29 Questions
What is the primary goal of signal transduction?
To convert extracellular signals into a language that the inside of the cell can understand
Which type of signaling molecules reach neighboring target cells by passive diffusion?
Nitric oxide (NO)
What is the role of nitric oxide (NO) in signal transduction?
To initiate specific cellular responses in target cells
Which type of signaling molecule is synthesized from the amino acid arginine by the enzyme nitric oxide synthase?
Nitric oxide (NO)
What are the two types of signaling molecules mentioned in the text?
Extracellular and intracellular molecules
What is the time of action for paracrine signaling?
Short-term
What is the process of converting extracellular signals into a language that the inside of the cell can understand called?
Signal transduction
In the MAP kinase pathway, what activates the ERK family of kinases?
MEK
What is the function of Ras proteins in the MAP kinase pathway?
Activating the ERK family of kinases
Which pathway provides a more immediate connection between protein-tyrosine kinases and transcription factors?
JAK/STAT pathway
What is the central role of ERK activation in the MAP kinase pathway?
Inducing immediate-early gene expression
What is the key element in the JAK/STAT pathway?
STAT proteins
What happens to STAT proteins upon stimulation of cytokine receptors in the JAK/STAT pathway?
They translocate to the nucleus
What is the function of JAK protein tyrosine kinases in the JAK/STAT pathway?
Phosphorylating STAT proteins
What is the role of MEK in the MAP kinase pathway?
Activating the ERK family of kinases
Which type of G-protein activates cyclic-AMP formation within a cell?
Stimulatory G-protein (Gs)
What is the function of Phosphodiesterases in signal transduction?
Catalyze the hydrolysis of cAMP to AMP
What is the role of IP3 in signal transduction?
Releases Ca2+ from the endoplasmic reticulum
Which cell surface receptor family has a common structural motif with 7 transmembrane helices?
Rhodopsin-like receptors
What activates Ga-GTP to activate Adenylate Cyclase (AC) in signal transduction?
Binding of GTP to the Gα subunit
What is the function of Protein Kinase A (PKA) in signal transduction?
Catalyzes the transfer of phosphate from ATP to serine or threonine residues
What is the role of Phosphatidylinositol4,5-bisphosphate (PIP2) in signal transduction?
Activates Protein Kinase C (PKC)
Which molecule acts as a secondary messenger and can act as a reactive or free radical, causing the relaxation of vascular smooth muscle cells and stimulating macrophages to kill tumor cells and bacteria?
NO (Nitric Oxide)
Which type of signaling refers to the action of signaling molecules on their own cells, such as GF, cytokines, interferon, and interleukin?
Autocrine signaling
What is the type of cell surface receptor that directly phosphorylates their substrate proteins on tyrosine residues?
Receptor protein-tyrosine kinases
Which molecule is formed from GTP by guanylyl cyclase and activated by nitric oxide, carbon monoxide, and peptid ligands, leading to various responses such as blood vessel dilation?
cGMP
What activates adenylate cyclase to form cAMP by the catalysis of ATP?
Certain hormones binding to the outer surface of a cell
Which secondary messenger is degraded to AMP by cAMP phosphodiesterase?
cAMP
What is the largest family of cell surface receptors that transmit signals intracellularly via G proteins?
G-protein-coupled receptors
Study Notes
- NO (Nitric Oxide) is a secondary messenger that binds to and stimulates the activity of guanyl cyclase, leading to the production of cGMP and resulting in muscle cell relaxation and blood vessel dilation.
- Endocrine signaling refers to the process of hormones secreted by endocrine cells and reaching target cells through blood circulation, with long-lasting effects. Examples include insulin and adrenaline.
- Autocrine signaling is the action of signaling molecules on their own cells, such as GF, cytokines, interferon, and interleukin.
- G-protein-coupled receptors are the largest family of cell surface receptors, transmitting signals intracellularly via G proteins, with over a thousand identified.
- G proteins consist of three subunits: α (20 different genes), β (5 different genes), and γ (12 different genes).
- Binding of a hormone to its receptor promotes the interaction of the receptor with a G protein, leading to the activation and dissociation of the G protein α subunit, which then stimulates adenylyl cyclase and the production of cAMP.
- Neurotransmitters, such as acetylcholine, dopamine, and adrenaline, are secreted by neuronal cells and reach another neuron by the synaptic gap, with short-term effects. They also act as hormones in some cases.
- Receptor protein-tyrosine kinases are a type of cell surface receptor that directly phosphorylates their substrate proteins on tyrosine residues, with growth factors such as PDGF and EGF being examples.
- Secondary messengers, such as Ca2+, IP3, cAMP, and cGMP, act as intracellular molecules between the receptor region and the target intracellular effect region, causing intracellular chemical changes.
- NO is a secondary messenger that can act as a reactive or free radical, causing the relaxation of vascular smooth muscle cells and stimulating macrophages to kill tumor cells and bacteria by binding to the heme region of guanyl cyclase and inducing its activity.
- Ca2+ can act as a second messenger in both G-protein and tyrosine kinase pathways, with low levels in the cytoplasm and sources including the extracellular environment and ER.
- cAMP is a secondary messenger formed by the catalysis of ATP to cAMP by adenylate cyclase, activated by certain hormones binding to the outer surface of a cell. It has various effects, including glycogenolysis in skeletal muscle and liver, strengthening muscle contraction in cardiac muscle, and inhibiting contraction in smooth muscle.
- Protein kinases and phosphatases are regulated by complex signal cascades, with some being activated by Ca++-calmodulin and protein kinase A being activated by cAMP.
- cAMP is degraded to AMP by cAMP phosphodiesterase, with the phosphodiesterase being activated by phosphorylation catalyzed by protein kinase A.
- cGMP is another important secondary messenger formed from GTP by guanylyl cyclase and degraded to GMP by a phosphodiesterase. It is activated by nitric oxide, carbon monoxide, and peptid ligands, leading to various responses such as blood vessel dilation.
- The absorption of light by retinal activates the G-protein-coupled receptor rhodopsin, leading to the activation of G protein transducin and a decrease in intracellular cGMP levels, which is then translated to a nerve impulse by a direct effect on ion channels in the plasma membrane.
- Most signal molecules bind to receptors embedded in the plasma membrane and undergo a signal cascade to reach their intracellular targets. Only steroid hormones can directly interact with intracellular receptors.
Test your knowledge about cell surface receptors, G-proteins, and signaling pathways with this quiz. Learn about the common structural motif of 7 transmembrane helices and the activation of Gs protein by hormones like epinephrine and glucagon.
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