In this presentation we will look the different pathways that initiates and propagates a serial cascade events for prpper cellular response, i hope to be intrested, and please if there any suggest do not hasitate for writting a replay to me, thanks
2. Course outline
1) Signaling Through Ion Channels.
2) Signaling Through Enzyme And Enzyme
Coupled Receptors.
3) Signaling Through G Protein Coupled
Receptors.
4) Signaling Through Intracellular Receptors.
5) Signaling Through Receptors That Undergo
Cleavage
3. 1- Signaling Through Ion Channel
Receptors:
• An ion channel receptor is a type of plasma
membrane receptor that contains both a messenger-
binding site and an ion channel.
4. 2 a- Signaling Through Enzyme
Receptors:
• An enzyme receptor is a type of plasma
membrane receptor that contains a messenger-
binding site, a transmembrane segment, and a
site that functions as an enzyme.
• There are two major categories of enzyme
receptors:
1. Receptor tyrosine kinases.
2. Receptor guanylyl cyclases.
7. 2b- Signaling Through Enzyme-
Coupled Receptors:
• An enzyme-coupled receptor is a type of plasma
membrane receptor that contains a messenger-
binding site, a transmembrane segment, and a site
coupled to a separate enzyme.
• The enzyme coupled receptors has different types of
proteins compared to the other enzyme receptors
mention above.
• For many enzyme-coupled receptors, the enzyme
that is linked to the receptor is a janus kinase ( JAK), a
type of tyrosine kinase.
9. 3- Signaling Through G Protein-
Coupled Receptors:
• A G protein-coupled receptor is a type of plasma
membrane receptor that contains a messenger-
binding site, a transmembrane segment, and a
site coupled to a G protein.
• A G protein is a membrane protein that is so-
named because it binds guanosine nucleotides,
either guanosine diphosphate (GDP) or guanosine
triphosphate (GTP).
• Three subunits comprise a G protein: alpha (α),
beta (β), and gamma (γ).
10. These components of the G protein function in the following way:
• When the α subunit is bound to GDP, the G protein is inactive.
• Once a messenger activates a G protein-coupled receptor, the
receptor undergoes a conformational change that triggers the
α subunit of the G protein to release GDP in exchange for GTP.
The binding of GTP to the α subunit causes the G protein to
undergo a conformational change and become activated.
• Upon activation, the α subunit typically separates from the β
and γ subunits, which remain together as a βγ complex. Then
either the α subunit or βγ complex moves along the cytosolic
surface of the plasma membrane to alter the activity of a target
protein that is involved in the next step of the signal
transduction pathway.
11. A) G Protein Signaling Pathways That Use
Cyclic AMP as a Second Messenger:
cyclic AMP
Gs (s = stimulatory).
13. B) G Protein Signaling Pathways That Use IP3,
DAG, and Calcium as Second Messengers:
Phosphatidylinositol bisphosphate (PIP2).
Diacylglycerol (DAG).
Inositol trisphosphate (IP3).
14. C) G Protein Signaling Pathways That
Use phosphodiesterase
17. E) G Protein Regulation of Ion Channels:
• G protein regulating of ion channels either opens
or close ion channels.
• Many neurotransmitters activate G protein
signaling pathways that either:
• Directly (the G protein directly opens the ion
channel by binding to it)
• Indirectly regulate ion channels.
20. • These proteins, located in the cytosol or
nucleus, are ligand-activated transcription
factors.
• These receptors link extracellular signals to
gene transcription.
4- Signaling Through Intracellular
Receptors
23. C) Signaling pathway used by
Steroids:
Glucocorticoid
Heat shock protein
Glucocorticoid response element
24. • In response to ligand binding, some transmembrane
proteins undergo regulated intramembranous
proteolysis (RI), which liberates one or more fragments of
their cytosolic domain that signal a cellular response by
entering the nucleus to modulate gene expression.
5- Signaling through Receptors that
undergo cleavage: