Signalling Mechanisms: Part 1

These flashcards cover key vocabulary related to cell signaling mechanisms, including definitions of various types of signaling, receptor functions, and processes involved in signal transduction.

GAP-junctions

Intercellular channels that permit direct cell-cell transfer of ions and small molecules.

Endocrine Signaling

A type of long-range signaling where hormones are carried through the circulatory system to act on distant target cells.

Paracrine signaling

Local signaling in which a molecule released from one cell affects nearby target cells through diffusion.

Autocrine signaling

When a cell generates a signaling molecule that it reacts to itself, reinforcing its own identity.

Phosphorylation

A common posttranslational modification that regulates protein activity and is involved in most signaling pathways.

7TM receptors

Transmembrane receptors with seven regions that typically interact with G proteins, also known as G protein-coupled receptors (GPCRs).

Receptor Tyrosine Kinases

A category of receptors that have intrinsic enzymatic activity and play a significant role in responding to growth factors.

Dimerization

A mechanism for activating receptor tyrosine kinases where receptor monomers bind together, facilitating transphosphorylation.

Glucocorticoid receptor

A receptor that, when bound by glucocorticoids, translocates to the nucleus and stimulates transcription of target genes.

Second messenger

Small molecules that help relay signals within a cell after the initial signal is detected by a receptor.

Signal Transduction

The process by which a cell converts an extracellular signal into an intracellular response, often involving a series of molecular events.

Ligand

A molecule that binds specifically to another molecule, usually a larger one, such as a receptor protein.

G Proteins

Heterotrimeric proteins (composed of \alpha, \beta, and \gamma subunits) that are activated by GPCRs and regulate the activity of various effector proteins.

Cyclic AMP (cAMP)

A common second messenger derived from ATP, involved in many signaling pathways, particularly those mediated by G protein-coupled receptors.

Ion Channel-Linked Receptors

Cell-surface receptors that open or close an ion channel in response to ligand binding, thereby altering the ion permeability of the plasma membrane.

Adenylyl Cyclase

An enzyme that is often activated by G proteins and converts ATP into cyclic AMP (cAMP), a key second messenger.

Diacylglycerol (DAG) and Inositol Trisphosphate (IP3)

Two important second messengers produced from the cleavage of a membrane phospholipid by phospholipase C, involved in activating protein kinase C and releasing intracellular calcium, respectively.

Protein Kinase A (PKA)

A serine/threonine kinase that is activated by cyclic AMP (cAMP) and phosphorylates various target proteins, mediating many cellular responses to hormones and neurotransmitters.

Calcium (Ca2+)

A crucial second messenger that regulates many cellular processes, often released from intracellular stores in response to IP3, or entering the cell via ion channels.

Phospholipase C (PLC)

An enzyme activated by various receptors (e.g., GPCRs, RTKs) that cleaves PIP2PIP2​ into inositol trisphosphate (IP3) and diacylglycerol (DAG), both acting as second messengers.

Protein Kinase C (PKC)

A family of serine/threonine kinases that are activated by diacylglycerol (DAG) and calcium (Ca2+Ca2+) and phosphorylate target proteins to mediate various cellular responses.

MAP Kinase Pathway

A key signaling cascade (e.g., Ras-Raf-MEK-ERK) involved in cell growth, proliferation, differentiation, and survival, often activated downstream of Receptor Tyrosine Kinases.

Guanine Nucleotide Exchange Factors (GEFs)

Proteins that activate monomeric GTPases (like Ras) by promoting the release of GDP and the binding of GTP.

GTPase-Activating Proteins (GAPs)

Proteins that inactivate monomeric GTPases by stimulating their intrinsic GTP hydrolysis activity, converting GTP to GDP.

Scaffold proteins

Proteins that bind multiple signaling components in a pathway, localizing them to specific regions of the cell and promoting efficient signal relay.

Signal amplification

A process in cell signaling where a small number of extracellular signal molecules can produce a large intracellular response, often through enzymatic cascades.

cAMP Phosphodiesterase

An enzyme that breaks down cyclic AMP (cAMP) into 5'-AMP, thereby terminating cAMP-mediated signaling.

Calmodulin

A ubiquitous calcium-binding protein that acts as a second messenger receptor, mediating many of the intracellular effects of Ca^{2+} by binding to and regulating various target proteins.

Receptor Desensitization

A process where a cell becomes less responsive to a prolonged stimulation by a ligand, often involving receptor phosphorylation, internalization, or degradation, preventing overstimulation.

Signal Integration

The process by which cells receive multiple signals and combine them to produce a unified response, allowing for complex and finely tuned cellular behaviors.