Cell Signaling and Communication

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary role of stimulatory G-proteins (Gs) in relation to cAMP?

Hydrolyzes GTP to deactivate cAMP production.

Inhibits adenylyl cyclase activity.

Transfers ADP ribose to NAD+.

Activates adenylyl cyclase for cAMP production. (correct)

Which of the following effects does cholera toxin have on G-proteins?

It ADP ribosylates Gs, preventing it from hydrolyzing GTP. (correct)

It prevents the activation of adenylyl cyclase.

It increases the hydrolysis of GTP.

It enhances the inhibitory effects of Gi proteins.

What is the role of PKA in relation to gene transcription?

It inhibits the transcription of somatostatin.

It directly synthesizes cAMP.

It activates CRE-binding proteins to initiate transcription. (correct)

It binds to G-proteins to enhance their activity.

What is the consequence of increased levels of cAMP in the cytosol?

It activates PKA, promoting various cellular responses. Signup and view all the answers

How does pertussis toxin affect G-proteins?

It ADP ribosylates the α subunit of Gi, preventing interaction with GPCR. Signup and view all the answers

What role do Ras GTPase-activating proteins (Ras GAPs) play in Ras protein function?

They hydrolyze GTP to inactivate Ras. Signup and view all the answers

Which kinase is referred to as MAPKK in the MAP kinase module?

Mek Signup and view all the answers

What occurs when a signal binds to a receptor in the Ras activation pathway?

RTK undergoes autophosphorylation. Signup and view all the answers

Which process indicates the transient activation of Ras observed in experiments?

Fluorescence Resonance Energy Transfer (FRET) peaking and declining. Signup and view all the answers

What effect does Ras-GEF have on Ras protein?

It activates Ras by replacing GDP with GTP. Signup and view all the answers

Which option is NOT a role of Rho family GTPases?

Facilitating receptor autophosphorylation. Signup and view all the answers

How do scaffolds in MAP kinase modules function?

They prevent cross-talk and organize kinases. Signup and view all the answers

Which of the following is correctly matched with its role in the Ras activation pathway?

Grb2 - Adaptor protein Signup and view all the answers

Which signaling pathway is primarily involved in promoting cell survival?

PI 3 Kinase pathway Signup and view all the answers

What do cytokine receptors primarily associate with to activate STATs?

Janus Kinases (Jaks) Signup and view all the answers

What is the role of phosphorylated Bad in the cell?

It activates apoptosis inhibitory protein. Signup and view all the answers

What type of proteins do cytokines control in immune response?

Immune cells Signup and view all the answers

What is produced by activated PI 3 Kinase as part of its signaling pathway?

PI(3,4,5)P3 Signup and view all the answers

How do inhibitory Smads affect R-Smads in the signaling pathway?

They compete with R-Smads for receptor binding. Signup and view all the answers

What occurs after the phosphorylation of the cytokine receptor?

It serves as a binding site for STAT. Signup and view all the answers

Which domain structure is characteristic of the Src family of cytoplasmic tyrosine kinases?

SH1 to SH4 domains Signup and view all the answers

What is the role of Ephexin in the signaling pathway activated by Ephrin A1 binding to EphA4?

Activates RhoA by exchanging GDP for GTP Signup and view all the answers

Which factor maintains Rheb in its inactive form when extracellular growth factors are absent?

Active Tsc2 Signup and view all the answers

What happens to mTOR when growth factors bind and activate the PI 3 Kinase - Akt pathway?

It becomes active by Rheb being in a GTP-bound state Signup and view all the answers

What does PI 3 Kinase produce that serves as docking sites for intracellular signaling proteins?

PI(3,4,5)P3 Signup and view all the answers

What is the function of RhoA once activated by Ephexin?

Facilitates actin filament contraction Signup and view all the answers

What do parallel signaling pathways highlight in cellular communication?

Common response mechanisms Signup and view all the answers

Which modification does phosphoinositide 2 Kinase NOT perform?

Dephosphorylates PI(4)P to PI(3,4)P2 Signup and view all the answers

How does RhoA activation affect cell behavior?

Triggers actin filament activation Signup and view all the answers

Which factor primarily influences the inactivation of CaM-Kinase II at low frequency Ca2+ spikes?

Immediate decrease in CaM-kinase activity Signup and view all the answers

What structural feature characterizes the primary cilium in rod photoreceptors?

Inner and outer segments specialized for signaling Signup and view all the answers

What is the effect of G12 activation on the cytoskeleton?

Regulation of actin cytoskeleton Signup and view all the answers

How does the frequency of Ca2+ spikes influence CaM-Kinase II activity?

Higher frequency maintains sustained activity Signup and view all the answers

Which G-protein's activation directly affects ion channels?

Gβγ Signup and view all the answers

What outcome occurs due to the activation of cyclic-nucleotide-gated ion channels?

Involvement in smell and sight Signup and view all the answers

Which signaling pathway is directly affected by vasopressin treatment?

Ca2+ oscillation pathway Signup and view all the answers

What role does phosphorylation play in Ca2+ oscillations?

It enhances Ca2+ sensitivity. Signup and view all the answers

What is the role of MLCK in the context of myosin filament formation?

It regulates myosin phosphorylation. Signup and view all the answers

Which structural feature characterizes microtubule assembly?

Microtubules have a hollow lumen. Signup and view all the answers

Which of the following best describes the orientation of tubulin subunits in microtubules?

α-tubulins are exposed at the minus end and β-tubulins at the plus end. Signup and view all the answers

How many myosin genes are present in humans?

40 Signup and view all the answers

What is the primary function of myosins found in hair cells of the inner ear?

Facilitating microvilli movement Signup and view all the answers

What mechanism describes the rapid change between growth and shrinkage in microtubules?

Dynamic instability. Signup and view all the answers

Which of these best describes the arrangement of myosin molecules?

Myosin molecules have a common N terminus motor domain. Signup and view all the answers

What role does GTP hydrolysis play in non-muscle cells?

It is converted to GDP, facilitating myosin filament assembly. Signup and view all the answers

Study Notes

Cell Signaling

Cells respond to various stimuli
External and internal signals affect cell structures, growth, reproduction, development, and behavior
Protein receptors receive these signals
Quorum sensing is coordinated behavior in bacteria at higher population densities via chemical signals leading to motility, antibiotic production, spore formation, or sexual conjugation.

Yeast Cell Communication

Saccharomyces cerevisiae multiply by budding
Cells send mating factors to stop budding and perform conjugation
Diploid zygote formation allows genetic material combination and shuffling during spore formation.

Cell Communication in Multicellular Organisms

Utilize chemical signals
Receptive proteins (membrane or cytosolic) receive signals
Intracellular signaling pathways or systems are activated by the binding of the signal to receptor
Effector proteins including transcription factors, ion channels, metabolic enzymes, signaling proteins, and cytoskeletons are impacted
Leads to changes in cell metabolism, gene expression, shape, or movement.

Cell-Surface Receptors (and intracellular)

Extracellular signals are diverse (proteins, peptides, amino acids, nucleotides, steroids, retinoids, dissolved gases).
Cell-surface receptors recognize mostly large, hydrophilic signals
Intracellular receptors mostly recognize small, hydrophobic signals
Signals are at low concentrations with high affinity to bind to receptors
Ion-channel-coupled, G-protein-coupled, and enzyme-coupled receptors are described as different classes

Signaling by Phosphorylation

Signal turns on or off
Kinases add phosphate to proteins
Phosphatases remove phosphate from proteins

Signaling by GTP Binding

GTP binding proteins are responsible as the second messengers
The protein is turned on when GTP is bound
The protein is turned off when GTP is hydrolyzed to GDP.
Two types: Trimeric and Monomeric GTP-binding proteins

Second Messengers as Molecular Switches

Phosphorylation is the process of activating or deactivating second messengers
Protein kinases add phosphate and protein phosphatases remove phosphate which controls second messenger function.

Intracellular Signaling Complexes

Scaffold proteins group interacting signaling proteins to ensure efficiency, specificity, and robustness of the response
Pre-assembled signal complex proteins
Involved in signal pathways including activation of second messengers (phospholipids), complex assembly on scaffold proteins, and transient assembly of signal proteins following ligand binding.

Signaling Pathways

Signal processing often involves a series of responses due to second messengers
Signal integration is the ability of the cell to coordinate multiple inputs causing the effect to be the same even though multiple receptors are involved.
Cell responses are the results of integrated signal pathways (two or more different signals bind to different receptors for a common response)

Signal Turnover

Fast degrading signal molecules change their concentration quickly
Slow degrading signal molecules change their concentration proportionally more slowly

Feedback Mechanisms

Positive feedback results in outputs that perpetuate the signal, potentially causing an all-or-none response or bistable condition
Negative feedback results in outputs that inhibit further signaling, potentially producing a brief, sustained, or oscillating response

G- Proteins (and GPCR Receptors)

G-protein-coupled receptors (GPCRs) are the most common and diverse receptor type in terms of recognized signals (ligands).
GPCRs have seven transmembrane domains
Ligands are diverse; including hormones, neurotransmitters, light sensitive materials, and those with smell and taste
Approximately 800 GPCRs are present in humans and over 1000 in mice.
These receptors mediate variety of functions and ~half of all known drugs, bind to GPCRs

Cyclic AMP (cAMP) as Second Messenger

CAMP is produced from ATP by adenyl cyclase.
Activation of cAMP-dependent protein kinases is mediated by cAMP.
cAMP-mediated effects can result in long term changes in cells.

G-proteins (Gs and Gi)

Stimulatory G proteins (Gs) activate adenylyl cyclase and cAMP production.
Inhibitory G proteins (Gi) inhibit adenylyl cyclase and suppress cAMP production.

Calcium Waves in Fertilized Eggs

Fertilization triggers a wave of calcium release across the egg from the entry point of sperm
Ca2+-induced Calcium Release (CICR) involves a positive feedback loop
The wave of Ca2+ changes the egg surface preventing the entry of other sperm cells.

Calcium Signaling

Calcium can serve as signal mediators in cells.
Triggers muscle contraction, exocytosis, and other cellular processes
The role of Calcium is mediated thru proteins such as calmodulin and kinases.

Intermediate Filaments

Several types of intermediate filaments exist, each with specific functions and locations within the cell.
They include lamins, neurofilaments, vimentin, desmin, and keratins.
Mutations are associated with diseases.

Cell Migration

Actin-rich cortex crucial
Protrusion creation
Attachment to substratum
Traction which draws the rest of the cell forward is facilitated by forces from actin polymerization and myosin contraction.

Rac and Rho

Rac GTPase promotes actin network formation and reduces myosin II activity
Rho GTPase promotes more stress fiber formation and increases myosin II activity.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Explore the intricate world of cell signaling and communication in both unicellular and multicellular organisms. Understand how cells respond to various stimuli, the roles of protein receptors, and the mechanisms of coordination among bacteria and yeast. Dive into the pathways activated by chemical signals and learn about the effects on growth, reproduction, and behavior.