Week 9 - Cell Signalling Flashcards
What is cell signaling
Process a cell uses to interact with itself, other cells and the environment
Cell signaling involves a signal, the receptor and the effector
What are the key elements of cell signalling
- signal
-receptor - effector
What is the signal in cell signaling
Any molecule, molecule complex or physical stimulus that conveys information from one cell to another to initiates a cellular response
What is a receptor in cell signalling
A specialized protein molecule or complex located either on the cell surface, within the cytoplasm or in the nucleus that binds to specific signaling molecules (ligands) and initiates a cellular response
Receptors only connects to specific ligands to cause an effect.
What is the effector in cell signaling
A molecule, protein or cellular component that executes or mediates the cellular response triggered by a signaling pathway.
What are examples of signals that can activate a receptor
- low blood glucose
- increase in body temperature
- release of neurotransmitter
- detection of a microorganism in the body - pathogen
- lack of red blood cells
How is maintaining homeostasis an example of cell signalling
Body temperature is normally 37 degrees and a negative feedback loop is initiated when the temperature changes.
Signal = temperature rising
Receptor = Hypothalamus
Effect = blood vessels dilating, sweating
This results in the heat being loss and body temperature returning to normal.
What are ligands
molecule that binds to receptors , thee are the signals.
What is signal transduction
Signal Transduction is the process that transmits a signal inside the cell through a series of events. Its a biochemical cascade of different molecules bringing signaled along a pathway.
What is post translational modification
This is the covalent modification of proteins after they have been synthesized in translation. Post-translation modification plays a crucial role in regulating protein structure, function, localization and activity.
What is a type of post translational modification
Phosphorylation and de-phosphorylation
What are the 4 types of receptors
- Ligand-gated Ion Channels
- G protein-coupled receptors (metabotropic)
- Kinase-linked receptors
- Nuclear receptors
What are ligand gated ion channels as a receptor
Ligand binding to ion channel receptors induce conformational changes that open or close the ion channel pore, leading to changes in ion flux across the membrane and alterations in cellular excitability and signaling
- ions will move down the concentration gradient
- they can also generate an action potential
e.g. sodium potassium pump
What are G protein-coupled receptors as receptors
Consist of a cell surface receptor coupled to G proteins (guanine nucleotide-binding proteins), which has 7 transmembrane domains.
In the receptor when the ligand binds to the g protein it causes conformational changes which releases the g protein and the alpha and gamma subunits - which move away to activate other targets.
In the receptor the ligand binds to the GPCRs causing conformational changes that activate intracellular signaling pathways mediated by G proteins, leading to the modulation of second messengers (cAMP, calcium ions) and the activation of downstream effectors.
What type of receptor can generate a second messenger
G protein coupled receptor
Example of a second messenger
cAMP
cyclic AMP
What are kinase linked receptors
Also known as enzyme linked-receptors, these receptors are a class of cell surface receptors that possess intrinsic kinase activity in their cytoplasmic domains. When the ligand binds these receptors undergo phosphorylation to other proteins, initiating a intracellular signaling cascade for other pathways.
What are nuclear receptors
Receptors which regulate gene expression/translation, by ligand-activated transcription factors, modulating the transcription of target genes involved in various physiological processes.
The ligand acts as a transcription factor, interacting directly with DNA to stimulate transcription to produce mRNA.
What are the types of nuclear receptors
Type 1
Receptor in cytoplasm and it undergoes translocation to enter the nucleus
Type 2
Receptor found in nucleus
What are the 5 types of signaling
- Direct signalling (contact dependent)
- Autocrine Signalling
- Paracrine Signalling
- Neuronal Signalling
- Endocrine signalling
What is direct signaling
This signaling occurs when signaling molecules on the surface of one cell interacts directly with receptors on an adjacent cell through physical contact. this type of signaling relies on cell to cell contact and is mediated by membrane-bound ligands and receptors.
This types of signaling is required for coordinated signaling e.g. contraction of the heart - this occurs from molecules passing through gap junctions between heart cells
What is autocrine signaling
Autocrine signaling is a type of cell signaling in which a cell secretes signaling molecules that binds to receptors on its own cell surface or neighboring cells of the same type.
Cell signals to itself which initiates changes within the cell (mostly immune responses as it shuts down processes).
What is paracrine signaling
Paracrine signaling is a form of cell-cell communication in which a cell secretes signaling molecules (paracrine factors) into the extracellular space (not the blood stream), where they act locally on neighboring cells of a different type.
Signals:
- Cytokines and growth factors
- Neurotransmitters
- Nitric oxide
- Prostaglandins
What is neuronal signaling
- Its the process by which neurons transmit electrical and chemical signals to communicate with each other and with target cells, such as other neurons, muscle cells or gland cells.
- The electrical signal travels along the axon which is an excitable cell.
- Releases neurotransmitters
This results in neurotransmitters to be released, which are usually stored in vesicles. These neurotransmitters then bind to the next neuron or target cell.
Neuronal signaling is essential for the functioning of the nervous system, including sensory perception, motor control, cognition, and behavior.
Example of neural signaling
serotonin
- Serotonin (5-HT)is released
- Binds to 5-HT receptor (GPCR)
- Modulates mood, sleep, digestion, bone health, blood clotting
What is released during neuronal signaling
neurotransmitters
What is neuronal signaling an example of
paracrine signaling
What is endocrine signaling
Endocrine signaling involves cells releasing signaling molecules called hormones into the bloodstream, which then travel to distant target cells or tissues to elicit a response. This form of signaling allows for long range communication and coordination of physiological processes throughout the body.
Example of endocrine signaling
Insulin
- Insulin binds to enzymatic receptor
- Triggers movement of GLUT 4 to surface
- Allows influx of glucose
Will a chemical signal produce the same response in all cells that have a receptor for it?
No, it depends on the type of cell - different types of cells will induce different effects even if they bind to the same receptor
e.g. blood glucose. Insulin binding will allow uptake of glucose in all cells, liver cells will also make glycogen