Podcast
Questions and Answers
How does CaM influence cAMP levels within the cytosol when it binds to PDE1?
How does CaM influence cAMP levels within the cytosol when it binds to PDE1?
- It activates PDE1, which converts cAMP to AMP, reducing cAMP levels. (correct)
- It inhibits PDE1, leading to increased cAMP levels.
- It activates adenylyl cyclase, increasing cAMP production.
- It directly converts cAMP to ATP, increasing energy availability.
What is the correct sequence of events in muscle contraction regulation by Ca²+ and CaM?
What is the correct sequence of events in muscle contraction regulation by Ca²+ and CaM?
- Myosin is phosphorylated -> CaM activates Ca2+ influx -> Ca2+ binds to MLCK.
- Intracellular Ca2+ rises -> Ca2+ binds to CaM -> CaM-Ca2+ activates MLCK -> MLCK phosphorylates myosin. (correct)
- CaM binds to myosin light chain kinase (MLCK) -> intracellular Ca2+ rises -> MLCK phosphorylates myosin.
- MLCK phosphorylates CaM -> Ca2+ binds to MLCK -> myosin binds to actin.
What role does CaMKII play in CREB-mediated gene transcription?
What role does CaMKII play in CREB-mediated gene transcription?
- It recruits p300 and CBP to silence gene transcription.
- It inhibits the dimerization of CREB, preventing DNA binding.
- It directly binds to CRE sequences on DNA, initiating transcription.
- It phosphorylates CREB, enabling it to dimerize and bind to CRE sequences. (correct)
Which mechanism describes Ca²+’s role in glycogen degradation?
Which mechanism describes Ca²+’s role in glycogen degradation?
How does increased intracellular Ca2+ affect glycogen synthesis?
How does increased intracellular Ca2+ affect glycogen synthesis?
Which subunit of phosphorylase kinase directly binds to calmodulin (CaM)?
Which subunit of phosphorylase kinase directly binds to calmodulin (CaM)?
Which of the following accurately depicts the effect of increased cAMP levels on glycogen metabolism?
Which of the following accurately depicts the effect of increased cAMP levels on glycogen metabolism?
What is the functional consequence of CaM binding to Ca2+?
What is the functional consequence of CaM binding to Ca2+?
How does CaM activation of myosin light chain kinase (MLCK) contribute to smooth muscle contraction?
How does CaM activation of myosin light chain kinase (MLCK) contribute to smooth muscle contraction?
How does CaM regulate CREB protein activity to stimulate transcription of various genes?
How does CaM regulate CREB protein activity to stimulate transcription of various genes?
How does the CaM-mediated activation of PDE1 lead to the downregulation of cAMP-dependent signaling pathways?
How does the CaM-mediated activation of PDE1 lead to the downregulation of cAMP-dependent signaling pathways?
What role does diacylglycerol (DAG) play in the context of calcium's effect on glycogen metabolism?
What role does diacylglycerol (DAG) play in the context of calcium's effect on glycogen metabolism?
How does the activation of glycogen phosphorylase affect glycogen metabolism?
How does the activation of glycogen phosphorylase affect glycogen metabolism?
Which of the following is the MOST direct effect of CaM's activation on gene expression?
Which of the following is the MOST direct effect of CaM's activation on gene expression?
How does CaM-Ca2+ binding influence the cellular concentration of cAMP?
How does CaM-Ca2+ binding influence the cellular concentration of cAMP?
How does increased intracellular Ca2+ promote glycogen degradation?
How does increased intracellular Ca2+ promote glycogen degradation?
Which process is LEAST directly regulated by CaM?
Which process is LEAST directly regulated by CaM?
Under what conditions would CaM MOST likely activate PDE1?
Under what conditions would CaM MOST likely activate PDE1?
Which of the following responses would be LEAST likely to occur following CaM activation?
Which of the following responses would be LEAST likely to occur following CaM activation?
How does CaM activation affect the activity of glycogen synthase?
How does CaM activation affect the activity of glycogen synthase?
Flashcards
What is Calmodulin (CaM)?
What is Calmodulin (CaM)?
Calmodulin (CaM) is a protein that binds calcium ions (Ca2+).
Function of CaM
Function of CaM
In its calcium-bound state, calmodulin (CaM) binds to CaM kinases and other proteins to trigger diverse cellular responses.
What is MLCK?
What is MLCK?
Myosin light chain kinase (MLCK) is a kinase activated by CaM-Ca2+ that phosphorylates the light chain of myosin, promoting muscle contraction.
What activates PDE1?
What activates PDE1?
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What is CaMKII?
What is CaMKII?
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What does increased intracellular Ca2+ do?
What does increased intracellular Ca2+ do?
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How does Ca2+ affect glycogen metabolism?
How does Ca2+ affect glycogen metabolism?
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Is Calmodulin part of phosphorylase kinase?
Is Calmodulin part of phosphorylase kinase?
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What happen after phosphorylation of CREB?
What happen after phosphorylation of CREB?
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Study Notes
- Calmodulin (CaM) is a protein that binds to Ca2+.
- When bound to Ca2+, CaM binds to CaM kinases and other proteins, eliciting diverse responses.
Calmodulin Targets
- CaM phosphorylates the myosin light chain, converting myosin from an inactive to an active state.
- CaM phosphorylates and activates CREB protein, permitting phosphorylated CREB protein to stimulate transcription of various genes.
- CaM binds to PDE1 to increase its activity, reducing cAMP levels in the cytosol.
Regulation of Muscle Contraction
- A rise in intracellular Ca2+ causes Ca2+ to bind to CaM.
- CaM-Ca2+ activates myosin light chain kinase (MLCK), a CaM kinase.
- MLCK phosphorylates the light chain of myosin, causing it to bind to actin and initiate muscle contraction.
Regulation of CREB Transcriptional Activity
- A rise in intracellular Ca2+ causes Ca2+ to bind to CaM.
- CaM-Ca2+ activates CaMKII, a CaM kinase.
- CaMKII enters the nucleus through the pores and phosphorylates CREB.
- CREB dimerizes, binds to DNA at CRE sequences, and recruits p300 and CBP to activate gene transcription.
Regulation of cAMP Levels
- A rise in intracellular Ca2+ causes Ca2+ to bind to CaM.
- CaM-Ca2+ activates calcium-calmodulin dependent phosphodiesterase 1 (PDE1).
- PDE1 is highly expressed in the brain, heart, and lung.
- PDE1 converts cAMP (produced by adenylyl cyclase) to AMP, downregulating cAMP-dependent signaling pathways.
Calcium Effect on Glycogen
- Calcium acts to inhibit glycogen synthesis and activate its degradation.
- PKC is activated through a Gq receptor, ultimately inhibiting glycogen synthase activity and synthesis of glycogen.
- An increase in intracellular Ca2+ leads to activation of phosphorylase kinase, which then activates glycogen phosphorylase.
- A rise in intracellular Ca2+ inhibits glycogen synthesis (via PKC) and activates glycogen degradation (via Ca2+).
Summary of Second Messengers
- cAMP, IP3, and DAG affect glycogen metabolism.
- GS = glycogen synthase
- GPK = glycogen phosphorylase kinase
- GP = glycogen phosphorylase
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