Chapter 15 - Cell Communication Part 1: Nuclear Receptors & GPCRs Flashcards
What are intracellular signals?
Signals originating within the cell for rapid metabolic regulation.
What are extracellular signals?
Signals between cells, such as hormones, for metabolic integration.
Give examples of intracellular signals.
Fe metabolism, substrate availability, misfolded proteins.
Name examples of extracellular signals.
Hormones, neurotransmitters, growth factors.
What is autocrine signaling?
Cells responding to signals they release themselves.
Define paracrine signaling.
Signals acting locally between nearby cells.
What is endocrine signaling?
Hormones traveling through the bloodstream to distant cells.
How is signal specificity achieved in cell signaling?
Through ligand-receptor interactions.
Name three families of cell surface receptors.
GPCRs, receptor tyrosine kinases, ligand-gated ion channels.
Describe G-protein coupled receptors (GPCRs).
Receptors with seven transmembrane domains activating G proteins.
What is the role of receptor tyrosine kinases (RTKs)?
They phosphorylate tyrosine residues on signaling proteins.
What are nuclear receptors?
Intracellular receptors acting as transcription factors.
How does GPCR activation affect intracellular pathways?
It activates G proteins, triggering secondary messengers.
Name a second messenger produced by GPCRs.
Cyclic AMP (cAMP).
How is cAMP generated?
By adenylyl cyclase activated by G-proteins.
What is IP₃ and what does it do?
A second messenger that releases Ca²⁺ from the ER.
Describe the role of diacylglycerol (DAG) in signaling.
It activates protein kinase C (PKC).
What enzyme produces IP₃ and DAG?
Phospholipase C (PLC).
What role does Ca²⁺ play in signal transduction?
It acts as a messenger activating various kinases.
Define calmodulin.
A Ca²⁺-binding protein activating enzymes like CaM-kinase.
What is the function of CaM-kinase?
It mediates Ca²⁺-dependent signaling, critical for learning and memory.
Explain positive feedback in cell signaling.
It amplifies the response, leading to an all-or-none effect.
What is negative feedback in signaling?
A mechanism that reduces the response, aiding in signal desensitization.
What is receptor desensitization?
Reduction of receptor response after prolonged stimulation.
Give an example of a disease caused by disrupted RTK signaling.
Cancer, due to overactive receptor tyrosine kinases.
Name a drug class that targets GPCRs.
Beta-blockers, used in heart disease treatment.
How does receptor internalization affect signaling?
It removes receptors from the surface, reducing sensitivity.
What is adenylyl cyclase’s role in the cAMP pathway?
It converts ATP to cAMP, initiating signal transduction.
How does Ca²⁺ signaling affect muscle contraction?
It triggers contractions by activating contractile proteins.
Explain the fight-or-flight response at the molecular level.
Adrenaline activates GPCRs, raising cAMP, and triggering responses.
What does cholera toxin do to G-protein signaling?
Locks G-protein in active state, causing excessive cAMP production.
How do GPCRs influence heart rate?
They regulate K⁺ channels, altering the pace of cardiac contraction.
What type of receptor is the glucocorticoid receptor?
A nuclear receptor that binds cortisol and regulates gene transcription.
Define signal transduction.
The process by which a cell responds to extracellular signals via receptors.
What is the role of CREB in the cAMP pathway?
A transcription factor activated by PKA to regulate gene expression.
How does phosphorylation affect signaling proteins?
It activates or inactivates proteins, modifying cellular responses.
What is a ‘second messenger’ in cellular signaling?
A small molecule that relays signals inside the cell.
Why is Ca²⁺ considered a ubiquitous messenger?
It participates in numerous cellular processes across cell types.
What is the effect of IP₃ binding to its receptor?
It releases Ca²⁺ from intracellular stores, modulating cellular activities.
Describe the importance of signal amplification.
Ensures a strong response from a small signal input.
How does nitric oxide (NO) act as a signaling molecule?
It diffuses across membranes to activate guanylyl cyclase.
How do muscarinic Ach receptors affect cardiac cells?
They reduce heart rate by opening K⁺ channels via GPCR signaling.
What is the Wnt signaling pathway’s role in cell fate?
Regulates cell proliferation and differentiation through gene expression.
Name the three major classes of secondary messengers.
Cyclic nucleotides, IP₃/DAG, and Ca²⁺ ions.
How is cGMP different from cAMP in signaling?
cGMP often mediates visual and smooth muscle responses.
What is the function of arrestins in GPCR signaling?
They desensitize GPCRs, facilitating receptor internalization.
Describe Ras protein’s role in cell signaling.
A GTPase involved in cell growth signaling via RTKs.
How does receptor clustering influence signaling?
Increases the efficiency of signal transduction.
What are coincidence detectors in signaling?
Proteins that require two signals to initiate a response.
What is the physiological significance of GPCR diversity?
Allows cells to respond to a variety of ligands and signals.
