Unit: Cell communication and Cell Cycle
Chapter: Changes in signal transduction pathway
Reference: Changes in signal transduction pathway, Causes of changes in signal transduction pathways, Environmental conditions
Mutation, Inhibitors, and activators-Changes in Insulin Signaling Pathways
Cancer-causing types of changes in signal transduction pathways
Learning Objectives
- To understand the cause of changes in signal transduction pathway
- To learn few examples of the effect caused due to these changes
Changes in signal transduction pathway
Signal transduction pathway (or signal cascade) refers to the branched molecular network that successively activates (or deactivates) signaling molecules to perform a certain biological function.
When there are changes or disruptions in signal transduction pathways, cellular response may be affected, or in worse cases, cause life-threatening diseases like cancer.
Causes of changes in signal transduction pathways
There are three major causes of change in signal transduction pathways: environmental conditions, mutations, inhibitors, or activators
Environmental conditions-When environmental conditions such as temperature or pH are altered beyond a limit then the proteins and enzymes are denatured. The structure of protein is changed and its is no longer able to carry out its function
Mutation– if there is any change in nucleotide sequences of DNA, then protein synthesis will not occur and in signal transduction pathway it is very much required. It will not be able to code for the gene.
Inhibitors and activators-A signal transduction pathway can be altered by a variety of inhibitors and activators, including substances like pesticides and some medications.
There are many kinds of inhibitors that have the power to alter an enzyme's role in a signal transduction pathway, including:
- Competitive inhibitors physically block the active site, preventing the substrate from entering.
- Non-competitive inhibitors bind to a different site on the enzyme but also hinder reaction catalysis.
On the other hand, activators are molecules that reversibly or irreversibly bind to receptor proteins. Activators can activate pathways that would not have been activated otherwise. Many pesticides, for example, are strong activators of signal transduction pathways in neurons, resulting in hyperactivity in insect brains and, eventually, death.
Changes In Insulin Signaling Pathways
- Insulin is a hormone which is produced in pancreas by the DNA stored in it. It reduces the blood sugar level.
- Insulin reaches to the target cell and bind to receptor protein and carry out reactions.
- This results in absorption of glucose from blood and goes to vesicle binding cell membrane, resulting in reduction of blood glucose levels
- The mutation in insulin alters its shape which results inability in reducing the blood sugar level which causes a condition called neonatal diabetes.
- More severe mutations, in this case, may also include fatal and chronic disorders such as Donohue syndrome, wherein cells do not respond to insulin, thus causing severe insulin aversion in the body.
Cancer-causing types of changes in signal transduction pathways
- The dysregulation of signal transduction pathways can be caused by oncogenic mutations which cause genes to be over expressed or produce proteins with dysregulated activities
- Another cause of dysregulation is the deletion or mutation of negative regulators which typically function as tumour suppressors, inactivating them.
- For example, one of the most common mutated genes is a tumour suppressor called p53 which regulates cell proliferation and stress signals that lead to apoptosis and damage responses.
- When p53 is lost due to deletion or mutation, it can contribute to cancer by reducing cell death and dysregulating the cell cycle.
Solved examples
Example 1. Signal amplification is most often achieved by—-
a) an enzyme cascade b) binding of multiple signals
c) branching pathways d) action of adenylyl cyclase
Solution 1: a. Signal amplification is most often achieved by an enzyme cascade.
Example 2. Programmed cell death is known as
a) mutation b) termination c) cytokinesis d) apoptosis
Solution 2: d. Programmed cell death is known as Apoptosis
Summary
- There are three major causes of change in signal transduction pathways: environmental conditions, mutations, inhibitors, or activators
- When environmental conditions such as temperature or pH are altered beyond a limit then the proteins and enzymes are denatured.
- When Mutations alter the nucleotide sequence, it disturbs the production of proteins and enzymes, thus disrupting the transduction pathway.
- The mutation in insulin alters its shape which results inability in reducing the blood sugar level which causes a condition called neonatal diabetes.
- The dysregulation of signal transduction pathways can be caused by oncogenic mutations which cause genes to be over expressed or produce proteins with dysregulated activities