Signals

The process in which different signals converge to produce varied cellular responses depending on the combination of signals received.

Negative Feedback

A regulatory mechanism where a downstream factor inhibits an upstream factor, often leading to stable or oscillatory signaling responses.