Ch 15: Cell Signaling

Flashcards related to cell signaling pathways and components, useful for exam preparation.

Cell Signaling Network

A sophisticated biological system within a cell that processes and interprets signals from its environment, enabling it to respond appropriately.

Signal Transducers

Molecules that convert extracellular signals into intracellular signals, leading to changes in the target cell's behavior.

Signaling Proteins as Switches

Proteins that are activated or deactivated temporarily through processes like phosphorylation or GTP binding to control cellular processes.

Target Cells

Cells that can adjust their responses to extracellular signals, allowing for fine-tuned control of cellular behavior.

Positive Feedback Loops

Mechanisms that amplify a cellular response, creating an all-or-none effect or converting a short signal into a long-lasting one.

Negative Feedback

A regulatory mechanism that allows cells to adapt to a signal, maintaining sensitivity to small changes in signal concentration over a broad range.

G-protein-coupled receptors (GPCRs)

A large family of cell-surface receptors that mediate responses to various signals, including hormones, neurotransmitters, and sensory stimuli.

GPCR Signal Molecules

A diverse group of molecules that activate GPCRs, including proteins, peptides, amino acid derivatives, fatty acids, and photons of light.

GPCR Sequestration

The process where GPCRs are internalized, reducing their availability to interact with ligands.

Receptor Destruction

The degradation of internalized receptors in lysosomes, removing them from the cell surface.

GPCR kinases (GRKs)

Enzymes that phosphorylate activated GPCRs, initiating a process of desensitization.

Arrestin Binding - First role in desensitization

Arrestin binding prevents the activation of the receptor from interacting with G proteins (stopping the signal).

Arrestin Binding - Second role in desensitization

Arrestin acts as an adaptor protein, linking the receptor to the endocytosis machinery for receptor-mediated endocytosis.

GPCRs

Cell-surface receptors that can indirectly activate or inactivate enzymes or ion channels via G proteins.

Adenylyl Cyclase

An enzyme that produces cyclic AMP, a second messenger that alters intracellular signaling pathways.

Phosphoinositide-specific phospholipase C (PLC)

An enzyme that generates inositol 1,4,5-trisphosphate (IP3) and diacylglycerol, two second messengers involved in cell signaling.

Inositol 1,4,5-trisphosphate (IP3)

A second messenger that releases Ca2+ from the ER, increasing cytosolic Ca2+ concentration.

Diacylglycerol

A second messenger that remains in the plasma membrane and helps activate protein kinase C (PKC).

PKC, PKA, and CaM-kinases

Enzymes that phosphorylate specific target proteins, modifying their activity and influencing cellular processes.

GPCR inactivation

A process where activated GPCRs are deactivated through phosphorylation and association with arrestins.

Enzyme-coupled receptors

Transmembrane proteins that bind ligands on the cell surface and activate intracellular enzymatic activity or associate with enzymes.

Receptor Tyrosine Kinases (RTKs) activation

Activation of tyrosine kinase domains leads to phosphorylation of tyrosine residues, initiating intracellular signaling cascades.

Smurf

An E3 ubiquitin ligase that ubiquitinates receptors, leading to their internalization and degradation.

Type-II receptors

Receptors that activate kinase domains and phosphorylate R-Smads, such as Smad2 and Smad3, in response to ligand binding.

Notch Protein

A type of transmembrane receptor, activated by cleavage upon binding to Delta proteins on another cell.

Cleaved cytosolic tail of Notch

A component that translocates to the nucleus to promote the expression of Notch-responsive genes.

Notch Protein

Acts as a signaling receptor, activating when it binds to Delta proteins expressed on adjacent cells.

Signaling through the Notch protein

A signaling pathway where latent transcription regulators are activated by cleavage following the binding of Delta proteins, influencing gene transcription.

KaiB

A protein that inhibits KaiA's stimulatory effect, allowing KaiC to dephosphorylate and reset the circadian clock.

Circadian clocks

Internal timekeeping mechanisms that generate 24-hour oscillations in cellular activities, anticipating daily environmental changes.

Plant Receptors

In plants rely mainly on enzyme-coupled receptors of the receptor serine/threonine kinase type, especially those with extracellular leucine-rich repeats.

Ethylene

A gaseous plant hormone that regulates gene transcription via intracellular receptors, influencing various developmental processes.

Phytochrome

A dimeric protein kinase that phosphorylates itself and activates transcription regulatory proteins in response to red light.

Phototropin

A protein associated with the plasma membrane, it mediates phototropism, the growth of plants toward light.

Cryptochromes

Flavoproteins that are sensitive to blue light and regulate various plant responses, related to blue-light-sensitive enzymes.