Cell Signaling: Apoptosis, Auxin Pathways & Signal Transduction & Techniques in Cells Modules 13-14 Final

Cell Signaling

The process through which cells communicate with each other.

Extracellular Messenger Molecules

Molecules that facilitate communication between cells.

Autocrine Signaling

A type of signaling where a cell responds to the messenger it releases.

Paracrine Signaling

A type of signaling where messenger molecules travel short distances through extracellular space.

Endocrine Signaling

A type of signaling where messenger molecules reach their target cells through the bloodstream.

First Messenger/Ligand

A molecule that binds to the receptor.

Receptors

Proteins in target cells that receive an extracellular message.

Signal Transduction Pathways

Pathways activated by either a diffusible second messenger or recruitment of cytoplasmic proteins.

Effector

An enzyme that generates a second messenger in response to a signal.

Second Messengers

Small molecules that act as activators or inhibitors of specific proteins.

Protein Conformation

The three-dimensional shape of a protein, which is altered during signaling pathways.

Phosphorylation

The process of adding phosphate groups to proteins, altering their conformation.

Kinases

Enzymes that add phosphate groups to proteins.

Phosphatases

Enzymes that remove phosphate groups from proteins.

Human Genome

Encodes more than 500 protein kinases and approximately 150 protein phosphatases.

Soluble Cytoplasmic Proteins

Proteins that can be found freely in the cytoplasm, some of which are kinases or phosphatases.

Integral Membrane Proteins

Proteins that are embedded in the cell membrane, some of which are kinases or phosphatases.

G-protein Coupled Receptors

Receptors that play a key role in signaling pathways by activating G-proteins.

Heterotrimeric G Protein

A protein complex composed of three subunits (Gα, Gβ, Gγ) that binds to effector molecules.

Gα Subunit

The subunit of the heterotrimeric G protein that binds to the effector molecule to activate it.

Gβ Subunit

One of the three subunits of the heterotrimeric G protein, involved in signaling.

Gγ Subunit

One of the three subunits of the heterotrimeric G protein, involved in signaling.

Signal transduction pathway

A pathway consisting of protein kinases and protein phosphatases with catalytic actions that change the conformations, and thus the activities, of the proteins they modify.

Protein phosphorylation

A process that can change protein behavior in different ways by activating or inactivating an enzyme, increasing or decreasing protein-protein interactions, changing the subcellular location of the protein, or triggering protein degradation.

Changes in cellular activities

Includes changes in gene expression, alteration of the activity of metabolic enzymes, reconfiguration of the cytoskeleton, an increase or decrease in cell mobility, changes in ion permeability, activation of DNA synthesis, and cell death.

Extracellular messengers

Include small molecules such as amino acids and their derivatives, gases, steroids, eicosanoids, and various peptides and proteins.

G-protein coupled receptors (GPCRs)

The largest superfamily of proteins encoded by animal genomes, characterized by seven α-helical transmembrane domains and the ability to interact with heterotrimeric G Proteins.

Natural ligands for GPCRs

Include hormones (both plant and animal), neurotransmitters, opium derivatives, and chemoattractants (odorants, tastants, and photons).

Physiological response

The outcome of ligand activation of receptors that stimulate effectors, resulting in a specific physiological effect.

Epinephrine

A ligand that activates the beta-Adrenergic receptor, stimulating adenylyl cyclase and resulting in glycogen breakdown.

Serotonin

A ligand that activates the serotonin receptor, stimulating adenylyl cyclase and resulting in behavioral sensitization and learning in Aplysia.

Light

Stimulates rhodopsin, leading to activation of cGMP phosphodiesterase and visual excitation.

IgE-antigen complexes

Activate the mast cell IgE receptor, stimulating phospholipase C and resulting in secretion.

f-Met peptide

A ligand that activates the chemotactic receptor, stimulating phospholipase C and resulting in chemotaxis.

Acetylcholine

A ligand that activates the muscarinic receptor, stimulating a potassium channel and resulting in slowing of pacemaker activity.

Steroid hormones

Regulate sexual differentiation, pregnancy, carbohydrate metabolism, and excretion of sodium and potassium ions.

Eicosanoids

Nonpolar molecules derived from fatty acid, arachidonic acid, that regulate processes including pain, inflammation, blood pressure, and blood clotting.

Receptor protein-tyrosine kinases (RTKs)

A type of receptor involved in cell signaling that phosphorylates tyrosine residues on target proteins.

Ligand gated channels

Receptors that open or close in response to the binding of a ligand, allowing ions to flow across the membrane.

Steroid hormone receptors

Receptors that bind steroid hormones and mediate their effects on target cells.

Specific receptors

Receptors that are tailored to bind specific ligands and initiate a cellular response.

G Protein-Coupled Receptors (GPCRs)

Receptors that mediate signal transduction by binding ligands and activating G proteins.

Signal Transduction

The process by which a signal is transmitted through a cell via GPCRs and G proteins.

Ligand

A molecule that binds to a receptor to initiate a signal transduction pathway.

Gα subunit

The subunit of a G protein that releases GDP and binds GTP upon receptor activation.

Gβγ complex

The dimeric complex of G protein subunits that remains after Gα dissociates.

Adenylyl cyclase

An effector enzyme activated by Gα that converts ATP to cyclic AMP (cAMP).

Cyclic AMP (cAMP)

A second messenger produced by adenylyl cyclase that mediates various cellular responses.

Desensitization

The process that prevents active receptors from continuing to activate G proteins.

G protein-coupled receptor kinase (GRK)

An enzyme that phosphorylates active GPCRs, initiating desensitization.

Arrestin

A protein that binds to phosphorylated GPCRs to inhibit their activity and promote internalization.

Endocytosis

The process by which cells internalize receptors bound to arrestin.

Resensitization

The process by which recycled receptors return to the cell surface and regain sensitivity to ligands.

Clathrin-coated pits

Structures that facilitate the internalization of arrestin-bound GPCRs into the cytoplasm.

Endosomes

Membrane-bound compartments that contain internalized GPCRs and arrestins.

MAPK cascade

A signaling pathway that can be assembled by arrestins in endosomes.

Heterotrimeric G proteins

G proteins composed of three subunits (Gα, Gβ, Gγ) that mediate signal transduction.

GTP hydrolysis

The process by which Gα subunits turn themselves off by converting GTP to GDP and Pi.

Gs family

G protein family members that couple receptors to adenylyl cyclase.

Gq family

G protein family members that activate phospholipase C (PLCβ).

Gi subunits

G protein subunits that inhibit adenylyl cyclase activity.

G12/13 members

Less well-characterized members of the heterotrimeric G protein family.

Cholera toxin

A bacterial toxin that modifies Gα subunits to activate adenylate cyclase, causing intestinal water loss.

Pertussis toxin

A bacterial toxin that inactivates Gα subunits, inhibiting immune defense.

Effector molecule

The target molecule that is activated by the Gα subunit in the signaling pathway.

G-protein coupled receptors

Receptors that play a role in signaling pathways by activating G proteins upon binding with a ligand.

Signal transduction pathways

The process by which a cell responds to signals from outside its membrane, often involving a series of molecular events.

Cyclic AMP

A second messenger that is synthesized following the binding of a first messenger to a receptor, enabling a large-scale cellular response.

Second messengers

Molecules that relay signals received at receptors on the cell surface to target molecules inside the cell.

Phosphatidylinositol (PI)

A phospholipid that can be phosphorylated to form PIP2, which is involved in generating second messengers.

Phospholipase C-β (PLCβ)

An enzyme that splits PIP2 into inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG) in response to receptor activation.

Inositol 1,4,5-trisphosphate (IP3)

A second messenger that triggers calcium ion release from the smooth endoplasmic reticulum.

Diacylglycerol (DAG)

A second messenger that recruits protein kinase C (PKC) to the membrane and activates it.

Calcium ions (Ca2+)

Second messengers that bind to various target molecules, triggering specific cellular responses such as muscle contraction.

Phospholipases

Enzymes that convert phospholipids into second messengers by splitting lipid molecules.

Phosphoinositide kinases

Enzymes responsible for phosphorylating inositol molecules, contributing to the formation of second messengers.

Phospholipid kinases

Enzymes that phosphorylate phospholipids, converting them into active second messengers.

Phospholipid phosphatases

Enzymes that dephosphorylate phospholipids, playing a role in the regulation of second messenger pathways.

Study case

An assessment component worth 8% of the total grade.

Discussion board

An assessment component worth 5% of the total grade.

Exams

Assessment components that account for 69% of the total grade, consisting of four exams.

Quizzes

Assessment components that account for 10% of the total grade, consisting of ten quizzes.

Analytical assignments

Assessment components that account for 8% of the total grade, consisting of four assignments.

Final exam

The last assessment occurring between April 28th and May 1st, with no cumulative content from earlier modules.

Module 11-14

The content covered in the course that is not cumulative for the final exam.

Vascular smooth muscle

Contraction

Stomach smooth muscle

Contraction

Slime mold

Cyclic GMP formation, actin polymerization

Blood platelets

Shape change, aggregation

Salamander rods

Modulation of light response

Xenopus oocytes

Calcium mobilization, membrane depolarization

Sea urchin eggs

Membrane depolarization, cortical reaction

Lacrimal gland

Increased potassium current

Epinephrine binding to β-adrenergic receptor

Activates Gαs subunit, stimulates cAMP production, increases rate and force of contraction

Epinephrine binding to α-adrenergic receptor

Activates Gαi subunit, inhibits cAMP production, leads to muscle relaxation

Glucagon and epinephrine hormones

Bind to different receptors on the same cell, stimulate glycogen breakdown, inhibit its synthesis

cAMP

Activated by the G protein of both hormone receptors

cAMP-dependent protein kinase (PKA)

Activated by cAMP, phosphorylates specific proteins in response to stimuli

PKA substrates

Over 100 have been described, affected by changes in cAMP concentration

PKA-anchoring proteins (AKAPs)

Facilitate signaling complexes operating in different subcellular compartments