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Questions and Answers
What is the primary role of stimulatory G-proteins (Gs) in relation to cAMP?
What is the primary role of stimulatory G-proteins (Gs) in relation to cAMP?
Which of the following effects does cholera toxin have on G-proteins?
Which of the following effects does cholera toxin have on G-proteins?
What is the role of PKA in relation to gene transcription?
What is the role of PKA in relation to gene transcription?
What is the consequence of increased levels of cAMP in the cytosol?
What is the consequence of increased levels of cAMP in the cytosol?
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How does pertussis toxin affect G-proteins?
How does pertussis toxin affect G-proteins?
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What role do Ras GTPase-activating proteins (Ras GAPs) play in Ras protein function?
What role do Ras GTPase-activating proteins (Ras GAPs) play in Ras protein function?
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Which kinase is referred to as MAPKK in the MAP kinase module?
Which kinase is referred to as MAPKK in the MAP kinase module?
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What occurs when a signal binds to a receptor in the Ras activation pathway?
What occurs when a signal binds to a receptor in the Ras activation pathway?
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Which process indicates the transient activation of Ras observed in experiments?
Which process indicates the transient activation of Ras observed in experiments?
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What effect does Ras-GEF have on Ras protein?
What effect does Ras-GEF have on Ras protein?
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Which option is NOT a role of Rho family GTPases?
Which option is NOT a role of Rho family GTPases?
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How do scaffolds in MAP kinase modules function?
How do scaffolds in MAP kinase modules function?
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Which of the following is correctly matched with its role in the Ras activation pathway?
Which of the following is correctly matched with its role in the Ras activation pathway?
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Which signaling pathway is primarily involved in promoting cell survival?
Which signaling pathway is primarily involved in promoting cell survival?
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What do cytokine receptors primarily associate with to activate STATs?
What do cytokine receptors primarily associate with to activate STATs?
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What is the role of phosphorylated Bad in the cell?
What is the role of phosphorylated Bad in the cell?
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What type of proteins do cytokines control in immune response?
What type of proteins do cytokines control in immune response?
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What is produced by activated PI 3 Kinase as part of its signaling pathway?
What is produced by activated PI 3 Kinase as part of its signaling pathway?
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How do inhibitory Smads affect R-Smads in the signaling pathway?
How do inhibitory Smads affect R-Smads in the signaling pathway?
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What occurs after the phosphorylation of the cytokine receptor?
What occurs after the phosphorylation of the cytokine receptor?
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Which domain structure is characteristic of the Src family of cytoplasmic tyrosine kinases?
Which domain structure is characteristic of the Src family of cytoplasmic tyrosine kinases?
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What is the role of Ephexin in the signaling pathway activated by Ephrin A1 binding to EphA4?
What is the role of Ephexin in the signaling pathway activated by Ephrin A1 binding to EphA4?
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Which factor maintains Rheb in its inactive form when extracellular growth factors are absent?
Which factor maintains Rheb in its inactive form when extracellular growth factors are absent?
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What happens to mTOR when growth factors bind and activate the PI 3 Kinase - Akt pathway?
What happens to mTOR when growth factors bind and activate the PI 3 Kinase - Akt pathway?
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What does PI 3 Kinase produce that serves as docking sites for intracellular signaling proteins?
What does PI 3 Kinase produce that serves as docking sites for intracellular signaling proteins?
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What is the function of RhoA once activated by Ephexin?
What is the function of RhoA once activated by Ephexin?
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What do parallel signaling pathways highlight in cellular communication?
What do parallel signaling pathways highlight in cellular communication?
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Which modification does phosphoinositide 2 Kinase NOT perform?
Which modification does phosphoinositide 2 Kinase NOT perform?
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How does RhoA activation affect cell behavior?
How does RhoA activation affect cell behavior?
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Which factor primarily influences the inactivation of CaM-Kinase II at low frequency Ca2+ spikes?
Which factor primarily influences the inactivation of CaM-Kinase II at low frequency Ca2+ spikes?
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What structural feature characterizes the primary cilium in rod photoreceptors?
What structural feature characterizes the primary cilium in rod photoreceptors?
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What is the effect of G12 activation on the cytoskeleton?
What is the effect of G12 activation on the cytoskeleton?
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How does the frequency of Ca2+ spikes influence CaM-Kinase II activity?
How does the frequency of Ca2+ spikes influence CaM-Kinase II activity?
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Which G-protein's activation directly affects ion channels?
Which G-protein's activation directly affects ion channels?
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What outcome occurs due to the activation of cyclic-nucleotide-gated ion channels?
What outcome occurs due to the activation of cyclic-nucleotide-gated ion channels?
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Which signaling pathway is directly affected by vasopressin treatment?
Which signaling pathway is directly affected by vasopressin treatment?
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What role does phosphorylation play in Ca2+ oscillations?
What role does phosphorylation play in Ca2+ oscillations?
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What is the role of MLCK in the context of myosin filament formation?
What is the role of MLCK in the context of myosin filament formation?
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Which structural feature characterizes microtubule assembly?
Which structural feature characterizes microtubule assembly?
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Which of the following best describes the orientation of tubulin subunits in microtubules?
Which of the following best describes the orientation of tubulin subunits in microtubules?
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How many myosin genes are present in humans?
How many myosin genes are present in humans?
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What is the primary function of myosins found in hair cells of the inner ear?
What is the primary function of myosins found in hair cells of the inner ear?
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What mechanism describes the rapid change between growth and shrinkage in microtubules?
What mechanism describes the rapid change between growth and shrinkage in microtubules?
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Which of these best describes the arrangement of myosin molecules?
Which of these best describes the arrangement of myosin molecules?
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What role does GTP hydrolysis play in non-muscle cells?
What role does GTP hydrolysis play in non-muscle cells?
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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.
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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.
