Signalling Mechanisms: Part 2 - Secondary Messengers and Signalling Networks

These flashcards cover key vocabulary from the lecture on signaling mechanisms, focusing on secondary messengers and signaling networks.

Secondary Messenger

A molecule that transmits a signal within a cell after the receptor has been activated.

G Protein

A guanine nucleotide-binding protein that transmits signals from receptors to effector proteins.

cAMP

Cyclic adenosine monophosphate, a common secondary messenger involved in signal transduction.

Receptor Tyrosine Kinases

A class of membrane receptors that have intrinsic enzyme activity for phosphorylating tyrosine residues.

Phospholipase-C

An enzyme that hydrolyzes phosphatidyl inositol, generating diacylglycerol and IP3.

Adenylyl Cyclase

An enzyme that converts ATP to cAMP in response to an activated G protein.

Calcium Ions (Ca2+)

An important secondary messenger that is released from internal reserves to trigger various cellular responses.

Insulin

A hormone that stimulates glucose uptake and regulates metabolism through signaling pathways.

Akt

A protein kinase that is activated by PI 3-kinase and plays a key role in cell survival signaling.

Transcription Factor

A protein that regulates the transcription of specific genes by binding to nearby DNA.

Endocytosis

A process by which cells internalize substances from their outer environment, potentially affecting signaling.

Ras Protein

A GTPase that acts as a molecular switch in signaling pathways, particularly those related to growth.

Gene Expression

The process by which information from a gene is used to synthesize functional gene products.

Phosphorylation

The addition of a phosphate group to a molecule, often regulating enzyme activity and signaling pathways.

Signal Transduction

The mechanism through which a signal is converted into a functional response within a cell.

GPCR (G Protein-Coupled Receptors)

A large family of receptors that detect various stimuli and activate G proteins.

FOXO Transcription Factor

A transcription factor that regulates genes involved in apoptosis and metabolism in response to signaling.

cAMP Phosphodiesterase

An enzyme that hydrolyzes cAMP to AMP, thereby terminating its signaling effects.

IP3 (Inositol Triphosphate)

A secondary messenger that promotes the release of calcium ions from the endoplasmic reticulum.

Gene Transcription

The process by which a segment of DNA is copied into RNA by the enzyme RNA polymerase.

MEK (MAPK/ERK Kinase)

A dual-specificity protein kinase that activates ERK, a key component of many signaling pathways.

Protein Kinase

An enzyme that catalyzes the transfer of a phosphate group from ATP to a protein, often altering its function.

Protein Phosphatase

An enzyme that removes phosphate groups from proteins, typically reversing the effects of protein kinases.

MAPK Pathway

The Mitogen-Activated Protein Kinase pathway, a central signaling cascade involved in cell growth, proliferation, and differentiation.

PI3-Kinase (Phosphoinositide 3-Kinase)

An enzyme that phosphorylates phosphatidylinositol, producing second messengers involved in cell growth, survival, and metabolism.

Diacylglycerol (DAG)

A secondary messenger produced by phospholipase C that remains embedded in the membrane and activates Protein Kinase C.

Scaffolding Protein

A protein that physically brings together multiple components of a signaling pathway, enhancing efficiency and specificity.

Receptor

A cellular protein that binds a specific ligand, initiating a cellular response.

Effector Protein

A protein that carries out the final cellular response after being activated by upstream signaling components.

Protein Kinase C (PKC)

A family of protein kinases that are activated by diacylglycerol (DAG) and calcium ions, playing roles in various cellular processes.

Desensitization

A mechanism by which a cell's response to a prolonged stimulus is attenuated over time.

Autophosphorylation

The phosphorylation of a protein kinase by itself, often occurring in receptor tyrosine kinases upon ligand binding.

Signal Amplification

A process in cellular signaling where a small number of extracellular signals can lead to a large cascade of intracellular events and a robust response.

Protein Kinase A (PKA)

A protein kinase that is activated by cAMP and phosphorylates target proteins, mediating various cellular responses.

Calmodulin

A calcium-binding protein that acts as a calcium sensor and mediates many calcium-dependent cellular processes.

Ligand-gated Ion Channel

A transmembrane protein that opens to allow ions to pass through the membrane in response to the binding of a specific ligand.

Intracellular Receptor

A receptor located inside the cell that binds to hydrophobic signaling molecules (e.g., steroid hormones) which can cross the plasma membrane.

Conformational Change

A change in the three-dimensional shape of a protein, often induced by ligand binding or phosphorylation, that can alter its activity or interactions.

GTPase-Activating Protein (GAP)

A regulatory protein that promotes the hydrolysis of GTP to GDP by a G protein, thereby inactivating the G protein.

Guanine Nucleotide Exchange Factor (GEF)

A regulatory protein that facilitates the exchange of GDP for GTP on a G protein, thereby activating the G protein.

Nuclear Receptor

A class of intracellular receptors that, upon ligand binding, translocate to the nucleus to directly regulate gene transcription.

Receptor Downregulation

A decrease in the number of receptors on the cell surface, often in response to chronic exposure to a ligand, leading to reduced cellular sensitivity.