16.2 Flashcards
What are the 3 main types of Cell-Surface receptors?
- G Protein-Coupled Receptors
- Enzyme-Coupled Receptors
- Ion Channel-Coupled Receptors
What is the largest family of cell-surface receptors?
G Protein-Coupled Receptors
around how much of all drugs target GPCR?
50%
GPCRs bind a variety of signals and link to different G proteins to do what?
activate second messenger pathways
What do GPCRs do, in order to activate second messenger pathways?
bind a variety of signals and link to different G proteins
What are GPCRs?
Cell surface receptors that interact with G proteins to propagate signals
What are G Proteins?
Intracellular proteins acting as switches when bound to GTP/GDP
What is Adenylyl Cyclase?
The enzyme catalyzing the conversion of ATP to cAMP
What is cAMP?
A second messenger involved in signal transduction
What is Phospholipase C (PLC)?
The enzyme generating IP3 and DAG
What is the role of IP3?
Releases Ca2+ from the ER
What is the role of DAG?
Activates PKC for further signaling
What are RTKs (Receptor Tyrosine Kinases) ?
Cell surface receptors triggering protein cascades upon activation
G Proteins are composed of what 3 subunits?
α, β, and γ
What is the process that occurs when G proteins act at molecular switches?
GPCR activation triggers G protein binding, causing GDP to exchange for GTP, activating the α-subunit
What happens to activated subunits?
They can dissociate and regulate target proteins; the α-subunit’s intrinsic GTPase activity controls activation duration
What are the 2 mechanisms of G-Protein regulation?
Ion Channels & Membrane-bound Enzymes
The Membrane-Bound Enzymes consist of what?
the activation of
- adenylyl cyclase
(which produces cAMP)
-phospholipase C
(which produces IP3 & DAG)
What is the process of the cAMP signalling cascade?
G Protein Activation - Adenylyl Cyclase Activation - cAMP synthesis - PKA Activation
cAMP Signalling Cascade leads to what?
rapid responses like glycogen breakdown, and can trigger gene transcription for prolonged responses
What is the process of the IP3 and DAG signalling pathway?
G Protein - Phospholipase C activation - IP3 and DAG synthesis
The IP3 then triggers the release of Ca2+ from the ER, while DAG activates PKC for further signal propagation
What is the role of Ca2+ Signalling?
functions as a secondary messenger involved in muscle contraction, NT release, and cell secretion through its interaction with proteins like calmodulin
What is the largest class of Enzyme Coupled Receptors?
RTKs: Receptor Tyrosine Kinases
What do RTKs do?
Phosphorylates tyrosine residues on intracellular proteins
What is the structure of an Enzyme-Coupled Receptor?
Single transmembrane proteins with extracellular ligand-binding domain, and an intracellular enzyme-associated domain.
How are RTKs activated?
through dimerization, enabling phosphorylation and recruitment of signalling complexes
What is the Ras Protein?
a Monomeric GTP-binding protein, which acts as a molecular switch
What does the Ras Protein do?
activates a MAP kinase cascade, which is essential for cell proliferation/differentiation; implicated in ~30% of human cancers
What is DAG, what does it do?
Diacylclycerol; Activates PKC for further signaling
What are RTKs, what do they do?
Receptor Kinase Receptors; Cell surface receptors that trigger protein cascades upon activation
