Unit 3 Vocabulary - Intracellular Signaling

Ligand

Molecule that binds to the receptor

Autocrine

The cell has receptors on its surface that respond to released messengers produced from itself (e.g. growth of cells in tumor)

Endocrine

Messenger molecules reach their target cell through the bloodstream (e.g. hormones)

Paracrine

The cell has receptors on its surface that respond to released messengers produced by other cells nearby (e.g. neuron-neuron signaling)

Juxtacrine

Requires that cells come into contact with each other through a membrane-bound signal molecule

Receptor Tyrosine Kinases

Activate the GTPase Ras and assemble signaling complexes

G protein Coupled Receptors (GPCRs)

A family of proteins that perceive many extracellular signals and transduce them to heterotrimeric G proteins

Effectors

Proteins altered in response to a ligand

Second messenger

molecule produced by activated receptor and effector as a cellular response to signaling (e.g. calcium activates the protein kinase calcineurin)

Protein kinases

Covalently add one or more phosphate groups to specific amino acids at hydroxyl groups

Protein phosphatases

Removes phosphate groups from amino acids

GTP-binding proteins

Switch between two conformational states: GTP-bound is active and GDP-bound is off

GTPase-activating Proteins (GAPs)

Activate GTPase to increase the rate of hydrolysis of bound GTP, turning the GTP-binding protein off

Guanine nucleotide exchange factors (GEFs)

Promotes release of bound GDP in exchange for GTP, turning the GTP-binding protein on

Signal transduction

Extracellular messenger molecules can elicit intracellular responses