Signal Transduction Part I: Understanding Communication between Cells and Tissues

A set of vocabulary flashcards covering key terms and concepts from the lecture notes on intercellular and intracellular signaling.

Intercellular signaling

Communication between cells via signaling molecules to coordinate responses in target cells; influenced by distance, dilution, number of targets, and time/duration.

Endocrine signaling

Signaling molecules (hormones) released into the bloodstream to act on distant target cells.

Paracrine signaling

Signaling molecules affect nearby cells within the same tissue.

Autocrine signaling

Signaling molecules act on the secreting cell itself.

Juxtacrine signaling

Contact-dependent signaling requiring direct cell–cell contact.

Ion-Linked Receptor

Cell surface superfamily: targeted by most of the major neurotransmitter

Cytokine Receptors

Cell surface superfamily that recruit non-receptor tyrosine kinases (e.g., JAKs) to activate signaling pathways. play critical roles in immune and inflammatory responses

Enzyme-Linked Receptor

• Associated enzyme activity is usually a kinase

• Mutations in enzyme-linked receptors for certain growth factors, or their downstream signaling partners, underlie many cancers and developmental abnormalities

G Protein-Coupled Receptors (GPCRs)

cell surface superior family signaling through G proteins to regulate downstream effectors.

Receptor tyrosine kinase (RTK)

Receptor with intrinsic tyrosine kinase activity activated by ligand-induced dimerization and autophosphorylation.

Enzyme-linked (Catalytic) Receptors

Receptors with catalytic activity (e.g., kinases, guanylyl cyclases) that transduce signals upon ligand binding.

Intracellular/Nuclear receptors

Receptors located inside the cell that bind hydrophobic ligands and regulate gene expression by DNA binding.

Ligand

Molecule that binds to a receptor to modulate its activity.

Agonist

A ligand that activates receptor signaling.

Antagonist

A ligand that prevents receptor activation and signaling.

Kd (dissociation constant)

Affinity measure of the receptor–ligand binding; lower Kd means higher affinity.

EC50

Concentration of agonist that produces 50% of the maximal response; reflects potency.

Second messengers

Intracellular signaling molecules such as cAMP, cGMP, DAG, IP3, and Ca2+ that propagate signals inside the cell.

cAMP and cGMP

Cyclic nucleotides acting as second messengers to regulate kinases and ion channels.

DAG and IP3

Second messengers produced by phospholipase C; DAG activates PKC, IP3 releases Ca2+ from stores. Lipd derived products

Ca2+ as a second messenger

Ion that regulates numerous enzymes and processes when cytosolic levels rise.

MAP kinases

Mitogen-activated protein kinases that relay signals from RTKs to changes in gene expression and metabolism.

JAK/STAT pathway

Signaling cascade activated by cytokine receptors; JAKs phosphorylate STATs, which regulate gene expression.

GPCR signaling basics

GPCRs transmit signals via heterotrimeric G proteins to regulate adenylyl cyclase, phospholipase C, and more.

Protein phosphorylation

Addition of phosphate groups by kinases as a central mechanism for signal transduction.

GTP-binding proteins (G proteins)

Molecular switches that cycle between active GTP-bound and inactive GDP-bound states to propagate signals.

Protein kinase cascades

• Multistep signaling networks where receptor activation triggers sequential kinases to affect many targets.

• regulation of rapid AND/OR sustained cellular responses

Receptor downregulation

Process by which functional receptors are reduced, often via endocytosis and degradation.

Internalization and endosomes

Receptors are internalized into endosomes, which can lead to degradation or recycling.

Insulin signaling and glucose uptake

RTK-initiated pathway (IRS → PI3K → AKT) promoting glucose transporter (GLUT) translocation to the membrane.

Nuclear receptor structure

Domains include DNA-binding domain, ligand-binding domain, and transactivation domains; often function as dimers.