Examples of Wnt signaling pathway in the following topics:
-
- Many of these genes are involved in the Wnt signaling pathway.
- Wnt signaling can be implicated in the formation of the anteroposterior and dorsoventral axes.
- Wnt signaling activity in anterior-posterior development can be seen in several organisms including mammals, fish, and frogs.
- Wnt signaling is also involved in the axis formation of specific body parts and organ systems that are a part of later development.
- High Wnt signaling establishes the dorsal region while high Shh signaling indicates in the ventral region.
-
- Ligand binding to cell-surface receptors activates the receptor's intracellular components setting off a signaling pathway or cascade.
- After the ligand binds to the cell-surface receptor, the activation of the receptor's intracellular components sets off a chain of events that is called a signaling pathway or a signaling cascade .
- A single pathway can branch off toward different endpoints based on the interplay between two or more signaling pathways.
- Another complicating element is signal integration of the pathways in which signals from two or more different cell-surface receptors merge to activate the same response in the cell.
- An example of ligand initiated signaling pathways is when epidermal growth factor (EGF) binds to its receptor.
-
- Signal cascades convey signals to the cell through the phosphorylation of molecules by kinases.
- Ligand binding to the receptor allows for signal transduction through the cell.
- The chain of events that conveys the signal through the cell is called a signaling pathway or cascade.
- Signaling pathways are often very complex because of the interplay between different proteins.
- The aberrant signaling often seen in tumor cells is proof that the termination of a signal at the appropriate time can be just as important as the initiation of a signal.
-
- Visual signals are processed in the brain through several different pathways.
- Within the nerves, different axons carry different parts of the visual signal.
- When visual signals leave the thalamus, they travel to the primary visual cortex at the rear of the brain.
- From the visual cortex, the visual signals travel in two directions.
- Finally, there is the pathway from the retina to the suprachiasmatic nucleus (SCN) of the hypothalamus.
-
- Cell signaling pathways play a major role in cell division.
- Activation of RTKs initiates a signaling pathway that includes a G-protein called RAS, which activates the MAP kinase pathway described earlier.
- In addition, uncontrolled cell growth leads to cancer; mutations in the genes encoding protein components of signaling pathways are often found in tumor cells .
- Signaling pathways control cell growth.
- These pathways are controlled by signaling proteins, which are, in turn, expressed by genes.
-
- Signaling pathway induction activates a sequence of enzymatic modifications that are recognized in turn by the next component downstream.
- The induction of a signaling pathway depends on the modification of a cellular component by an enzyme.
- One of the most common chemical modifications that occurs in signaling pathways is the addition of a phosphate group (PO4–3) to a molecule such as a protein in a process called phosphorylation .
- The activation of second messengers is also a common event after the induction of a signaling pathway.
- A-kinase regulates many vital metabolic pathways.
-
- Metabolic regulation also allows organisms to respond to signals and interact actively with their environments.
- Two closely-linked concepts are important for understanding how metabolic pathways are controlled.
- Firstly, the regulation of an enzyme in a pathway is how its activity is increased and decreased in response to signals.
- For example, an enzyme may show large changes in activity (i.e. it is highly regulated), but if these changes have little effect on the rate of a metabolic pathway, then this enzyme is not involved in the control of the pathway.
- The result of one such signaling pathway affects muscle cells and is a good example of an increase in cellular metabolism.
-
- Bacterial signaling allows bacteria to monitor cellular conditions and communicate with each other.
- Because the number of cells present in the environment (the cell density) is the determining factor for signaling, bacterial signaling was named quorum sensing.
- Quorum sensing uses autoinducers as signaling molecules.
- The peptide autoinducers stimulate more complicated signaling pathways that include bacterial kinases.
- Describe how cell signaling occurs in single-celled organisms such as bacteria
-
- Binding of these hormones to a cell surface receptor results in activation of a signaling pathway; this triggers intracellular activity to carry out the specific effects associated with the hormone.
- The hormone that initiates the signaling pathway is called a first messenger, which activates a second messenger in the cytoplasm.
- The effect of a hormone is amplified as the signaling pathway progresses.
- Cellular responses to hormone binding of a receptor include altering membrane permeability and metabolic pathways, stimulating synthesis of proteins and enzymes, and activating hormone release.
- An enzyme called phosphodiesterase breaks down cAMP, terminating the signal.
-
- This patterning occurs early in development and results from the activity of several secreted signaling molecules.
- Sonic hedgehog (Shh) is a key player in patterning the ventral axis, while Bone morphogenic proteins (Bmp) and Wnt family members play an important role in patterning the dorsal axis.